Tuning Help: 1997 yz250 w/pro-circuit platinum pipe

[yamasaki]

hi all,

i have a 1997 yz250 with a pro-circuit platinum pipe and shorty silencer on it. i havent opened up the carb yet, so i dont know what jetting is in there, and i couldnt find any charts on pro-circuits site with recommendations either.

the bike feels like its got no bottom end at all.. i have to clutch it alot and my confidence on the bike is really suffering and slowing me down, like when coming around a corner with a double right after it, i dont feel i pick up speed enough quickly, and i roll it..

my friend has a 98 rm250 and that thing just feels SOOOO much smoother than my engine.. it pulls no matter what RPM you're at. although the RM250 may really be a better motor, i have to think my bike just must be runnign like crap or something.

I live in Ft. Lauderdale, FL, sea-level. any recommendations on jetting/things to check? i even put on a shorty silencer and it made a small difference, but i need more bottom end. my bike feels like i have either zero power, or in an instant i have too much power.. somethings not right.

thanks in advance,

edwin

 

[oldfrt613]

Check FMF or Boyeson web sites for a starting point, or just call Pro Circuit. You didn't indicate if you had a fresh top end or if you have ever replaced your crank seals. Make sure your motor is in good shape or no mater what pipe you use, you'll be disapointed.

 

[yamasaki]

I called pro-circuit yesterday and got the jetting specs for my bike @ sea-level with their pipe. For anyone else's reference:

Stock pilot
Stock main
Clip on 2nd position from top of needle

I took my carb apart and cleaned it thoroughly, disassembled, cleaned, and reassembled my PV, and i pulled my exhaust off so i could at least peek inside my cylinders.

The top 1/4 (sides, not top) of my piston looked a little dark/oily and the rest of the piston looked nice and clean. however, my cylinder did look like their were some signs of a mild seizure i think. i saw some streaks along the cylinder walls. I'm not a cylinder expert enough to know whether the streaks are regular wear and tear and its time for a rehone or bore to next size, or if it was truly a mild seizure.

Anyways, i think the only place i have left to go is to put in a new top end if the carb/pv maintenance doesnt help. i cant imagine i'd have to jet down from stock with an aftermarket pipe on there, and i dont want to take that chance.

so, i'm gonna try closing my mixture screw another half turn and see where that gets me.

 

[yamasaki]

after re-reading my own post, sounds like i'm getting blow-by on the piston? that would explain the oil on the sides??

anyone got any input/feedback?

thanks again

 

[Rcannon]

I have the same bike. My friend also has a 98 RM 250.

The pro circuit pipe sucks on the 97 yz. I have one. It adds midrange power and a little top. It kills low end. Check **e-gay for a Noleen pipe. It works well on the 97-98 yz's. I have many others, but th eNoleen is the best.

As far as jetting goes, I would try a 165 or 168 main. I believe the bike came with a 170.

I have a stone-stock cylinder as well as a ported cylinder and milled head. Neither combination is a match in low end for the 98 RM 250. That bike has a lot of torque and is easy to ride. However, the YZ will run away from the RM in midrange to top end. After a while the RM gets booring.

The best engine mod I did on my yz is add a flywheel weight. This made the bike much easier to ride. I bought a set of weights, but would have been extremely happy with the 13 oz model.

The 98 ignition (black box) will plug right into your bike. I paid 20.00 for one on e-gay. This adds low and midrange power, but the bike will lose some top end. The bike is much more fun to ride with the 98 ignition.

My bike also likes short silencers. The shorter the better. The best one I have used so far is a stock model cut down to 6 inches total length. Oddly enough, the bike is not much louder.

Be sure and check your reeds. The stock reeds fray and chip. This kills low end power.

Even with a fresh top end, I never did like my Pro Circuit pipe.

 

[yamasaki]

Ok, so after another dud day at the track, i figured it was time to take a good look at the top-end.. sure enough, i think we have a problem here! take a look at my piston and cylinder pics below.

I guess its time for an overbore? Any advice/input? It looks like a small chunk of my exhaust port on the PV is missing too? Rings on the piston have no obvious signs of damage tho..

<a href="http://www.edwinrivera.com/yz250/rebuild/piston1.jpg">Piston 1 Link</a>
<a href="http://www.edwinrivera.com/yz250/rebuild/piston2.jpg">Piston 2 Link</a>
<a href="http://www.edwinrivera.com/yz250/rebuild/cylinder1.jpg">Cylinder 1 Link</a>
<a href="http://www.edwinrivera.com/yz250/rebuild/cylinder2.jpg">Cylinder 2 Link</a>

 

[yamasaki]

one more pic of the crown

<a href="http://www.edwinrivera.com/yz250/rebuild/piston-crown.jpg">Piston Crown Link</a>

 

[rosscopeeko]

I had a 91 kx125 back in the day and my piston looked the same as that. After finding out what the problem was i was told that the plating on the cylinder had worn off and i needed a replate which was going to cost a few bucks. I just put in a new piston, rode it a few times and it fried another piston. Hope this isn't the case for you. Take your cylinder in and have it checked.

 

[yamasaki]

yeah, that makes sense. cylinder does look like whatever "coating" is on it has rubbed off in that spot, which is where i'm getting the blowby causing the nastiness on the piston.

anyone got a cylinder for a 97 yz250 laying around? :(

 

[yamasaki]

ok, so i spoke with Millenium Technologies and I think i'm just going to do a core/exchange for $199. They send you a cylinder for $299 ($199 + $100 core). when you get the cylinder, you put yours in the box and send it back. when they recieve/verify your cyl is a usable core, they refund $100 back to ya.

quick & painless. i love it.

sending your cylinder in for a replate runs anywhere from $175 - $235 depending on the condition of the cyl. the core/exchange thing is just more of a "convenience". i read on their site they have "thousands" of cylinders in stock on the shelves. they have a picture of it too. pretty sick! sure enough, they had one of mine in stock.

 

[WWR]

The PC pipe sucks. Mine cut low end and top end, but would match the stocker in the middle. The stock pipe is actually alot better.

The stock reeds suck also. I went with a V-Force II, which really opened up more RPM's on top.

I would send your cylinder off to Eric Gorr. Heck, if it were me, I would have him turn it into a bigbore! Looks like someone may have made the mistake of attempting to port the stock cylinder and raise the exhuast port a tad. This cylinder is prone to having the plating peel off if you attempt that.

This bike also has some port tuning issues that can be remedied if you go with the overbore. Port work is included with the overbore. Go with the overbore, have it ported for 'Mo better everywhere', and it should eat your friends RM... ;)

 

[Rcannon]

Make sure your powervalve does not contact the piston when it closes. Try this link and view the "cylinder head" from the 98 yz 250. I know your is a 97, but the 98 diagram is easier to read.

Part 19, a "holder" wears where the powervalve, part 9, contacts it. The powervalve closes too far and rubs against the piston. You can either replace the parts or grind a small amount off of the powervalve .

199.00 sounds like a resonable price on the cylinder. The aftermarket coating is supposed to be better than stock anyway.

 

[yamasaki]

thanks for the info Rcannon. I agree on the price/quality. The cylinder also comes with a LIFETIME warranty on the plating. The guy I spoke with (Kurt) was also really helpful, returned my phone calls, ..etc. Excellent customer service and they shipped out my cylinder the same day i placed the order. so far so good.