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The YZ400 is not that great a bike!

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Posted by: A-Loop---------------------

Pick up any motorcycle magazine today and they'll tell you at length about what a fantastic machine the YZ400/426 is. Sent down from heaven on a beam of blue light, the Yamaha has it all; speed, agility, and most importantly, it has four separate strokes. It's true; everybody likes to twist the "loud handle" on a YZ. They look good, they sound good, they are sure fun to wheelie and they do accelerate like crazy, but is this machine really the phenomenon that everybody seems to think it is?**Or more realistically, are people just thrilled that the motor vehicle industry started to upgrade the technology of dirt bikes?**I may be the only one, who feels this way, but to me, the YZ400 is a long way from being the perfect fourstroke, much less the perfect two-wheeled missile that everyone seems hypnotized into believing. Let me explain why.

I hold dirt bikes up to be measured by three fundamental rules.

Fundamental number one is this; weight always hurts you; it never helps. With all the advancements in our sport in the last decade, how everyone can make such a fuss over a bike that still weighs nearly 280 lbs wet is just beyond me. When you look at the complexity issue, and then factor in what it does to the weight of the machine, it is even clearer that the YZ is not the heaven-sent perfect bike. You know your buddy that's totally into mountain bikes? He spends hundreds and hundreds of dollars on lighter parts just to save a few GRAMS! And we load our dirt bikes up with about every gizmo that the engineers, (or is it the sales department) can think up. In 1975 we had dirt bikes that weighed less than 200lbs, don't tell me that we can't design one today. Really, if you use a chromemoly frame, keep the engine's overall size down by using a three or four-speed tranny, and make an effort to design things smaller and lighter rather than the other way around, it can be done. I'd enjoy seeing some exotic metals like carbon fiber rods and ceramic pistons; maybe even some Ti now that Russia is selling it for far less money. What is the weight of a stock YZ engine now, something like 90 lbs? Let's try to get that down to about 50, (which is still 10 lbs heavier than a 250 twostroke). Then see how it feels to fly on a bike that's only 210lbs, rather than 280.

Fundamental rule number 2 is that complexity will always return to bite you in the ass. Take a look at the YZ engine for a minute. Five valves, two cams, a computer controlled carb, and more wires, hoses, and gadgets than my Ford van. Friends, what we need in a dirt bike is much less of this unnecessary over engineering and a return to dirt bike simplicity. More parts means - more parts to break.**Our shop sees tons of bikes for broken gizmos.**Was Yamaha was just trying to impress us with their technology, rather than design a really innovative and practical engine? If so, all they got was complexity, not new technology. The formula car guys are experimenting with rotary drum valves that don't reciprocate at all, so there are no cams, valve springs, etc to adjust, wear out, or to limit the revs. That's a prime example of a simpler but more advanced system. I'm not advocating a return to the XT500, but sometimes I think that would be better than what we've got now. Look at the old 84 Husky 500 fourstroke. It used a twostroke bottom end, and it didn't even have an oil pump, but it ran hard and lasted forever. They ran the oil up the cam chain, and all the top end parts were roller or needle bearing mounted, so it didn't need much oil anyway. And I know there's a big debate about whether fourstroke carbs need accelerator pumps or not, but the roller-flat-slide carb on my YZ makes me nauseous. Honestly, if you were going to have all the 3D mapped ignition curves, wouldn't you be better off with fuel injection?

Fundamental rule number 3 states that if you're going to build a fourstroke, make sure it has a fourstroke powerband. As any YZ400 rider knows, if you don't keep it spinning it's going to stall, usually in the middle of a crowded turn or at the bottom of a hairy step-climb. I even ride twostrokes like they're fourstokes, using a high gear and lots of throttle opening, but the YZ400 is one fourstroke that must be ridden like a twostroke. It has very poor power down low, and it makes most of it's power up higher than God intended fourstrokes to be revved.**The key to acceleration is more about how much power you can put to the dirt, not how much peak power you can build. I've had the pleasure to ride a few factory built 250 supercross bikes, and they're the opposite of what you'd think. They were all bottom end and tractability, and as flat as Kansas on the top. They would have made the most fantastic trail machines ever because they were so easy to get traction and so fast out of the turns. This is more what I expect out of a fourstroke, and I'll absolutely guarantee you that built the right way, a fourstroke can rev no further than 7000 rpm and still accelerate faster than any twostroke on the track. If you look at the original Vertimati's, they had two and three speed gearboxes, and it's said that they only needed 1st and 2nd for starts; they could race they entire MX course in third, and they kicked ass on the twostrokes.**Just close you eyes and imagine THAT kind of wide tractable torque. It'd be fun, right? Not much like a YZ400, is it? I rest my case.

