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144 or 250f?
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Posted by: kxguy967---------------------

ive got a 2000 kx 125 right now that i feel wont compete with a newer 125 or 250f. i thought i had my mind made up with a 250f, but ive heard alot of stuff about used 4 strokes. would it be worth my time/money to get the 144?

Posted by: robwbright---------------------

IThe 144 is worth the money. People have different opinions as to whether they can compete on an equal level, and I'm going to refrain from starting another combative thread until I have some results this spring, but the difference between a near stock 125 and a modded 144 is amazing.

Look for my thread in the Forward Motion forum for more description of the power difference on my freshly minted Eric Gorr 144.

http://dirtrider.net/forums3/showthread.php?t=126800

I stayed 2 stroke for 2 primary reasons:

1: $$ - the 4 strokes are more expensive to run and maintain and REALLY expensive if you blow a motor- Plus I couldn't afford to buy a new bike.

2: I just like 2 strokes better overall - everything from ease of maintenance to the "hit" of the power.

Will a modded 144 take a modded 250f? No, mostly likely not. Will a modded 144 be competitive in the class. Yes, I think so based on my experience last year and what I've experienced so far with the 144.

If money is a concern, as it was with me, it was/is a no brainer as far as I'm concerned.

Regardless, it's 95% rider and 5% bike - you're going to beat almost all of the guys you're better than on the bike you have now - even if they are on a 250F. If they're about as good as you and beating you, the 144 might help. One particular guy at the local track was a big part of the reason I did the 144. I could run even with him on the 125, but I could never seem to get around. I'm hoping the 144 combined with some more practice and experience will get me by him . . .

Posted by: kxguy967---------------------

im so torn. now im totally unsure what i wanna do

and i have to consider the fact the bike is 6 yrs old now.

Posted by: robwbright---------------------

The good news is that I suppose that a 2000 144 motor with port and polish would be as fast or close to as fast as a 2006 144 port and polish. I'm not speaking from experience or knowledge here, and maybe I'm wrong about that, but it would seem that one could only go so far with 144cc, regardless of how old or new it is. Certainly, there are no stock or even mod 125s - even the KTM - running anywhere near 37-39 HP, which the 144s will do when properly jetted. Apparently most stock 250F's are in the 32-24 HP range - but of course they have a much broader powerband.

My father in law is doing very well thus far on the east coast karting circuit using a 1998 CR125 motor built by Boyesen.

However, there would/could be significant upgrades in suspension/handling/ergonomics, etc . . .

I guess it just comes down to whether you have around $500.00 or $5000.00. I had $500.00.

If you look a little over halfway down the page on the below link at a post by marcusgunby- post #66 - you'll see a comparison dyno between an 04 RM 125 and an Eric Gorr 2001 CR 134. There is no comparison, as you'll see.

http://www.dirtrider.net/forums3/sh...&highlight=250f

Posted by: Chili---------------------

Quote:

Originally Posted by kxguy967

but ive heard alot of stuff about used 4 strokes.

This line catches my attention, are you planning to buy a used 4 stroke? If that is the case my vote is for the 144, since I would never buy or advise anyone to buy a used 250F. If you're looking at a new 250F get the 4 stroke.

Posted by: kxguy967---------------------

unless i win the lottery, im buying used. whats the deal with used 250fs, cuz ive seen lots of 02s and 03s go for around 2700. so after ( if ) i sell my bike, i should need about 800$ the 144 is like 500 or 600$ right? dollar for dollar, is the 144 on my 2000kx 125 gonna be better for me than a used 250f? i know rebuilds are super expensive on 4ts.

Posted by: robwbright---------------------

From what I know, if you want to buy a used 250F, you better make sure the guy knew how to do maintenance and did it regularly. If not, you don't know what you've got. . .

Not knowing what you've got on a 2 stroke might cost you $400 to fix. Not knowing what you've got on a 4 stroke could cost $2000 to fix.

At this point in my financial life, if I blew a 4 stroke motor I'd be parting out the bike and probably unable to buy another.

Posted by: Chili---------------------

Quote:

Originally Posted by kxguy967

is the 144 on my 2000kx 125 gonna be better for me than a used 250f?.

