83 xj 750 idle problem

Been having this problem for a year now.

When I adjust the Idle screw so that the bike will idle properly and then open up the throttle the rpms stay high @ around 3 grand. If i back the idle screw out the bike won't idle without help from the throttle but if i give it gas the idle will drop back down to normal again that is to say it will die without a little input on the throttle.

I've cleaned the carbs...

fully broken them down and pulled them all apart. Cleaned everything

polished the bores....

Replaced the main jets which were wrong...
fuel float hight has been set.
Done everything i can think of and still can't get the bike to idle right.
I've housed everything down with wd 40 to check for an air leak and nothing. It doesn't make any sense?

Any guesses out there?

I really need help with this or it's just gonna be one of those thing i have to live with ...

Thanks!

 

I tried checking for air leaks with wd40 once. I eventually sprayed it into the airbox and still nothing. I'm pretty sure air is getting into the engine through the airbox. Next time I will try something else, like starting fluid or a propane torch. Something less viscous.

Also, at the risk of stating the obvious, ride for at least a half hour before you even think about touching that idle screw. And when you do touch it, a little turn goes a LONG way. Go for a 8th or 16th of a full turn each time and wait a sec for the idle to drop.

Last but not least, make sure your pilot mixture screws are at a good starting point. 3 turns out is where i started.

I'm assuming your valve clearances are good. If you can't idle you haven't synced the carbs.

I had problems getting my idle good too. The pilot mixture screw makes a huge difference. I'm still trying to dial it all in, but I get a steady idle.

 

are you running an airbox or pods. I learned yesterday on my friends 82 Kawi 550 that if the bike is jetted for pods and exhaust, (we only did the needle and main since that's all the kit came with) the pilot will need to be also be done. one of the symptoms for knowing that though is the idle will get higher as the engine gets warmer - hotter. Prolly not what you needed but wanted to share anyway. good luck

 

bump

 

Thank you so much for your post.
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i didn't see a running sync in the stuff you did, bench sync isn't good enough