My point is this; Yes, I think the YZ is the best fourstroke on the market today, and it's not likely to be challenged anytime soon, even by the Cannondale (don't get me started on that!). But what we want is not an 11000-rpm street bike engine in a frame with long suspension and knobbies.**What we need from a four stroke is simplicity, lightweight, and tractability above all else. So while I'm out riding on my YZ, I'm still searching the heavens for another beam of light.


------------------
---------------------------------------------
Pete Denison
A-Loop Offroad, Inc.
“The Artists Formally Known as Moose Offroad” www.aloop.com
&lt;p align=right&gt;12-07-1999 :Edited<p align=right>12-07-1999 :Edited


Posted by: JonA---------------------

Very interesting and honest post.&nbsp;&nbsp;It's refreshing to see another rider questioning the Gods that be.&nbsp;&nbsp;I have ridden 2-strokes all my life and just recently decided to step it down a notch and buy a '00 XR400.&nbsp;&nbsp;Granted this is no rocket, nor intended to be to my knowledge, but I think the powerband is more like what you are describing.&nbsp;&nbsp;Compared to my RM250 it feels like, well a trail bike. But I took it on the track for the first time this weekend and if my lap times were any slower I would be surprised.&nbsp;&nbsp;Like you said, I put it in third and rode all day.&nbsp;&nbsp;No wheel spin, no mis-timed hits, no arm-pump, just a damn good time.&nbsp;&nbsp;I would hate to try and get a holeshot on this thing, but it would be a different story on a KTM520 I'm sure.&nbsp;&nbsp;I must admit I have never ridden a YZ400, but I did have one chase me for 5 laps and never get by.&nbsp;&nbsp;I think the Euro manufacters may use the YZ400 as a catalyst to take 4-strokes to the next level and then we will have a true dichotomy in motocross.&nbsp;&nbsp;Jon


Posted by: Jake---------------------

I gotta go with the weight issue!&nbsp;&nbsp;My WR is NOT a light bike.&nbsp;&nbsp;If you think about the physics involved, weight is critical to both MX and trails.&nbsp;&nbsp;The more weight moving forward, the harder it is to turn.&nbsp;&nbsp;Why was it Shane Watts was riding a KTM 125?&nbsp;&nbsp;I'm sure it had something to do with its ability to turn.&nbsp;&nbsp;The magazines are written by riders not physics majors (I doubt any even took physics!).&nbsp;&nbsp;They are always comparing horse power to weight.&nbsp;&nbsp;That's great for holeshots, but not for the turn!&nbsp;&nbsp;

Another FLAME on weight is that newer bikes are getting taller, moving their weight even higher.&nbsp;&nbsp;Granted, I sure like the 12" of travel, but this effort has its problems, too.&nbsp;&nbsp;I’m not even crazy about the camel backs.&nbsp;&nbsp;Once again, this moves weight higher.&nbsp;&nbsp;&nbsp;&nbsp;I like the factory Vermoti (sp?)&nbsp;&nbsp;I saw in one of the magazines that actually moved the gas lower on the frame.&nbsp;&nbsp;I think they moved the air box up front and the gas lower under the seat.&nbsp;&nbsp;I’d also like to see more tool packs and bags lower on the frame.

Any comments?

Jake



Posted by: Rich Rohrich---------------------

Interesting post Pete while you are entitled to your opinion your logic leaves a lot to be desired.

Point 1 - Weight. The YZ4 should be lighter, but given the expectations of the buying public it's unrealistic to use precious metals to decrease the weight, while increasing the costs. If you do,Yamaha (or anyone) ends up in the position where buyers start complaining about the cost (like the Cannondale naysayers). It's a balancing act that's tough to win, Yamaha struck a good balance. On the up side, if you spend time on the bike you find you can't feel the weight unless you are picking the bike up after a crash.&nbsp;&nbsp;Given the target audience they made the right choice.

Point 2 - You advocate simplicity and then suggest "rotary drum valves", a totally unproven technology with a monsterous price tag attached. Then you go on to use the "84 Husky 500 fourstroke" as an example of a simplistic design. I'll agree it's simple, it's also one of the most unreliable, under engineered abortions to ever roll on two-wheels. Kettering said it best "The price of progress is TROUBLE". Moving ahead requires some growing pains, just like Simons forks, and Fox Air shocks advanced to the excellent stock suspension we have today. We had XRs and loved them, we have the YZ4 and most of us feel we got our moneys worth, and the next generation should prove to be even better.

