98 rm250 puzzle

Discussion in '2 smokers' started by Jayrod1318, Jul 23, 2014.

  1. Jayrod1318

    Jayrod1318 Poster

    Joined:
    Jun 14, 2011
    Oddometer:
    1,683
    Location:
    Here and there and stuff.
    So My brother picked up this RM for a song, it had been sitting for 6 years or so. PO parked it because it was acting up and running poorly.

    Bro does everything I tell him to do, disassemble, clean, lube, check wheels, clean filter, clean tank, clean carb, adjust clutch, check fluids ect. new plug fresh premix.

    Come to find out after washing the muck off the bike is in great shape probably less than 50 hours on it.

    Bike fires up and he rides it a few times for several minutes each with no issues. Gets the idle set on the carb, reports having trouble setting the idle...

    Fast forward the bike dies one day after running for several minutes. Won't start up again. Checks spark, gas, and compression by "feel". Checks out, it should run! Bike will not start. This happens on 2 different occasions. runs fine, gets hot, dies. has spark, gas and compression.

    We both decide to inspect the top end, bro takes apart and notices a small scuff on the intake side, nothing major we think. He takes piston and jug to machine shop to get checked out. everything looks good, machinist scuffed the cylinder up. he also got new rings and gapped them for him. piston is fine enough.

    Bro gets the bike back together today and gets it running. takes it for a few short trips around the block. runnning for maybe 20 mins or so. bike dies, won't start. Spark, Gas, Compression. nothing:huh.

    I'm thinking electrical issues myself, bike gets hot, coil or cdi malfunctions. Throws weak spark or bad timed spark? Remember he insists it has spark immediately after dying..

    However my worry is now an air leak? or a bottom end leak? When it was running he having a hard time getting a good idle. This would certainly cause that.

    Maybe we have two issues going on? air leak, and electrical issues? Or maybe an air leak that gets really bad when the engine gets hot?

    I was very admit if he gets it running again to check for spark right away when it dies..

    any thoughts?
    #1
  2. MATTY

    MATTY BORDER RAIDER

    Joined:
    Jun 23, 2014
    Oddometer:
    701
    Location:
    England On the Scotish border
    If you have cleaned the carb / tanks clean/ fuel through tap/spark. It sounds like you have good compression what with your new rings etc, it would be a good place to continue these investigations with crankcase compression in my opinion.
    Had a Yamaha DT pop out the crank sear at rear of flywheel once it had been playing about much as you say the RM is, and i could only guess it was just in enough to keep compression untill it poped out.
    I pushed it back in did not even replace the seal and it never gave anymore trouble after that.
    I blamed the seal coming out on the DT having a drink one day crossing a river it stopped allthough i got it running fairly quickly it was not long untill the problem seal croped up, pehaps your RM has been in water something like that check the seals are not coming/ come out.
    #2
  3. Kevin K

    Kevin K Adventurer

    Joined:
    Jul 20, 2008
    Oddometer:
    64
    I highly doubt it's an air leak
    Sounds like an ignition issue to me

    I bet it's the stator

    When I was a boy I would have done anything to have a old man into bikes like me around. I'd be working in his garage all the time.

    Kids around my house don't even turn thier head when they see my bikes in the driveway. I suppose thier interest is on Call of Duty
    You are fortunate to have a brother into bikes who is a good kid
    #3
  4. Jayrod1318

    Jayrod1318 Poster

    Joined:
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    Here and there and stuff.
    35 year old kid:clap

    Your right though, we grew fixin and wrenching... I'll teach my boy the same.
    #4
  5. 13.1

    13.1 Shaken not Stirred

    Joined:
    Oct 6, 2006
    Oddometer:
    403
    Location:
    Way up in the White Mountains of Arizona
    I agree with Kevin on this as the evidence points to the ----->S T A T O R

    as the RM HEATS UP :evil
    the stator takes a break
    and then after it all cools off and feels better
    ---> she run again (but only for a bit) :lol3
    ...classic old 2-stroke ignition go-kaput
    #5