NEED HELP...82 yz490 throttle stuck wide open

[mkpack77]

I'm still having problems with the throttle going to wide open with the throttle in idle position. I've changed out the crank seals, looked over the system and taken the carb apart and everything looks fine. Could it be the jets in the carb?? Any help would be appreciated.

[kwmotocrosspunk]

so when the bike is idling, is the idle raising itself to wide open?

if thats it, check your throttle cable, make sure it is well lubricated, not kinked or has any harsh bends or breaks, also make sure it is routed correctly as per the manual

[mkpack77]

yeah from idle it shoots full open, the cable is new and run properly. I can tell that the slide and cable are working because you can hear the slide hit top and bottom, so it's moving correctly with the throttle input. It's just that it doesn't matter where the throttle is, it goes full open. And that's what doesn't make since to me, how can it go full open with the slide full down/ in idle????

[2strkyz]

Check for a leak between the carb and the motor.

[kwmotocrosspunk]

oh ok, than you most likely have an air leak, either on the carb side or the engine side of the intake boot, since it is idling so high you can try taking a spray bottle filled with water, while its running, spray some water all over the intake boot(both sides), this should drop the idle(possible kill the engine but shouldn't hurt anything) if it does that take off your intake boot and check the sealing ability on it, check for cracks or tears on both sides, you might have an o-ring on the engine side which could be worn out and allowing air into the motor

[mkpack77]

thanks, I'll have to try that tomorrow

[nola_fiddy]

Just the thought of a yz490 2-stroke with a throttle stuck wide open sends a shiver down my spine!

[merlyn1965]

Check your boost bottle and the hose going to it, they do crack sometimes. Easy fix if it is.

[tirebiter]

Originally Posted by nola_fiddy

Just the thought of a yz490 2-stroke with a throttle stuck wide open sends a shiver down my spine!

Yep, especially nasty in the middle of the forest with a few hundred trees about...:hair raising

As to the original Q, look for leaks as described in earlier posts, and look for little burrs on the slide or inside the carb.
While the motors running, the slide gets sucked towards the engine, any nicks, ridges or free play on either the slide or carb body can cause a hang up.
That's why modern 4 strokes have 2 cables- push pull- no lawsuits..
BTW, rode/raced an 84 IT490 for 10 years..