no more high rpms:( (after tear down then put back together)

Discussion in '2-Stroke Engines' started by f4lloutdiablo, Dec 6, 2009.

  1. f4lloutdiablo

    f4lloutdiablo New Member

    hey everyone, i recently had my bgf motor apart and was just having fun and looking at how these things work...... then yesterday when i had it all back together and started riding it would not get any near the rpm range it used to get while i was riding. i even took out the stock (2 head gaskets)
    and replaced them with one new one. Im sorry i forgot to mention i had the motor broken in very nicely and it ran great but it was apart for two months but with towels over it so it didnt get dirty. i even matched the intake gasket to the cylinder body for better performance. The problem is that when i accelerate it makes a distinct smooth noise (i dont know if that is 4 stroking or two stroking) but then it tops off at what used to be my half throttle. When it tops off it sort of acts like it is missin one or two beats of combustion. this bike used to get up 35 mph and now im having trouble makin 25 mph:( anyone with information that can help please reply
     

  2. give me vtec

    give me vtec Active Member

    don't ever fix what isn't broken... you just get an unnecessary headache most of the time.
     
  3. f4lloutdiablo

    f4lloutdiablo New Member

    well ive come to tell myself that i made a stupid decision.... but if anyone can help please do so
     
  4. AussieSteve

    AussieSteve Active Member

    Have you cleaned the carby thoroughly?
    If it sat for 2 months with a little fuel in it, when the fuel evaporates it leaves an oil residue that might be blocking things up.
    You say you had your motor apart. How apart? Did you split the cases etc or only strip the top-end?
    To me, it sounds like a carb and fuel/air mixture problem. (4-stroking from a rich mix.)
    If you haven't changed jetting or needle height, then more than likely there is some c r a p in the carby float needle seat or possibly your float level was accidentally altered.
    Also check for fuel flow from the tank, exhaust clogging, clogged air filter.
    ... Steve
     
  5. f4lloutdiablo

    f4lloutdiablo New Member

    aussie i did a quick check on the jet with just my eyes and looking throught it into the light and i didnt see any restrictions. i never checked the air filter and i did split the crank case. it was basically a full tear down. but the thing is the engine runs great at idle but then is wierd after that. i did change the needle and lowered the clip one grove and that barely helped the problem. It sort of got it to go to 29 mph instead of 26 mph. do you think i would need to make the main jet smalller or larger or maybe its not the problem? i havent tried to check the fuel flow from my tank but when there is no fuel in the lines the on off valave slowly drizzles the gas to eventually fill the hose up then i use the tickle thingy to prime the carb. could the valve be a factor also? i never found myself checking for a clogged exhaust either. i may do this all tomorrow after school.
     
  6. AussieSteve

    AussieSteve Active Member

    Are we talking about the same thing? The main (slide) needle jet is in the middle of the carb body, protruding downwards with the main jet screwed into the bottom. I didn't mean this one.
    Instead, if the pivot pin is removed from the two-fingered brass tang that the float engages and it is removed intact, there's a seat under the attached needle. The fuel line goes on the other end, on the outside of the carby. Any junk in this one will cause flooding and a rich mix.
    (I'm not sure, you might have already known which one I meant.)

    Check the air filter.
    If you split the crankcase halves, you might have a leak at one of the crankshaft seals or the crankcase seal itself might be leaking. Did you fit a new gasket? Did you use a sealant?
    You shouldn't need to change the slide needle setting if it was OK before. Same goes for the main jet.
    If I were you, I'd set the slide needle back to where it was when the engine last ran well, check everything else and if nothing can be found, raise the 'c' clip on the slide needle one notch, (lower the needle), to make the mixture a little leaner and see what happens.

    Yep, the internal filter on the fuel petcock might be blocked and if you have an external inline filter, it may be blocked or too restrictive. Just pull the hose off the carb, point it into a jar and turn the tap on. Check for flow. It should be able to flow much faster than your bike can use fuel.

    Possible, but do this last - it's least likely if it was OK when the engine last worked properly.

    Plug colour is the best indicator. black=rich, white or whitish=lean, tan=OK

    Let us know how you go,
    ... Steve
     
    Last edited: Dec 7, 2009
  7. f4lloutdiablo

    f4lloutdiablo New Member

    alright well yesterday before i posted i did check the plug and it was darkish brown/tan and a little wet. but everything else i cant do until later tonight. i will keep posted.
    thanks aussie!
     
  8. f4lloutdiablo

    f4lloutdiablo New Member

    ok heres the final report..... i took the air filter out cleaned it and modded the four little tube thingys on it so that they let more air flow in and this thing went right back to how it used to run.....sorry for the trouble anyone.
     
  9. AussieSteve

    AussieSteve Active Member

    No trouble, at least it's fixed.
    I did the same to my air filter, as a temporary measure. I'm buying a better one from SickBikeParts. (The slimline version.)
    ... Steve
     
  10. f4lloutdiablo

    f4lloutdiablo New Member

    thank you for the help steve. i am glad a resolved this but the fact is i was eventually going to mod the intake to accept a cone type filter and i was going to fabricate a mount so that it angles to the side to clear my seat tube. the filter i have is almost four inches long and allows a good flow of air so im happy to know that i now can start the mod.
     
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