My new 01 RM250...crapola....

[Micahdawg]

I've come to the conclusion that my head was milled since I found numbers etched in a spot that say "25". And I'm confident that this bike will not run on 93 octane gas without detonating. So my knocking, irratic idle, wierd power delivery down low I'm sure was detonation.

Last night I did a compression test and it pulled 200. Was hoping for something rediculous, but 200 didn't seem too abnormal for 93 octane. So I popped the cylinder head off and found a piece of the piston is gone.

This is a brand new Wiseco Pro-Lite. I've put about 3 hours of riding on it while it was acting up. The missing piece is on the exhaust side, top edge right above the ring. It started peeling back along the ridge, but only 1/3 of what loosened up was completely gone. Looks like the chipped piece of piston passed right out the exhaust. I don't see any marks on the exhaust valve or the cylinder so it looks like I've gotten pretty lucky.

The cylinder head has ZERO pitting, the very middle-to exhaust valve side of the piston top has some very slight pitting which I guess is evidence of detonation. The top side of the rings and piston are a little dark looking (kinda blued) which I guess is evidence of high temperatures.

So.....I'll be ordering yet another piston. Probably the same thing. This piston was flat top design, but I think the part number cooresponds with the "Pro-Lite". Does this sound right?

Also, i noticed the governor rod actuator was loose. It was connected to something inside the case, but moved up and down very freely. Is this right? Seems like it should not be able to move up and down as freely as it does.

Micah

 

[RM_guy]

I though that might have been your problem. If you really want to run pump gas you can have Eric redo the head. Detonation will definitely cause trouble and you're lucky the breakage wasn't worse than it was.

That bike does use a flat top piston. The ProLite piston is just their name for the lighter piston. I use them all the time.

The PV governor rod will more freely when the motor isn't running. Nothing to worry about.

Good luck.

 

[Micahdawg]

Any idea on the price difference of a stock head from Suzuki vs. Eric modifying this one. I could really care less about the 1 or 2 HP that someone got from this head mod. Ain't worth it if you have to run race fuel.

Micah

 

[RM_guy]

No idea but I gotta believe it's cheaper to machime it than buy new...maybe a used one? You may want to have Eric go over the cylinder and head to make sure evrything works OK together. I'd check with him.

 

[Studboy]

It is about $35 for head modifications and usually way over $100 for a head.

 

[Faded]

It is about $35 for head modifications and usually way over $100 for a head.

A new head for my bike is a whopping $56. :yikes:

 

[Studboy]

Yeah, Honda has to give CR owners at least some sort of a good feeling about their bikes, since they are always getting roosted by YZ's, KX's, and RM's...

Totally just kidding. The rest of us are just getting ripped off! :)

 

[BONIFIED]

I just want to add that my name is Micah too. We also seem to share the same proclivity for catastrophic mechanical failure. Good luck bro.

 

[Micahdawg]

Thanks Micah...adding further doom to my experiences :)

Priced a head at the Zuk dealer....$127 with tax. Ouch. The part number is different from 01-02, but I wonder if any other year head will fit. Some dude on e8ay has a brand new 02 head for $100. Hopefully Eric can hook a brutha up.

Micah

 

[muddy226]

I may have missed some previous posts on this, but exactly the same thing happened to a new piston in my RM after having the cylinder re-plated, and was caused by the main powervalve protruding too far into the cylinder and snagging the top ring. The reason was that the powervalve is worn and has gone sloppy, allowing a side of it to protrude too far. I think that this excess wear was caused by cleaning the assembly with oven cleaner, which damaged the protective coating on the aluminium valve. A new one was quoted at £250.00, so the file was used. Its OK so far. I'd be interested to know what caused your piston to be damaged.
Incidentally, my piston was also a Wiseco, but I think that that is just coincidence, as I put a Wiseco in again and no probs so far. I wasn't so lucky with the head, but I put it in the vice on a power drill and cleaned it as best as possible, which wasn't very good, but it seems to run pretty good.

If anyone knows where I might get a replacement PV for reasonable money I'd be grateful !

 

[Micahdawg]

Actually, that is the first thing I thought of. The exhaust valve did not appear to be hanging out, but is very close. Since I have the jug off I will probably just grind a little extra off of it so I can be sure it won't hit the piston. I'll have to look at it closer, but the entire valve assembly may be able to be shimmed slightly. Good advice....I don't know if this contributed to the piston failure, but I'm not taking chances.

Micah