Point 3 - If you want a flat torque curve to ride around in the woods, pop one of your cool A-Loop kits on an XR and grin for hours. I for one applaud Yamaha for having the balls to build a real race motor instead of another warmed over trail bike. AS for not having any low end, you're doing something WAY wrong if you can't lug a YZ4 with a stock pipe, correct jetting, and the correct fuel. The masses are convinced that you have to put a pipe on every four-stroke, and clueless aftermarket companies guys are more than happy to build one, no matter how much it screws up the powerband. It's a versatile incredibly rideable motor in the hands of a C rider like me, and a serious weapon in the hands of someone who can really ride. People who expect it to be an XR will be disappointed, people who expect it to be a CR will be equally unhappy.

I'm no YZ4 zealot, but the simple fact is it's the best performance per dollar value in a four-stroke race bike (ubtil the new Honda and TM arrive) you can buy today. It's reliable, cheap, and fun.&nbsp;&nbsp;Anyone who believes that it will be better than a well developed two-stroke 250 is kidding themselves.


&nbsp;&nbsp;

------------------
Rich Rohrich
Applied Fluid Dynamics
rrohrich@interaccess.com
www.eric-gorr.com





Posted by: 380EXCman---------------------

Spelling "vertemati" (I almost bought one) TM is the one who is experimenting with the fuel tank airbox swap. Hey rich what is your first impressions of the new KTMs, with what has been written thus far.

------------------
More to follow im sure.....




Posted by: 380EXCman---------------------

Also I had a 98 DR350 that I put a big gun pipe and silencer on. It made a world of difference. Jetting it was an ordeal ended up I had to go 5 up on the main and 3 up on the pilot and I cut the top of the airbox off. It was like night and day . Sold the bike to my brother and he really likes it. Its not as "fast" (using the term loosely) as my 380 but for that matter a yz 400 is not either. What do you think about the big guns and is the performance gains more dramatic for say a dr350 than a yz400. I look at the yz's head pipe and silencer and it looks like it would be very useable. I rember my dr's stock pipe and it was about as big around as a quarter. just thought I would get your take on this.

------------------
More to follow im sure.....




Posted by: Rich Rohrich---------------------

I'm excited about what KTM is doing. They have always been able to build excellent four strokes, they just had the unfortunate habit of making them too tall and WAY TOO LONG for anyone but the dessert guys. Now that they have redone the engine and put it in an aggressive chassis from the two-stroke side of the house we should finally get to see what KTM is really capable of.&nbsp;&nbsp;a friend of mine is a KTM dealer who will also be selling Cannondales so I'm hoping to get a chance to take both of them apart sometime in the near future.

As for pipes, the old days of taking a stock pipe and increasing the ID and shortening the header are OVER. The new generation four strokes are designed as systems not parts lists. The aftermarket has done the YZ4 a great DISSERVICE by dumping all those oversize headers on the market. All they do for most people is punch a giant hole in the torque curve around 3500 and make the transitional jetting a NIGHTMARE in exchange for a bit of overrev. What these NITWIT companies don't seem to realize is the YZ4 has a short rod by Japanese standards and extremely small valve area (25.8%) to piston area ratio for an 11,000 rpm motor. Basically what this means is they biased the breathing towards the 3000-7000 range. Listen to Doug Dubach ride one sometime and you'll hear him short shifting compared to most guys. He knows!! The little overrev you get with oversize headers is lost on an engine that isn't designed to breath up there, and it hurts the powerband in a place where it can least tolerate it unless you're a flattracker, or riding Reno to Vegas . On 94mm big bore motors the oversize pipe is less of a liability because the extra bore size increases intake velocity enough to help mute the low rpm glitch.&nbsp;&nbsp;The Big Gun and the Yosh step headers have the most potential on a stock motor. I haven't had the opportunity to test them on the bike, but the dimensions look very good in a computer simulation . The stock pipe and muffler work very well, despite what MXA, DB, and the rest of the guys looking for advertising revenue will tell you. I'm building a 441cc SuperTT motor this winter, with a heavily modified cylinder head and I'll be testing a stepped pipe I designed based on the stock pipe. I'll be comparing it to the oversize single diameter headers just for fun (it easy to get one used CHEAP). The new Big Gun pipe will probably work better than either though :http://dirtrider-forum.com/forums/ubb/smile3.gif

Times are changing and that half-assed "Engineering" those guys try pass off won't cut it anymore. Companies like Big Gun who actually truly engineer a product are the wave of the future.

