Throttle increases on its own.

[nickitzi]

1981 honda ATC200 all stock but Clarke fuel tank.
Throttle will increase to full open with out touching thumb controller , no kinks in cable, return spring new, it seems to be in the carb itself, when it winds out there is still full thumb controller response. only way to return to idle is to shut off engine and restart. Its not the cable or tank interference. Checked slide for burs none found guide
is clean no burs. idle screw makes no difference turned either way. I'm lost. Please help!!!!!!!!!!!

[Xpress]

Sounds like something is pulling on your cable. Without a load on the engine, even a little bit of throttle can lead to the engine running very high RPM's.

I know if I move my cables on either of my trikes then they will rev the engine.

[sunbaby69]

check fuel line/carb for air leaks?

[nickitzi]

I replaced throttle cable with new honda replacement, this happens with or with out tank on it, speed increases with out any help from me. It does not seem to be cable related, what is strange is it does not respond to the cable at all.

[Rjfabwerx]

I had a Yamaha dirt bike do this...think it had something to do with the rubber piece between the carb and engine...was cracked pretty bad so plenty of air leak...pulled that off and taped it up tight and it stopped doing that and had alot more power...not sure if this was the problem with my bike but it did seem to help tremendously...

[nickitzi]

I rebuilt card with genuine honda parts including intake manifold what is puzzling is whats pulling the slide up?

[leviblue]

air leak.... check the inlet between the reeds and the carb for a pin hole or cracks in the rubber

[nickitzi]

Checked for leaks with wd40 spray no change in idle, this will run fine for most of the time but there will be a sudden burst in speed then it will miss and fowl the plug. After 5 minutes of down time it starts right up will run then idle up again.

[KASEY]

air leaks.. lean condition.. did it do it before you changed the cable?

[nickitzi]

Yes that was the reason for the cable swapout

[nickitzi]

Found out the problem the spring clip to hold the needle in the slide broke in two places. This caused the needle to slip up into the slide causing the high idle and also fowling out the plug, also this led to damage to top of slide. I replaced the slide and needle and retainer clip and we are back on the dunes this morning, thanks for all the help.