rm125 ?

[redsput]

Tried out a 97' RM125 tonight. The bike started right up and seemed to run great. I'm wondering about performance (it's all stock.) I'd swear my kid's current 03' kx85 (also stock) would spank it. Is this normal, or something wrong with it? (I really expected a lot more...)

 

[2smokers]

I have a 96' RM125 (pretty much the same bike), with a fatty pipe, boysen reeds, twin air filter, and there is no way a 80 would come close to it. How does the bike run, does it bog? If jetting is good and the compression, it should rip.

 

[Kevin003]

It probably needs a new top end. That how mine was when i bought it. Put a new one in and it rips hard (for a 125 that is) :nener:

 

[Truckman]

My old RM 125 is worn out but it will still put the lights out
on my sons new YZ85 with ease.

 

[railer]

My RM125 used to belong to Buddy Antunez and it pulls like no other. All it really has is Vforce reeds, Bill's Pipe, FMF TurbineCore II (put on after I acquired it), Wiseco Piston, everything else, engine wise, is stock. I love it. I got it almost a year ago, haven't done a thing to it, and it's still pulls like it did the day I got it. Good bike.

 

[kx125412]

the powervalves might be gummed up with carbon and stuck wide open or closed, i would check those out

 

[railer]

are you buying a used bike or is it already yours? I'm confused...

If you're buying it, negotiate the price for having to tear it down and find the problem.

A bike as such should be torn down anyway just to make sure everything's copasetic. I would look at the piston and cylinder no matter what the bike was running like just to make sure it had a good crown pattern, not to mention making sure the piston wasn't about to grenade.

Once that's done, then start troubleshooting other options starting with maybe some re-jetting which is unlikely the problem but should surely be verified before more is done.

Hope this helps.

 

[redsput]

The bike is technically my nephews yet (who is off at college and disinterested.) He wants to sell - but couldn't get anything without it running. I told him if I could make it run right I'd buy it from him for my kid (if not, he can try his luck at selling elsewhere - and my labor will have been a donation to his college fund.)
It has a new sleeve, piston and rings (not broken in completely yet.) I rejetted down to 48 pilot, 172 main. Checked the reed and found an air leak at the cage (gasket was left sticking out when he assembled it - doh~!) Found the airscrew in the carb was broken off inside slammed tightly shut (fixed that.) Found the exhaust pwr valve was not connected (fixed that.) yeah - I wouldn't hire him as a mechanic either! It really seems to run good now, starts easy, no sputters or bogs anywhere, sounds tight and clean - but it's a pig. I'm out of ideas - not really sure what to look at next. :think: maybe I'll rip the jug off to check things out if the weather doesn't agree with riding this weekend...

 

[2smokers]

Have you checked your compression yet?

 

[redsput]

Here's something odd (at least compared to to the KX's I'm used to wrenching on..)

When I reach into the port (via the reed block hole - reeds obviously removed.) The cyl sleeve sticks down about 1/2" - roughly 1 1/2" wide into the intake port.

Also, just before the finger reaches the sleeve - if I curl the pinky up I can feel a big flap of what seems to be a gasket hanging there.

Geeze - Now I'm wondering if the right sleeve and gasket set was used :bang:

The boy did seem confused as to the actual year of the bike. It's a 97' per the vin, but he kept telling me 99'. Anyone know if the cyl jug design was the same those years? (feels like this is fast approaching "wasting my time" status.

 

[2smokers]

No those years do not have the exact same jug.