RANT MODE OFF (for now)



------------------
Rich Rohrich
Applied Fluid Dynamics
rrohrich@interaccess.com
www.eric-gorr.com





Posted by: Payday2---------------------

I have a few points to touch on....

1)&nbsp;&nbsp;The YZ4 is a great bike, BUT, it it very heavy.&nbsp;&nbsp;I can feel the difference anytime I'm on it, and I can really feel it if I jump on it right after I get off my RM.&nbsp;&nbsp;It seems Yamaha could do something about the weight of the bike without increasing the price too&nbsp;&nbsp;much.&nbsp;&nbsp;The first time I ever loaded Jason Clishe's 400 in my truck, I thought my nuts were going to sag to my knees.&nbsp;&nbsp;That bike is heavy!&nbsp;&nbsp;Yamaha's claimed weight is a joke of a number (238... bbwwwaaahahahahahahaha!!!).&nbsp;&nbsp;BUT, it does do most everything extremely well.&nbsp;&nbsp;Even after just a couple laps on Jason's bike, I could corner on it faster than I could on my RM.&nbsp;&nbsp;It takes a different riding style, but it corners good, flies like a rocketship, and is never searching for traction.&nbsp;&nbsp;The weigt of the bike would wear me out too quick to seriously think of racing one though.&nbsp;&nbsp;Come to think of it, it's heavy, but it also seems to carry it's weight too high for my tastes.&nbsp;&nbsp;YMMV.&nbsp;&nbsp;It also deos not want to lug down low without stalling.&nbsp;&nbsp;It seems like Yamaha would have been better off putting a little more flywheel on it, IMO.

2)&nbsp;&nbsp;We will never see another sub 200 pound 250 with a reasonable price tag, IMO.&nbsp;&nbsp;Today's riders are flying 6 times as far as the riders of the 70's.&nbsp;&nbsp;Bikes back then could be made lighter, because they were not as beefy, because they didn't have to withstand 120 foot triples and things like Larocco's Leap at Reb Bud.&nbsp;&nbsp;Bikes now are also liquid cooled, meaning more weight.&nbsp;&nbsp;We own a mid 70's Yamaha enduro, and I took at that thing and think "I wonder what would be left of it if it was ever jumped over a 120 foot triple?"&nbsp;&nbsp;Probably not much.&nbsp;&nbsp;&lt;G&gt;

3)&nbsp;&nbsp;I think as more manufacturers get involved in the 4 stroke market, you will see the weight come down, but never to a 2 stroke level.&nbsp;&nbsp;I'm excited to see what the KTM's are going to be like.&nbsp;&nbsp;As more poeple get involved, I think the envelope will be pushed, and the bikes will get better.

J&K

------------------

J&K Racing Since 1997
Keepin' it real!


Posted by: ATK ADAM---------------------

Well, I agree that the Yamaha is not the Holy Grail of 4 stroke technology.&nbsp;&nbsp;Hopefully the rest will improve on it and we'll have better and better bikes coming out in the future.&nbsp;&nbsp;I also agree that Yamaha screwed up by making the bike so complicated.&nbsp;&nbsp;For now I'll stick with my ATK that has a 20 year old motor with it's electric starter and weighing 300 lbs.&nbsp;&nbsp;You just can't jury rig an electronic carb with zip ties and duct tape when something goes wrong.


Posted by: Rich Rohrich---------------------

ATK Adam wrote :
Quote:
You just can't jury rig an electronic carb with zip ties and duct tape when something goes wrong.


Adam if everyone thought that way we'd all still be riding Hodaka Super Rats, and CL 350s http://dirtrider-forum.com/forums/ubb/smile2.gif




Posted by: Rich Rohrich---------------------

Payday2 wrote&nbsp;&nbsp;
Quote:
It also deos not want to lug down low without stalling.&nbsp;&nbsp;It seems like Yamaha would have been better off putting a little more flywheel on it, IMO.


John, my guess is Jason's bike isn't jetted right or he's using fuel that isn't cooperating. With the stock pipe it's pretty easy to lug the motor if it's setup correctly, but you're right all day lugging like woods guys do would do better with some extra flywheel weight. I really love the spin up on a SX type track so I'm happy with the way Yamaha did it.






