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wont rev past 4k

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by MrWasabi, Nov 11, 2007.

  1. My dad bough a susuki gsx250s 85 model the other day.

    Previous owner had it for his daughter to get her L's on and then she moved on...now i dont know what they did to this bike, but it will not rev past 4k. As you open her up on any gear, it will reach 4k and then start to sputter and lose all power the the back wheel...untill you shift up and the revs drop and you have about another 2k revs to get to the next gear.

    any ideas what this could be? i was thinking carburator but i dont want to be pulling the bike apart for nothing
  2. stator coil
  3. oh, say any one of half a dozen things..
  4. Could be anything and you have not described what it does to help with a diagnoses.

    Take it to a bike shop or spend a year guessing :LOL:
  5. When you get a bike like this you need to spend a bit of time on it getting some basic things right.

    Put some new plugs in it. That could solve the problem by itself. Check the air filter is clean and clear of blockage.

    The inlet to the air box is under the seat. Make sure there's not rag sitting under there or similar.

    make sure the vacuum and fuel lines to and from the carbie and fuel tap are good and attached properly..

    make sure there isn't a huge lump of crap in the exhaust.

    make sure the tank vent is clear.

    when you've done all that (probably a couple of other things I'm forgetting) then the next suspect will be the carbies themselves.
  6. well i described as much as i could.
    while riding the bike if you open her up, the engine will begin to sputter at around 4k rpm. loses power completely, until you change gears, the revs drop down to about 2k and then you have another 2k before you get to 4k and thats where it starts to sputter again and lose power.

    The intake under the seat is clear and has a new filter on it, there is nothing i can see clocking the exhaust, might try the spark plugs as you suggested then look at the carbie
  7. Doesn't like being on the main jet, by the sound of it.
  8. Yep could be a blocked main, could be a hole in a diaphragm, or a stuck slide, but it could also be a partially block fuel line, a blocked fuel filter, tap or even a tank vent.

    Get the other stuff right before you crack the carbies.
  9. 10$ says he will take it to a mechanic
  10. well i went down the to local spare parts shop and picked up some filters (oil, fuel, air). The guy told me that he had changed them but who ever believes anything they say...
    air filter was spick clean, but i changed it anyway, oil filter was a bit mucky, fuel i couldnt really tell so i changed it. took it out for a ride and no dice, still sputtering.

    by this point i had enough so we pulled the engine out, i had planned to just clean the carby, but someone else had better ideas to strip the whole motor apart...

    ok ive done this many times on cars before, but ive never touched a bike engine before...how hard could it be...

    worked into the night, cleaned every bit of the engine as if it were new, and typical me by the end i had a bolt left over...who knows where it came from...

    cranked the engine...VROOM!

    started first go...we both look at each other and wonder had we actually got this right the first go...

    still i looked in my hand and saw the bolt and wondered where it came from...

    i got on and reved it to 4k...5k...8k.. ok thats enough changed gears...

    works like a charm. I am sure it would have been the main of the carby, but rebuilding the engine sort of gave it a new lease on life, certainly feels that way anyway.

    Thanks for the tips guys, encouraged a fun 2 days of work and a crash course on motorcycle repairs :D

    Edit: btw i want my $10
  11. The bolt left over must be the rev restriction bolt. :LOL:
  12. lol at the bolt left over gotta hate that. personally i'd pull it apart and spend a couple of days trying to figure out where the bolt came from (olny to find out that it was from a pool pump i'd pulled apart a week prior). great work on getting it going nicely.