No, but buying someone elses timebomb won't be good for you either. Unless you know the 4 stroke owner and his maintenance records thoroughly you are just asking for heartbreak with a used 4 stroke, Especially if you are considering anything other than a Yamaha 250F.

Posted by: HajiWasAPunk---------------------

Rowbright, where did you find the HP numbers for the bikes? I've been wondering myself what those numbers were but couldn't find it anywhere?

Posted by: kxguy967---------------------

lets see if ive got everything straight. a 144 kit will help my bike, but still would have some disadvantage from the 4t. the main reason i want the 250f is cuz i want low end power, which my bike has NONE of. and unless i know the owner or know about the regular maintenance records, a 250f will be no good. has anyone ridden both and could tell me if a 144 has a descent amount more torque than my 125?

Posted by: Chili---------------------

Quote:

Originally Posted by kxguy967

unless i know the owner or know about the regular maintenance records, a 250f will be no good.

Sorry if I gave you the impression that ALL used 250F's will be bad, that is not the case. The penalty however for getting one that has been poorly maintained can be extremely harsh on a wallet, thus I would never take the chance on a used 250F.

Posted by: kxguy967---------------------

so are the risks really that much greater buyin a used 250f but if something is wrong itll cost me, right? i really want a 4t but not if its gonna be unreliable.

Posted by: robwbright---------------------

HP numbers are scattered all over this website. Search for "Dyno" or "Dyno Chart" or "Dyno graph" and theres a thread about 15 pages long with various charts. There are other charts posted on other threads as well.

The problem is that every dyno reads a little different, and everything from temp to humidity affects the reading.

The best 144 dyno I've heard of was 39.5 or so HP.

The 144 will have more torque than the 125. My RM has a MUCH stronger midrange to top end. No clutch work needed to pull the front wheel off the ground in 1st to 3rd on the street in front of my house. There is a small improvement in low end, but nothing to get worked up about. If you look at that dyno I referred to before, you can see the increase - from say 7000 rpm to 12000 there is a 15-25% increase in HP. No small bore, 125 or 144 will have any significant amount of low end torque, tho. There's just not enough displacement there, and they're designed to rev, not pull. I think the dynos will show that new stock 250 2T's run in the 42-46 HP range. A 38 HP 125/144 is pretty impressive since it weighs 20+ pounds less. . .

One of the fellows posted a thread recently (masterphil, I think, in which he had calculated the cost of running a 2T 125vs. a 4T 250F. The approx $$ amounts were $10/hr for the 2T and $20/hr for the 4T. This was using expert rider top end changes for the 2 stroke and waiting twice as long as yamaha recommends for doing the top end on the 4 stroke. (i.e. 5 hours for rings and 10 hours for piston on 2T . . . I'm not sure on the 4T.). The calculations DID NOT take into account the difference in cost of rebuilding a blown motor.

Many 4T guys recommend changing the tranny oil EVERY RIDE.

kxguy967 - If money is a problem, it would appear that you need to learn to ride the 2 stroke better.

LOL

By the way, I somewhat disagree that the 144 won't be better than a used stock 250F - IF YOU CAN KEEP A 2T ON THE PIPE.

The 250F stock or otherwise will definitely still be easier to ride. However, I had ridden a dirt bike about 4 total hours in the 15 years prior to May 2005 and had never been on a real MX track prior to my first practice and then race in late June.

I placed above 250F's in every race (C and D class) on a basically stock 125. I anticipate that an extra 8 HP of the 144(after switch to race fuel) will put me ahead of more of them as well. Of course, even though I didn't race it, I grew up on a 1986 CR80, so I'm used to the 2 stroke power spread . . .

While short on torque, the 144 will show approx 6-7 more peak HP than most stock 250F's and it is lighter and feels considerably lighter when cornering. Thus, if you can ride it well, it should be more than competitive with the stock 250f's.

As noted, a modded 250F is another story altogether. . .