------------------
Rich Rohrich
Applied Fluid Dynamics
rrohrich@interaccess.com
www.eric-gorr.com





Posted by: William---------------------

Hodaka Super Rats and CL 350, yuk.


Posted by: ATK ADAM---------------------

Rich,that's very profound.&nbsp;&nbsp;But we do have simple bikes available today that are quite a bit better than a Super Rat.

------------------
Adam
94 ATK 605
94 ATK 406
84 YZ 490


Posted by: duner---------------------

Quote:
But we do have simple bikes available today that are quite a bit better than a Super Rat
Like the Z50... I know, I learned on a Wombat (Combat?) and the '98 Z50 has superior power, handling, and over all comfort http://dirtrider-forum.com/forums/ubb/wink.gif. But nothing could beat that Hodaka style, no one can argue that! http://dirtrider-forum.com/forums/ubb/cowfrown.gif


Posted by: Warhawk---------------------

I jsut want to comment on the Big Gun pipes. I've got an XR650L that had the stock exhaust when I got it.&nbsp;&nbsp;First I opened the airbox, rejetted and went with a Thumper racing exhaust insert. Big improvement!&nbsp;&nbsp;Then I decided I needed a better pipe and bought a Barnum pipe, with a 4 inch suptrapp silencer.&nbsp;&nbsp;This used the stock headpipes and was as dramatic an improvement as all the other mods combined. But it was loud and I didn't like the supertrapp vented exhaust gas onto my rear fender. So when I saw a used Big Gun system for sale, I jumped on it. The Big Gun pipe really woke up the big XR, now third gear wheelies are easy and I wouldn't have believed the power increase.

I've also got a Big Gun on my XR250R, but all I can judge it against is the stock pipe.&nbsp;&nbsp;Again a HUGE power increase, not to mention great sound and great looks.


------------------
Jim Nelson - Douglass, Kansas
1989 Honda XR250R
1994 Honda XR650L
1976 Yamaha TT500C
1999 Honda Recon




Posted by: Rich Rohrich---------------------

Adam, my point was the Yamaha is extremly simple and easy to maintain. Anyone who can't maintain a YZ/WR 400 won't be able to maintain a late model two-stroke either, and frankly is probably too stupid to own a motorcycle in the first place.



------------------
Rich Rohrich
Applied Fluid Dynamics
rrohrich@interaccess.com
www.eric-gorr.com





Posted by: Vincent WR400F---------------------

Want an end to the stalling on a YZ? Get a WR 400... The heavier flywheel and lighting coil (magnetic field) keeps this bike from stalling easily at all. It can be stalled but not easily. Ive lugged my down in the woods to the point I was hangin off the back with my tongue draggin the seat but it kept plunking right along up the hill. Dropped it upside down a greasy log hidden in wet grass, there it sat idling happily upside down, picked it up (clutch in of course) and then rode it happily away. Point is, this bike is so many light years ahead of the other thumpers available there is no comparison. Ive ridden for 30 years now and owned lots of thumpers and Im telling you these bikes rip!&nbsp;&nbsp;


Posted by: semi old guy---------------------

The new Bergs are supposed to be about 20 lbs lighter than a YZ400


Posted by: Dirt Magnet---------------------

I think Rich is right! You CAN lug a YZ400. You can lug it out of your van, you can lug it around a track, you can lug it up on the bike stand, you can lug it up the ramp when you're done, and you can lug it back to the dealer when something with more bottom end power comes along!




Posted by: Shaltac---------------------

Didn't the AMA or some other sanctioning body make up the weight rules in the late 70's to help "even out" the competition when some manufacturer complained (I remember reading a story about that on www.all-offroad.com&nbsp;&nbsp;I think, was a while ago). Wasn't this why the bikes got heavier to begin with. Wasn't there a time when the 2 strokes were experimental tempermental beasts that were heavy and didn't perform, and 4 strokes ruled the world?
This is all before my time, but i remember old timers telling stories to that effect. Any one remember there history to set this straight?

------------------
Y2KDX here I come....





