New to me, 1985 rm250

[KieranM]

yes its best not to use ether as it starves the engine of any lubricant, be it only for a few seconds, wd40 used to work on 2 strokes but then they removed something that would aid in the combustion (not sure what), im also on a pocket bike forum and many think that ether is the way to go when the engine has been sitting, total bull**** one of the reasons why i left the forum, not many cared for there bike and then come back asking why its ****ed up.

What colour spark are you getting?

 

[Kaptain Krunch]

Kenny, new plug is the first thing i did. I've tried new, old, and known to work plugs, kieren, spark is nice and blue, plenty strong.

 

[mike75925]

kapn, have you checked the reeds? on 2 strokes, the keys shear pretty often depending on riding style. the main things to check when they don't run is fouled plug and sheared key. anyway, a younger guy was trying to get a yz85 running and couldn't. i just happened to be over at the time, so i took a look. the carb had old gas, cleaned; then i looked to see if the reeds were good. they reeds were glued by old gas. i cleaned them. they were slightly open. i unscrewed them and flipped them over. cranked right up. btw, this guy had a '94 rm250 that he gave away. fresh powder coat, fresh engine etc. do you have suction? if not, you probably need crank seals.

 

[mike75925]

check the stinger for crap.

 

[Kaptain Krunch]

Done all that, reeds are mint carb is min, flywheel key is fine, i have suction, pipe is fine, silencer is not clogged but does need to be repacked. Looks like the only thing left to try is getting the proper stator.

 

[mike75925]

check rm stator, they have a 1 year warranty, and offer hotter parts.

 

[Kaptain Krunch]

What kinda compression are these bikes supposed to have? Test came in at around 110 psi, which i would thibk should be enough to run, but it is still time for a top end. I had a 185 free air that ran at 85psi, and started within 10 kicks haha.

 

[mike75925]

i think they say 90 is the lowest it will run on. but then, i've seen a bike run on less than half of a ring. question, why do they say to do a comp test when the engine is warm? that sounds counter intuitive. if the thing doesn't have enough when cold, how are you supposed to get it warm? a block heater?

 

[crazycart]

I would rebuild it...110 is a bit low for a large mx bike.....at least pull the top end, re ring and hone.

 

[Kaptain Krunch]

So 110 isnt even enough to run? Rings wont hurt anyways, i guess i should do that before i replace the stator.

 

[crazycart]

I would say the stator is also the problem. I would imagine totally different timing on a 125. 110 it may run..but i couldn't say for sure, when my bikes get into the 130-120's i rebuild them. That bike should have 150+

EDIT while your at the stator i would replace your crank seal....bad or not. Just take 2 wood screws and screw them into the seal on each side until it pops it out, lube and tap in the new one...

 

[Kaptain Krunch]

I would say the stator is also the problem. I would imagine totally different timing on a 125. 110 it may run..but i couldn't say for sure, when my bikes get into the 130-120's i rebuild them. That bike should have 150+

EDIT while your at the stator i would replace your crank seal....bad or not. Just take 2 wood screws and screw them into the seal on each side until it pops it out, lube and tap in the new one...

alright, well rings are cheap enough, so i might as well. Its a single ring piston i believe, and the ring is under $20 with shipping. Stator is around $70 shipped, and ill probably replace both crank seals while im at it, the flywheel side looked like it was getting a little brittle to me.


EDIT: Ordered rings, top end gasket kit, and the right stator.

Total: $107 not bad, total into bike as of now is exactly $220.

engine is out, noticed a few things. Shifter shaft and clutch cam shaft are both sloppy, cases were welded in front of output sprocket (threw chain at one point), and the drain plug is stripped and stuck in the cases (F#$@).

Bike has a newer gas shock (same as my friends 96 cr125 rear shock). Rear wheel bearings are going. All plastic chain guides need replacement. chain and sprocket look newer.

Cant wait to get this thing goin!!

 

[crazycart]

Wow that's odd that it has a single ring....every 2 stroke bike i have dealt with has had 2. I have only rebuilt sled engines that have had 1. For what you have into it, it is still a good deal. When you buy a bike that cheap they most likely need lots of work. Sometimes you get lucky, sometimes you get a turd. You know how it goes. It'll be worth all the work and you will be flying by your buddies with the front end hangin'

 

[88s10Durango]

Hi , when u pull the piston check to see if its a Weisco , alot of them had 1 ring ??
If your still having probs , contact RickRacer on here , he has the same engine in his Go-Kart and is a licensed mechanic at that ,, Bill

 

[Kaptain Krunch]

Piston appears stock, bore looks pretty clean (hone marks still visible), ring end gap is .037" not sure what the tolerances are. Piston wash looked good, dialed in perfect. Rod feels decent, crank bearings sound good.

I took the sidecover off to drain oil and check clutch/bearings. Guess what?! one of my god **** clutch plates (fiber) was broken in 4 spots, and a piece is missing! ****! So, i guess i have to do some search and rescue, then find another clutch plate. The clutch basket bearing is also shot...bad luck...

also, upon further inspection, the engine was actually welded back together in two spots...by the clutch cam where it must have thrown a chain, and right around where the shifter shaft goes in, im assuming someone dumped it and it ripped the shaft right out of the case. Good news is the welds look great haha.

and in other news, got my license today on the first try! so im gonna be gone for a week or so finishing up my truck...

 

[Kaptain Krunch]

Rings and gaskets are in, just need to figure out the torque specs and i can toss the top end back together. I ordered the clutch plates and they should be here next week, hopefully i'll be breaking her in by next weekend. Cant wait to ride this thing, gonna be a fun bike. I'll get pictures in the next couple days, im cleaning up the frame and repainting it the stock blue, engine is all clean and shiny also.

 

[jr dragster T]

Wow that's odd that it has a single ring....every 2 stroke bike i have dealt with has had 2. I have only rebuilt sled engines that have had 1. For what you have into it, it is still a good deal. When you buy a bike that cheap they most likely need lots of work. Sometimes you get lucky, sometimes you get a turd. You know how it goes. It'll be worth all the work and you will be flying by your buddies with the front end hangin'

I've seen a couple single ring motors, 2001 CR125R, 2003 CR85R etc. I think most of the big 250's are dual ring though.

 

[Kaptain Krunch]

Yup, it is indeed stock. my buddies 96 cr125 is also single ring.

I'm getting close to running this thing, got the motor back in, painted the pipe with some stove paint, cleaned up the frame, just waiting on my clutch basically. Planning on going riding this weekend if shes going and broken in by then, im psyched!

 

[Kaptain Krunch]

Almost 100% back together. Clutch is in, hopefully ill get her started up tomorrow. Shes got 170psi compression cold without even breaking in the rings.

 

[KieranM]

sounds like you on to a nice one there

Dont forget a few pics