Posted by: kxguy967---------------------

all i ride and all ive ever ridden were two strokes. i know how to work the clutch and keep it in the power. the only real reason im intersted in 4 stroke is cuz everyone i talk to says after goin 4 stroke they'd never even consider another two smoker. i guess im more curious than anything. i love my 125 to death, just dont like the fact that it has no low end. unless i find an AMAZING deal on a 250f, it looks like im goin 144 big bore kit. wheres the cheapest place to look?

Posted by: i_955---------------------

If money is a concern a 250 4 stroke might not be the bike for you.

Read this.

http://www.dirtrider.net/forums3/sh...ad.php?t=115201

If your looking for 250 4 stroke torque, more top end, cheap operating costs and light weight, then you can't go wrong with a 250 two stroke. There are a cazillion great deals on used 250 2 strokes in excellent condition. Most fun you can have on 2 wheels.

But a 144cc engine with the best suspension you can afford would be a good route.

Posted by: kxguy967---------------------

im deffinately not ready to jump up a class. im pretty sure im gonna do the big bore kit. ill probably have it ported too for a lower hit. unless i find a 250f for like 2200 or so im not gonna be able to afford it.where did u get yours done robwbright?

Posted by: kxguy967---------------------

i just checked out eric gorr's site. 475 for the bore piston rings porting, everything. has anyone else had work done by him? from what ive seen, 475 looks very reasonable, especially since it comes with everything plus porting.

Posted by: robwbright---------------------

Quote:

Originally Posted by kxguy967

all i ride and all ive ever ridden were two strokes. i know how to work the clutch and keep it in the power. the only real reason im intersted in 4 stroke is cuz everyone i talk to says after goin 4 stroke they'd never even consider another two smoker. i guess im more curious than anything. i love my 125 to death, just dont like the fact that it has no low end. unless i find an AMAZING deal on a 250f, it looks like im goin 144 big bore kit. wheres the cheapest place to look?

You need to look around here a bit more - There's a LOT of guys coming back from the dark side

to ride 2 strokes again. ost guys who are coming back say the 2 strokes are just more fun. If you look at the 2 stroke or 4 stroke poll, you may be surprised at the results.

As far as I've READ on here and from my personal experience, Eric Gorr is the ONLY way to go. He's about 1/2 the price of Rick Peterson Motorsports (RPM) and some of the other big name shops. He's been doing this kind of work for 30 years or so and has done over 40,000 cylinders.

You can call him anytime from like 10AM to 8 PM or something - if you can get him - he's a busy man. Can be easier to get him on the weekend. Nice guy, easy to work with, free shipping back to you if you prepay. He'll do exactly what you want. He received my motor UPS on a Tusday and I had it back on the following Thursday. However, it's a busier time of year now. . .

As to other shops, look at the following thread for a comparison of Eric's work vs. RPM's work on identical bikes. . .

http://www.dirtrider.net/forums3/showthread.php?t=30485

Posted by: robwbright---------------------

kxguy:

My comment about your needing to learn to ride the 2T better was not intended to be any statement about your riding ability - just that it's more difficult to ride the 2T as fast as the 4T. It can be done, even without a 144 kit - i.e. witness Bubba Stewart on a 125 against the 250F's in 2004 - but you'll have to work harder on the 2T and being a better rider doesn't hurt either. The 4T is kindof like cheating when compared to the 2T -don't have to use the clutch as much, more low end torque, wider powerband. But, it doesn't have the

factor of the 2T. . . About 50-75% of my riding is outside of racing anyway.

Note the Eric Goorr, Forward Motion slogan

"95% rider, 5% bike." By all means, though, make that 5% count!

Call Eric and talk to him! I'm sure he's done 50 cylinders like yours. . . he'll answer every question you could ask, and then some.

By the way, that link I referred to was about 2 '99 kx125's. The results should be comparable to what you would get with Eric's work since the 99 and 2000 kx125's were very similar.

Posted by: robwbright---------------------

kxguy:

Just in case you didn't actually look at it, here was my 1st ride report from the other forum:

First Ride Report - Eric Gorr Rm 144 (Jetting Fixed)

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

As noted in the other post, I had Eric do an RM 144, mo betta porting, race gas. No race gas on hand as my supplier has been slow to get it to me (off season). Thus, I stayed with 100LL AVGAS with the jetting slightly richer.