Posted by: Vincent WR400F---------------------

Gee there Dirt Magnet, sounds like a little thumper envy there to me. You must have been roosted by one at one time or another. hehehe


Posted by: tzracer49---------------------

First of all, I own both 2-stroks and 4-strokes. Both are fun in differsnt ways. As far as weight goes, they are all heavy! I just sold my Yamaha Tz250, a 250cc 2-stroke twin grand prix race bike. It weighed in with an empty fuel tank at 210lbs. And that was without all the trick Ti parts most racers have. Yes Yamaha could have made it lighter, but like it was said before, how much more would you be willing to pay. Everything has its price. I plan on buying a yz400 and one of the first things I plan on doing is putting a flywheel kit on it. I love lugging it and just having to crack the throtle to take off, rather than wring the s*%#@ out of it and play with the cluth. Basicly it is personal preference. ride what you like.
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Tzracer


Posted by: YZWrench---------------------

I'd have to agree with you 100% I. Thumpalot. I'm going from an RMX250 to a YZ426 and it is a learning and fun experiance. It actually feels lighter than the RMX did, and it seems the powerband and eng. braking make it easier to ride, except for stalling. Once I put on a steering stabilizer and adjusted the suspension it made a great high-speed desert sled and did well in the tight stuff also.

Phil
'00 YZ426
'00 XR100
'98 300EX


Posted by: YZWrench---------------------

Well, I'm a step ahead of you on the grease- I took just about the entire bike apart before I even rode it and found the frt wheel and steering bearings almost dry. After lots of waterproof grease and loctite the bike was ready. It was a good thing I took friends on my first ride because it took all of us to start that thing after a stall. I went 2 sizes leaner on the pilot and adjusted the ign. timing (it was right on the edge of the mark)and this made a huge difference, with only having problems twice (starting-wise) last weekend out of 3 days of riding. I'm definitely going for a flywheel wt. to curb the stalling. Thanks for the heads-up! http://dirtrider-forum.com/forums/ubb/smile.gif

Phil
'00 YZ426
'00 XR100
'96 300EX&lt;p align=right&gt;01-05-2000 :Edited<p align=right>01-05-2000 :Edited


Posted by: YZFPilot---------------------

Just took delivery of a 426f last week.... The bike is awsome, period....


Posted by: taraker---------------------

Who ticked off this guy at Yamaha, every other day this is re-posted so it can be moved to the top of the forum.




Posted by: Rich Rohrich---------------------

I pretty disappointed that Pete didn't bother to ever respond to anyone in this thread. He signs on to the board, posts an incredibly ill-conceived rant and then disappears. I was hoping we'd get some actual dialog on this subject.&nbsp;&nbsp;OH WELL http://dirtrider-forum.com/forums/ubb/smile2.gif



------------------
Rich Rohrich
Applied Fluid Dynamics
rich@dirtrider.net
www.eric-gorr.com




Posted by: A-Loop---------------------

Oops, sorry Rich. I've just been enjoying reading everyone's response to my post about the YZF. I guess I should have been more.....responsive. Anyway, I'm NOT pissed at Yamaha, quite the contrary. I'm really impressed at all the changes that they've made to the 426 this year. It's just that I'm of the opinion that we've got a long way to go before the 4-stroke reaches it's true potential. That's good news, right?

If you want discourse, wait to you hear my Cannondale Rumors! As soon as I can think of a tactful way to type 'em, i'll post 'em.

Seeya on the Trail!


Posted by: TexKDX---------------------

With only 60 miles on my WR (tuned to YZ specs - see&nbsp;&nbsp;"WR Myths and Truths" post) I have a decent handle on the supposed stalling "problem".&nbsp;&nbsp;It is pretty simple, just pull the clutch in and keep the throttle cracked in slow speed situations.&nbsp;&nbsp;But wait a minute, that is how I ride my 300EXC!?/&!

OK, high compression, short stroke, minimal flywheel weight equals a motor that does not chug like a long stroke, low compression, heavy flywheel motor.&nbsp;&nbsp;Glad I figured THAT ONE out.&nbsp;&nbsp;Hey, the bike still chugs pretty darned well off the cam.&nbsp;&nbsp;The power it tractible and the bike accelerates pretty well in this range.&nbsp;&nbsp;Yes, you have to clutch it a little more than an XR in really tight stuff.

But wait now, what happens when you give it the gas and fan the clutch?&nbsp;&nbsp;The motor wraps up like a 250 2 stroker with a light flywheel, and you do your best to keep the front end on the ground!&nbsp;&nbsp;The bike rockets forward and pulls like no other 4 stroker when on the cam.

All this in a YZ250 chassis, with say a few too may Big Macs in the old saddlebag of extra weight.

