28mph to 22mph? 80cc chinese


Local time
12:04 AM
Apr 20, 2008
my bike is either a gallant white horse or a donkey.

according to my bike speedometer from fleet farm, my bike runs fine and goes 28mph (i don't crank it up that high for more than a few seconds, if i do at all) sometimes. most of the time, it is just stuck at this crappy 22mph, WOT.

i think it is a problem with the killswitch... here is why.

my dad and i put the engine on, and it ran like a top. in picture 1 down below, this is what it looked like about half an hour ago. when it could only go about 22mph. not sure what happened to cause the power loss.

picture 2 is what it looks like now. i switched the black and red wires from the killswitch around. i don't think it makes a difference, but much to my surprise, i hopped on, and boom! 28mph! i hit the kill to make sure it works. it killed just fine. i started pedaling, dropped the clutch, and 22mph. now i can't get it to go anywhere again past 22mph.

the speed dropped after i killed it once after switching the killswitch wires. coincidence? i don't know. the rest are pictures of the rest of the engine.

in both pictures, my thumb and forefinger are grabbing the killswitch wire.

the white wire is just taped off because that's the power from the engine, correct?

idler chain may be issue? i think it's good and tight, but not too tight... i dunno. end rambling. maybe someone has had this issue before. it's only been a few weeks since installation...

any help would be appreciated!


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It might be that the killswitch is still partially shorting the ignition - the stock ones are pretty much awful anyways - its worth replacing it.

Unless you made any other changes to the engine its going to be an ignition problem. A suggestion would be to remove the killswitch and run the engine like that for a quick test. If you regain your 28mph top end then you know the killswitch is the problem.

Check the plug for colour as well - you want a nice light tan, unless you are still in the running in period which may well mean a darker colour but I think its most likely something to do with the killswitch & ignition to be honest..

good luck.

Jemma xx
i unhooked the splice from the blue-blue connection, but left it grounded.

it did not make a difference.

i have a spare NGK-B6HS that i bought... brand new. hooked that up 3 minutes ago, along with a different spark plug wire i found in my garage. (my older bro's mazda won't be using THIS one!)

still has 22mph max speed.
looking at pictures I'm noticing that the master link clip is on backward (open end faces rear when on top/return) and the front motor mount doesn't seem to be a long term solution

what size rear sprocket are you running? is the the motor run in? what mix are you using?

I'm running 700c wheels and a 40 tooth and still on my first tank with a 20:1 and don't get anywhere near 28mph-no do I try. 22-24 is my average.

and without the kill switch connected? you need a control in your testing.

speed difference could be throttle related-I noticed the cable coming out of the carb doesn't look tight and straight up and down-I have a few threads showning on the barrel adjuster and a few at the throttle.

Anyway, I'm not sure the kill switch is related to the reduced speed.

how does it run? smooth, any hesitation?
hmmm the master link clip was never an issue before? because we had it on the other way, and it was binding inside the motor because it had that low of clearance at the angle it was going in on.

i have 26" mountain bike tires, and a 44 tooth sprocket. at the moment im running 20:1, and it's my 3rd or 4th tank of gas.

i think it runs just fine and dandy till it hits about 22mph... then it just feels like it lulls forward then i can feel it slowing down.

ill try tightening the cable.
i tried tightening the cable. it was already fairly tight. up on top, ive been slowly tightening it as the cable stretches.

riddle me this!

used a voltage tester, and the killswitch will not complete a circuit. the killswitch is whack.
i think you need to remove a couple of links. there is a reason you were told your master is backwards, it is because the thing is backwards. dont let the head bolts get loose, throw away crown nuts. search carb tuning. mitch
I see electrical connections that have exposed metal that may be touching the frame and shorting out. Possible for connectors to vibrate/resonate and not maintain good contact.
I see electrical connections that have exposed metal that may be touching the frame and shorting out. Possible for connectors to vibrate/resonate and not maintain good contact.

which would partially short the ignition and mean lost power? that might explain it
another place to check is equal spacing between the spinning magnet and the coil (equal spacing=equal voltage?). maybe use manilla folder for spacer (that's what I put in the space to remove it). good luck.