01 rm 250 vs 99 yz 250

[skidmorejr88]

Ok guys heres the run down i went and brought my dad a 99 yz 250 for xmas hes retiring 2012 from the county pd and i wanted this to be special. Ofcourse after picking it up for him i went over some little things and made sure its ready to go xmas day with that being said i had to give her a good ride to make sure the bike was running properly:twisted: and man i was in for a suprise i had a hard enough time keeping the front end down, and the bike is all stock except for protaper handle bars. So i went out and had it set in my mind i need something to keep up with the old man now. So i picked up a real nice 01 rm 250 today that has alot of aftermarket stuff on it and agin got a great deal on it. After i got home and fired it up i kinda was a little disapointed it just didnt have that effect the yz does i can really feel the powerband in the upper range of the rm but the low end just is not really there. Like i said it has alot of aftermarket stuff like fmf fatty pipe and silencer boysen reeds and the suspension is worked. Is this just the nature of the best? Is it just a mid-top end bike? Or is something wrong? From what i have read guys seem to have a problem with handling the power of this thing but to me it just feels like its not hitting as hard as it should. :wondering

[1tonofsh!t]

Carb jetting could be your issue especially if he never changed it for the perform. parts. Also do a compression check. You will definitely see something like you have if your top end is on its way out. Good luck...report back

[skidmorejr88]

Ok I will go home and do a compression check tn better keep my fingers crossed.

[skidmorejr88]

Well u hit the nail on the head with that one all I could muster that beast up to was 120 psi:( guess I will be doing my first top end rebuild.

[300rman]

Powervalve not operating could also cause the motor to have a odd powerband.

at 120PSI, it should kick over pretty easily.

when you did the test, did you hold the throttle wide open?

[skidmorejr88]

Yea I did have it at wot when I was kicking it to test compression but I did not hold in the kill switch but did not see where that would make a difference in my pressure reading. It is fairly easy to not the easiest bike ever but not at hard as my dads yz.

[300rman]

because if the motor even partially fires, it could give a higher compression reading.

[skidmorejr88]

Thanks 300rman so it could be even lower than 120psi? :o I'm still going to do the top end rebuild any way it seems very straight forward and gives me a good sense mind. One question do I have to have the cylinder replated if there's no scoring and still cross hatch markings?

[Micahdogg]

I've had a couple RM's, last one was a 2001. When they get to about 100 psi, you will have a hard time keeping a plug in them. They still run acceptible in the power dept though.

And my 2001 was a tractor. It was all low end with a huge midrange snap. IF that is what you want, I'm sure you'll get it. It got annoying to me after a few years though because I mostly trail ride and it got to be a chore to keep it pointed straight while attacking the woods. And a flywheel weight will NOT help - it will just make it wheelie easier.

As for the cylinder, if the plating isn't chipped or flaking, just have a shop hone it. You will probably have to remove the power valves first -but they are fairly simple and probably need a good cleaning anyway.

[300rman]

If the plating looks good, DO NOT DO ANYTHING TO IT. Dont hone it, nothing. The plating is very thin, but very hard. It is meant to keep putting pistons into until the plating gets damaged. If maintained properly, a plated cylinder will last through 10+ rebuilds.

[Micahdogg]

I disagree. The plating is very hard, but it will still get a little glazed over the course of a piston/rings life. Sure you can probably rebuild it and have it run fine, but getting a good cross hatch again will only give you more life from your next rebuild.

AT a mininum, try to work a nice cross hatch with a green scotchbrite pad. If you can break through the plating with that, then your plating was shot. But around here our shops only charge about $10 to hone a cylinder. It's just good maintenance.