Hey, this is one fantastic motor and motorcycle.&nbsp;&nbsp;A step forward? you bet.&nbsp;&nbsp;One irony in all this is the reliability.&nbsp;&nbsp;Personally I did not expect this motor when it came out to be durable.&nbsp;&nbsp;But think about it - the Genesis 5 valve motor technology has been around since when, 1986?&nbsp;&nbsp;Yamaha had done 95% of the groundwork before the 400 was ever conceived, so execution was a relative snap.


Posted by: bud---------------------

Pete, how bout posting these cannondale rumors on the flame board? No tact required there http://dirtrider-forum.com/forums/ubb/smile.gif


Posted by: MX Tuner---------------------

Some good dialogue going on in this thread. But Pete, I'm a bit disappointed in your comments. It almost seems as though you're simply trying to start some sh!t. Certainly someone of your intelligence and familiar with the industry and bikes in general, knows the finer points of the poor argumants you bring up concerning the YZ/WR 400. No, it isn't the "perfect" 4 stroke but it's the best thing out there for the time being. It is very cost effective for a stock bike. Sure you can get lighter, but who wants to deal with a Husabergs quirks, reliability, resale value, parts availability, etc.

You complain about the complexity and then want the rotary valves F1 is experimenting with. You want basic but then want a CF con rod? I think you need to find a new crack dealer because you're getting some bad drugs. Sorry if I come off sounding like this is a personal attack (believe it or not, it isn't), but I'm scratching my head wondering because I know you are very familiar with both sides of the argument.


------------------
MX Tuner
mxtuner@mindspring.com




Posted by: A-Loop---------------------

Yes, I agree there is some great dialog here. I don't know what you mean about trying to start something, unless it was to start people thinking.

Let me restate my point. Here goes... If you ever rode an old Triumph single, if you ever rode an old Husky 510 single, if you ever rode an International Harvester Tractor, then that's the TYPE of powerband that I'm speaking of. To me, an ideal fourstroke powerband is totally flat, meaning that it makes nearly as much power at 1000 rpm as it does at 7000.
As revolutionary a bike as the YZ400 is, nobody can deny that it is a very peaky powerband, and in this area I contend that it resembles a two stroke rather than a four stroke.

As to complexity and weight, two negatives of any dirt bike, my point is that they go hand in hand sometimes, and that I welcome changes which reduce both.

Everybody is entitled to their opinions. I know that there is some smart guy right now reaching for his keyboard to tell me I should go back to the three machines listed above if I don't like the YZ, so let me state that I have owned the Triumph, the Husky and the International Harvester, and the International had the other two beat on handling and power, and lost only slightly in the suspension department. I LIKE YZ400's, I just want a fourstroke to purr like a fourstroke. 'Nuff said.
<p align=right>01-21-2000 :Edited


Posted by: BigBore---------------------

I'm with A-Loop on this one.&nbsp;&nbsp;The "rev to the moon" style of power just doesn't interest me.&nbsp;&nbsp;Again, this was a big factor in buying my 600...I don't have to rev the beans out of it, so in turn its gonna last a long, long time.&nbsp;&nbsp;

My friend has a YZ400, and I've ridden it quite a bit (in very tight singletrack, to mx-style grass track), to see what I'm "missing out on."&nbsp;&nbsp;Yes, it is a nice machine, but not for everybody.&nbsp;&nbsp;It felt like it wanted to stall too much in tight going (even with a 12oz flywheel weight)...I know thats just my riding style showing, though.&nbsp;&nbsp;Everytime I ride it, my friend tells me, "you need to rev it more, you're not revving it enough."&nbsp;&nbsp;And to my ears, its screaming, but I'm used to an engine that makes its peak power at aroud 6,000 RPM.&nbsp;&nbsp;About the only thing I liked about the YZ was the inverted fork (very quick and precise steering), and the thin, flat feel of the bike.&nbsp;&nbsp;

Again, I'm not saying its a bad bike, its a great bike.....just not great for everybody.&nbsp;&nbsp;http://dirtrider-forum.com/forums/ubb/smile.gif&nbsp;&nbsp;

------------------
BigBore
'99 XR600R
Yes, it's fast...no, you can't ride it!




Posted by: michigan---------------------

I must admit that I've never ridden a 400/426, but I DO know that I just bought a bike that is 30 pounds lighter, makes more low rpm torque, more high rpm power, and always starts on the first kick (even if it has just bounced ass over teakettle down a hill), and it doesn't hurt my ears.
Oh, and it was a grand cheaper than the yamaha four stoke.

