i have finally got my 66cc ht installed perfectly and mounted nicely, and i've been breaking it in. As time passed i noticed that i was able to reach higher max speeds (this is normal) but now if i open the throttle as far as i can it will struggle to increase the speed and most of the time just stop powering. The engine doesn't turn off, it just goes slower than it should. This is odd and i cant think of why this happens because the bike now runs faster at a 3/4 throttle?
Engine Trouble Open throttle kills power
- Thread starter nashy10
- Start date
grinningremlin
Active Member
My guess would be an air leak.I've had them develop in fuel lines (bad black hose, ethanol and UV causes cracks you can barely see) fuel tank grommets, same thing.Or a leak around the carb.
wheelbender6
Well-Known Member
Agreed. Air leak. You might add gasket sealer to your intake gasket too.
Purple Haze
Active Member
Try raising the needle in the carb if you have the NT carb. This richens the mixture a little, it sounds like you are leaning out. Lowering the clip raises the needle. If it is only leaning out at wide open throttle, you may have to go with a larger jet. There is lots of info on these forums on how to do that.
HeadSmess
Well-Known Member
- Local time
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- May 17, 2010
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for full throttle, its the main jets too small, theres an airleak somewhere (which will also result in a high idle speed and hard starting) or the crank seals are gone. which usually means hard starting and a bad, erratic idle.
start with checking the seals, then the leaks, then all thats left is the jet!
start with checking the seals, then the leaks, then all thats left is the jet!
D
Deleted member 12676
Guest
possible leaks:
1) head leak (hint: stock heads and cylinders need to be planed to match well. lazy chinese *******s didn't do that)
2) crank seal leak (I have seen new right seals caught on the shaft lip and therefore not sealing correctly)
3) leak between carb and cylinder
1) head leak (hint: stock heads and cylinders need to be planed to match well. lazy chinese *******s didn't do that)
2) crank seal leak (I have seen new right seals caught on the shaft lip and therefore not sealing correctly)
3) leak between carb and cylinder
thanks guys i tried misting the engine while idling to check for air leaks, doesnt seem to be any unless theyre in the carb. Will adjust the clip and see if that helps. Also, i was under the impression that these bikes dont idle unless the clutch is pulled, am i correct? ive been riding the thing all along this way, the bike has to run at least 8km/h otherwise it quits (unless clutch is pulled) this is normal, right? if i let go of the clutch while stationary, itd die. also this thing is pretty hard to start, i have to warm it up for about 10-20 mins and open choke to get it running nicely, also noticing the exhaust gets considerably hotter than the engine, and a bit of white smoke. what does all of this mean? Also, the crank seal is something id very much like to check, but i dont know how. also the engine is custom mounted to the bike so taking the engine apart is quite difficult for me. oh, and just to add, the spark plug is also always a singed black, but it runs, and it has crazy vibration at low rpm
HeadSmess
Well-Known Member
- Local time
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what does a motorbike or car do if you stop without using the clutch? it stalls.
standard exhausts are POS. sounds like its blocking up or getting there. pop off its end cap and give it a soak with oven cleaner overnight.
white or blue smoke?
crank seals. take magneto cover off, four screws. any oil/fuel in there means seals gone. thats the first one to go as its only skinny.
take off clutch cover, five screws. look around the smaller gear for oil or fuel sprayed on case. yet to see this one pop
"singed black" is not a description for a sparkplug. google "how to read a plug".
loose motor mounts or rubber "vibration stoppers" will increase vibration, especially low speed. make sure everything is TIGHT and dont go thinking rubber will help.
mounts shouldnt make pulling the engine apart hard unless the installers done something weird and wacky, in which case, shoot them
standard exhausts are POS. sounds like its blocking up or getting there. pop off its end cap and give it a soak with oven cleaner overnight.
white or blue smoke?
crank seals. take magneto cover off, four screws. any oil/fuel in there means seals gone. thats the first one to go as its only skinny.
take off clutch cover, five screws. look around the smaller gear for oil or fuel sprayed on case. yet to see this one pop
"singed black" is not a description for a sparkplug. google "how to read a plug".
loose motor mounts or rubber "vibration stoppers" will increase vibration, especially low speed. make sure everything is TIGHT and dont go thinking rubber will help.
mounts shouldnt make pulling the engine apart hard unless the installers done something weird and wacky, in which case, shoot them
checked my plug, it looks fine, nice way between white and black, tiny bit of oil (damp). Checked the magneto, no oil residue or anything. opened the carb filter and it was full of gas, took it apart and cleaned it out. dried it. after putting it back on the engine had a really hard time starting and even running, had to turn in the idle screw. doesnt seem to be any more smoke coming from exhaust, but its substantially loud now. i tightened all the screws on the carb and it seemed to run good, so i took it for a 88min ride (pretty far) and on my way back it started making this loud scraping ish sound like a high pitched metal on metal type sound..still ran in fact actually better than before but now it always makes this noise... did my bearings sieze?
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