Top speed Jerking?

When i have the throttle all the way down the moped feels like the brake is grabbing. Yet when it does it the engine doesnt lose any rpms but never goes any faster. Im confused i switched the coil the plug everything to the the ngk brand yet it still does it. I have a Tomos a-35 with a airasal kit 58 jet a tecnigas next pipe. Its weird i even changed the trans fluid just to think it was slipping at top speed but still does it. Do i have a bad connection somewhere or is the engine not ingadging. Im confused beyond belife can anyone plz help me i have a race coming up.

Re: Top speed Jerking?

it could be a drive clutch!

Re: Top speed Jerking?

Sounds like the second gear clutches. I'd tear into the tranny and take a peek at your Cork-JUNK clutches. Don't feel bad if there isn't any material left, because Tomos made the material out of cork. Cork as you know is very soft, and should NOT be used for clutches in mopeds. I like the A-3's myself.....

Re: Top speed Jerking?

Dan Ackroyd /

Ok its not jerking really at top speed it sort of feels like someone is hitting the brake. Motor sounds fine and also it doesnt start doing this until it warms up after riding for about 2 mins oour so. And also does a washer go on the shaft of the clutches i put one on the gear shaft and the trusts washers on the pedal shaft. Plz i need help.

Re: Top speed Jerking?

Dan Ackroyd /

I didnt think it was that because i got this engine that i put on it with only 1500 miles on it.

Re: Top speed Jerking?

If it's not the brakes grabbing, then your engine is missing and causing intermittent lack of power. There are many reasons why an angine misses. Could be as simple as bad gasoline. Could also be a bad spark-plug, or coil. Troubleshoot systematically, post results.

Re: Top speed Jerking?

Dan Ackroyd /

Changed the gas not the plug changed that not the coil all brand new same as the black box were the copil goes. When i had it before the moped blew up so i replaced it Well when it blew up a peiace of metel broke a little peiace of the bottom of the head were it slides into the engine and also Srahed the piston, So me and my father sanded the cylinder down so it didnt scorched anything. Yet it runs godd yet when it warms up and you at top speed it sounds like a pieace of metal is being thrown around in the piston. Ive. ruled out the tran. Would thicker trans fluid work or would replaceing the head and piston be best. When it gorged the piston it was beside the piston and i changed the trans oil no metel came out good sign.

Re: Top speed Jerking?

Dan Ackroyd /

Ok im think its the piston slapping agaisnt the side wall slowing me down because the moped is looseing speed and power.

Re: Top speed Jerking?

I'm not completely understanding, But if the engine runs better with a higher octane gasoline, the choke on, or with a bigger jet size, then your engine could be detonating. The flame front in the combustion camber is traveling too fast causing an explosion instead of controlled combustion. Hope it helps

Jonathan

Re: Top speed Jerking?

Brian Mikami /

I was 4 stroking with a similar 'brake grab' feel amongst other issues. I suggest you do a run with the air filter OFF. Worked for me, now I a screen filter and it flies...plug color is perfect...not black like it used to look. Metal sounds are bad so you may need a rebuild, but try that first, just for one run and see if it helps.

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