Maybe it would be different if kawasaki sprinkled a little "technology" on it!


Posted by: SFO---------------------

super stale thread but in rereading it I am wondering something.
The triumph cub and the husky510 are nearly extinct.
I am curious % wise how many yzfs will be left when they are 20 years old, compared to a cub or a husky.
I personally like the light flywheel feel.
Who in there sober mind would call a aircooled husky 4st reliable?
I got a husaberg you might be interested in, early 90's vintage...


Posted by: Ol'89r---------------------

[QUOTE=Shaltac Wasn't there a time when the 2 strokes were experimental tempermental beasts that were heavy and didn't perform, and 4 strokes ruled the world?
This is all before my time, but i remember old timers telling stories to that effect. Any one remember there history to set this straight?
QUOTE]

Dayum. Who dug this one up, Bill??

Gonna have to fire up the way-back-machine for this one.

Shaltac.

When the 2 strokes first came out they were not very impressive. Materials for pistons, bearings, seals, rods, etc, etc, were substandard compared to what we have today. The chances of finishing a race on one without seizing a piston or fouling a plug was slim to none. You had to ride with one finger on the clutch lever so it didn't pitch you off when it seized. They were very hard to ride since they didn't have power valves to control the torque so, they were either 'off the pipe' or 'on the pipe'. Nothing in between. It was like toggle switch horsepower, not a smooth powerband. The ignition systems were not very good and didn't produce a hot enough spark to keep the plugs from fouling. That along with the lack of good 2 stroke oils. Most everyone used Blendzol, a bean oil that smelled like you were running fuel and made your eyes burn. With the expansion chambers they were very loud and during a race you would pass many of them while their riders were kicking, kicking, trying to start them. Sound familliar???

About the only thing they had going for them was they were lighter. Of course you made up for that by having to carry a pocket full of spark plugs and a plug wrench. Most everyone thought they were only a fad. Probably won't be around for long.

Well, thanks to technology and the advancement of materials, the two stroke has come into its own. High silicon pistons, special coatings for cylinders, power valves, electronic ignition systems, chrome moly, magnesium, titanium, blah, blah, They are now, state-of-the-art race bikes.

Four strokes are undergoing the same transition. By using lighter materials, better materials and modern electronics, the 4 strokes are now very close to the 2 strokes as far as the way they handle and the weight. Much of this technology has been around for many years. The difference is in the materials now available to us. The rotary cam valve has been around since the early 70's. There was a bike called a Zimmerman that used two hollow shafts that rotated and had the carburetors attached to the end of the shafts. This bike put out tremendous horsepower and reved to the moon. It was very successful in So California desert racing. The main drawback was the frame kept breaking and the bottom end could not hold up to the high rpms that the engine was capable of.

Most of the technology that we think of as new, has been around for many, many years. Monoshocks go back to the 20's. The difference today is the materials that are available.

It's funny how much advancement in technology we have seen just since this thread was first posted. I purchased a WR400 and thought it was the best motorcycle I had ever owned. Trail rode it and raced it and did pretty well on it. At least until the CRF 450's came out. The CRF's were so much faster and better than my WR, I couldn't believe it. Having won races on the WR, I couldn't even keep the CRF's in sight the following year.

Back in the day we took 450 lb street bikes and stripped them down, machined everything and ground every extra bit of metal away and made 370 lb racers out of them. Today you can walk into your local dealer and walk out with a bike that is very competitive. A lot of people complain about having to check their valves and maintain their bikes but, back then we literally had to build our racers from scratch.

I know what Pete is talking about in regard to the old thumpers torque. Having ridden and raced Triumphs for many years and owned and trail ridden XR's, I like the torque that the old long rod thumpers had. And yes, I even raced a Tigger cub on shorttrack. Still own several Triumph twins. And although that type of torque works very good on trail, it doesn't cut it on a track. Especially a mx track. For that reason I keep my XR for trail and have a CRF450 for racing.

But that was then and this is now. What we are seeing today is the resurrection of the four stroke. This is just the beginning, the best is yet to come. Everyone complains about the cost's of the new bikes, the electronics, the complexity. But that is what it takes to stay up with technology. We have some fantastic machines available to us today. Most all are very good. Two stroke, four stroke, red one's, blue one's, yellow one's, green one's, orange one's. Pick a color and go ride.

Oh, and btw Bill. I know where there are a couple of tigger cubs and they still run.

Ol'89r



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