I had been running 11/52 gearing on the stock motor for more low/mid because the track I race most often is VERY short and tight. I recalled seeing a post about a 144 here where the rider stated that he was initially disappointed with the top end performance of his 144 until he change the gearing. So . . .

Prior to the first real ride on the 144 I changed the front sprocket so that I was running 12/52. I know it doesn't give a 1:1 comparison, but I didn't think I would need the 11 tooth anymore.

I was right. First run down the street, front wheel was off the ground in 1st, 2nd and 3rd at maybe 2/3 throttle. The upper mid range and top end are awesome compared to stock. The 144 revs and revs, on and on. It reminded me of being on my first 2 stroke - brand new 1986 CR 80 - when I was a 95 pound 13 year old

Even with raising a tooth on the front sprocket, the power hits significantly harder and earlier, the mid range is at least 15-20% stronger and the top end is amazing. The stock motor seemed slower on top than my dads 94 CR125, even when I was running 12/49. Between the motor and the sprocket change, I would estimate top speed is 15 mph higher. I can't imagine what the mid-top porting would be like.

I rode the bike out to the local strip mine for a little off roading. Gravel road for about a mile to get there. My rear tire is about 1/3 worn and needs to be replaced. Anyway, everytime I rolled on the throttle I got rear wheel spin. If I really got on it, the rear wheel would spin and kick out in all gears through 5th. This was NOT the case with the stock motor.

The strip mine was very muddy in most places. There is a 250 yard long, quite steep hill, out of a low area in the strip mine. I climbed it a gear higher on the new motor even with the sprocket change.

I tried a couple starts on the firmest ground I could find (grass covered). Mostly wheel spin through 3rd gear. Its going to take some practice and a new tire to take advantage of the power on starts.

My dad (1994 CR125) took one ride up the street. He was surprised by the change and commented that his CR wouldn't wheelie in 3rd at all. Dad is notoriously "frugal" and thinks $185 for porting is quite expensive. He said that I definitely got my monies worth.

My bro (2000 KX250) took the RM to the strip mines for 20 minutes. When he got back he said, "Man, it's definitely quicker than before." He also commented on the wheelspin.

Mom was inside when we were running up the street. She came out after 3 runs and said with some concern for my well being, "That thing sounds mean."

Note that all these results are with still imperfect jetting and AVGAS. I will report again when I get the race gas (distributor tells me it will be this week) and get it dialed in.

Conclusion:

The 144 kit is definitely worth the money. Other than wheelspin on soft or gravelly terrain (with an admittedly worn rear tire), it's much easier to keep on the pipe and revs out forever. The prior reports here are accurate - the 144 rips.

Eric's work is exceptional and his customer service great. I sent the motor UPS on Monday, and had it back a week and a half later on Thursday - even with Christmas over that weekend. I called him when I got the motor and he answered all my questions on the spot. I will definitely be sending my motors to him till he quits doing it or triples his prices.

Rob

Posted by: MOTOX888---------------------

I rode a friends 144 and 250f, personally, i would rather have the 144. It has got better bottom end power that my 125, and with the 144 you could rev that thing to the moon!! The 250f still has more bottom end, but if you know how to work the clutch in the corners you should have no problems and be extremely happy with the 144. You could also get more bottom end with the FMF shorty silencer, or the PC r304 silencer...those make a pretty noticable difference.
After riding that 144 id say it has a lot more tourque than the 125, and i would say it is well worth the money!!!

Posted by: kxguy967---------------------

looks im givin eric a call! now im really excited. ive only had the bike for about a year and a half and im already bored with its power. ive already got a procircuit works pipe, and im gonna get an r304 shorty silencer. i geared it down one tooth in the front, and ill probably keep it that way just so i can have a heads up comparison, and maybe switch it back in the future. im gonna have it ported for low to mid cuz thats all i really want. thanks for all the advice, i may of made a mistake without ya.

Posted by: MOTOX888---------------------

Have fun!!!!!!!!!!!!!

Posted by: Chili---------------------

Quote:

Originally Posted by MOTOX888

and with the 144 you could rev that thing to the moon!!

That's a direct contrast to every post I've ever seen about the one downside to a 144, losing top end overrev.

