Got it apart; the damage...

[IcutMetl]

Well, I took the top end off my 'wheeler. The bore looked relatively decent, with some crosshatch still visible, but no noticable scars or damage. The piston appears to be a Wiseco, I measured it at 66.25. It had some pretty decent scarring/galling on the exhaust side of the piston, the 'front, right' area; otherwise, the piston looked good. I measured the bore with a pair of nice digital calilpers at 66.50. That seems like an awful lot of clearance between the piston and bore, no???? I thought there was only supposed to be approx. .005" with a forged piston. The compression was 155-160psi before teardown. It would still start cold within 3 cranks and warm on 1 crank. Ran ok, but something was 'missing,' and it seemed to have a bit more vibes than usual.

I'm not sure how many hours were on it before I bought it, but I'm not even thru my 2nd full tank of gas. Supposedly it has always been ran on Golden Spectro and 93/94 octane at their 52:1 reccomended ratio. Jetting seemed to be pretty well on to me; there wasn't a ton of carbon buildup on the inside of the pipe, in the dome, or on top of the piston. Some, but not a lot I would say. The spark plug was a dark gray & not gummy or fouled, but I didn't do a true plug test either. There was some residual oil on the crank area, rod, underside of the piston, but it wasn't dripping by any means. I think when I get my cylinder worked and re-installed, I'm going to try a 40:1 mix of Super Techniplate instead.

What is your guys' take??

[IcutMetl]

Another shot

[IcutMetl]

And another

[Honda 250r 001]

hmm what happened there? have'er a bit to lean? im thinkin you need to run a 32:1 mix and jet a bit fatter. How long did you break the cylinder in for?

[IcutMetl]

Naa, I bought it like that a little over a month ago. Probably wouldn't even have the motor apart right now if I didnt' get some water up into the carb out riding one day; it didn't take much to make it run like crap; I'm not sure if that's what caused that scuffing though. I probably will run it richer when it gets rebuilt though.

[trx250rider]

if your bore is a 66.50 then you need to order a 66.50 piston..the piston from wiseco comes machined with the clearence already so it is actually a bit smaller then 66.50..if your piston is a 66.25 then its the wrong one..bring the cylinder and piston to machine shop and have them put real mics on it to get a true reading..the digital calipers suck

[Honda 250r 001]

Originally posted by IcutMetl
Naa, I bought it like that a little over a month ago. Probably wouldn't even have the motor apart right now if I didnt' get some water up into the carb out riding one day; it didn't take much to make it run like crap; I'm not sure if that's what caused that scuffing though. I probably will run it richer when it gets rebuilt though.

man you have to get a lot of water inside a motor to get the piston to look like that. You just dont go though a water puddle once and you loose 30 pounds of compression.

[05LSR250R]

Looks like it ran lean! Water doesn't effect the exhaust side.
Hell......it would take a lot of water just to make the intake look close to the exhaust side like that!

[IcutMetl]

I AM a machinist; journeyman card, degree, welding cert, spent a year doing field service for a global top 3 CNC builder, and now application engineer / sales for a global leader cutting tool maker. I don't have a dial bore gage or a mic big enough to read my snap gages here, and it's not important enough to put on a CMM. Digital calipers are close enough to get an idea right now.

Anyways, I would agree that it was running a bit lean. From what I've read on here about guys who've got their jetting done right and running a good mixture ratio, I didn't see that much residual oil on the rod, crank, or underside of the piston. The bike seemed to run pretty damn well; warmed up good, idled fine, and started very easily. I don't know exactly what caused the galling or how long it's even been there. I do know that when I rode thru the mud water spot on this trail and splashed the filter, it made me regret having an open air filter even with outerwears, it ran like **** for the ride back to the house and just didn't feel the same. Weather that caused it or not, I'm not sure, but it couldn't have helped it any.

I'm mechanically sound, but not a 2 stroke guru yet; that's why I come here to get your guys' advise. I'm going to order a piston kit, and send it out to have it match bored, honed, and light midrange port job.

[Honda 250r 001]

sounds like your on the right track. Stay away from that water though. haha