Posted by: robwbright---------------------

Quote:

Originally Posted by Chili

That's a direct contrast to every post I've ever seen about the one downside to a 144, losing top end overrev.

Not true - I believe Eric's more recent 144 pistons are lighter than before. Anyway, my bike revs much better now than stock and I saw another recent post from a 144 owner saying the same thing. . .

Posted by: robwbright---------------------

Quote:

Originally Posted by kxguy967

looks im givin eric a call! now im really excited. ive only had the bike for about a year and a half and im already bored with its power. ive already got a procircuit works pipe, and im gonna get an r304 shorty silencer. i geared it down one tooth in the front, and ill probably keep it that way just so i can have a heads up comparison, and maybe switch it back in the future. im gonna have it ported for low to mid cuz thats all i really want. thanks for all the advice, i may of made a mistake without ya.

From what I've read, low mid is not recommended for 125's because you will not gain much more in the low end than you would with mo betta. Mo betta is apparently the best (unless you're an expert and can handle mid-top) because you get an increase everywhere. However, talk to Eric about it - he'll know for sure.

Posted by: kxguy967---------------------

i was thinkin about gettin the mo betta, does it just give an equal upgrade or is there any range thats signifigantly better?

Posted by: robwbright---------------------

kxguy:

mo betta everywhere basically gives more power everywhere with the 144 - lets say +20% everywhere. However, since there is significantly less power at 4000rpm than there is at 11000rpm, the gain will not seem as substantial at the bottom. i.e. Theoretically, if you have 10 HP @ 7000RPM, then after the 144 and porting you'll have about 12 HP. If you have 30 HP @ 11000 RPM, then you'll have about 36 HP after the work. I expect you'll notice the difference . . .

According to Eric Gorr's Motocross and Off Road Performance Handbook re: KX125, 1998-2000 (the below is a quote of about 1/2 of the info in his book about the 98-00 kx125. As you can see, he knows what he's doing):

"FLAWS: too high compression, exhaust valve sticks open
FIXES: head mods, pro-circuit valve cover, stiffer springs

Although it has some minor problems, the 1998 model is a significant improvement over the previous generation. The 1998 model started with problems such as being sluggish and sprung soft, but by the time the 2000 model was released, the magazines were praising it as best bike in class. . .

The compression ratio on the 1998 and 1999 models is good for typical MX or enduro engine, but makes the powerband run flat at high rpm. Modifying the head for greater chamber volume will improve the top end power but reduce the low end power. Normally, I narrow the squish band by 2mm on a lathe by setting the tool angle to 22 degrees and cutting into the bowl. Afterward, polish the head with medium grit sandpaper to remove the tool marks.

With the 1998 cylinders, tuners tried all sorts of things, including lowering the transfers by turning down the cylinder base, widening the exhaust port, narrowing the exhaust bridge, and even grinding the exhaust valve cavity deeper near the bore so the flapper valve would open the port completely. On the 2000, Kaw seems to have gotten the porting right. They dropped the transfer ports and raised the exhaust port. If you're looking for more low end power, you can have the cylinder turned down 0.75mm and the head's squish band machined for a 1-mm recess. For more top end power, just experiment with layering base gaskets."

Rob

Posted by: robwbright---------------------

TALK TO ERIC!!

I've learned most of this from him and other guys here, and I'm prone to mistakes . . . He's not.

Posted by: kxguy967---------------------

yea it really does sound like he knows what hes talkin about. im gonna give him a call sometime this week. i cant wait.

Posted by: robwbright---------------------

kxguy:

I was testing my 144 with race fuel on Saturday - it was still really wet outside and hard to get the rear wheel to hook up.

However, I was practicing starts - up over the front end and gettin on it in 2nd, 3rd, 4th.

At one point the rear wheel hooked up right as I hit 3rd. The front wheel pulled off the ground about a foot and stayed there for 30 feet or so till I went to 4th. That was pretty cool

Another time it came up so fast I let off because I thought I might lose it off the back.

Definitely cool, especially given how damp it was everywhere. The only way I could really do anything was to stay on the dirt road (bit of gravel on it but still wet).

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144 or 250f?

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