Erratic Idle

[Anonymous]

I Recently bought an '81 GS750T and have just gotten it running after several years of sitting. It says in the manual not to touch the factory preset for the idle air screw, but I have noticed that most members of this board don't heed this warning. I have adhered to this advice so far but have run into some problems properly adjusting the idle. After the bike is warm, I try to use the large idle adjustment screw in between carbs 2 & 3 to get the idle between 1,000 and 1,200 rpms. But the idle will spntaneosly rev up to approx 2,500 rpms about a minute or so after getting it set properly. I have checked for vacum leaks by spraying carb cleaner on the intake runners without finding a problem. When i use the large idle adjustment screw to lower the idle once it has started idling at 2,500 rpms the the engine just dies. To get the engine to idle again I must crank the idle adjustment screw wide open after restarting the bike and then the whole process starts over again. Does anyone have any clue what is causing this freak condition and what I may do to alleviate it?

[Anonymous]

I had the exact same problem with my 82 GS650G. I ran the air screws all the way in (counting how many tuns out they were so I could rest if necessary) and set them to 3 1/2 turns out. That really helped with my bike, but you may also want to have your carbs sync'd too.

[Anonymous]

That's funny, I have an 82 750T - same problems... I currently have set them all to 2 out (due to the black plugs) and am waiting on my Carbtune II to arrive in the mail to sync them up.

If it helps I'll tell ya.

[Anonymous]

suposedly these screws only affect idle. make sure you did not tamper with the fuel adjustment screw on the bottom of the carbs and make sure you have no cracks in your vacuum line going back to your petcock. all of this can affect the idle.

[bybowtie]

I had a similar problem on my honda you may be able to Keep adjusting the Idle screw and get it right.... When I was adjusting the carbs on my honda as I would get close it would settle in where I needed it then run up a grand or so... Well after messing with all the carb adjustments(and fouling a plug or two) I realized that It had nothing to do with th carb settings when I got frustrated and turned th eIdle in a bit more... Well its been running and Idling great ever since and gets great mileage and no more fouled plugs!

[Anonymous]

Thanks!

Thanks for all your help guys after when I get my bike back from the shop with new tires I'll let you know what happens
Rob

[KEITH KRAUSE]

You're drawing too much air. The lean mixture is causing the high idle. Spraying the manifolds looking for leaks is sometimes difficult. Sure sounds like bad o-ring(s) to me. One o-ring went bad just 18 months after I bought my bike new.My bike did exactly what yours is doing. I don't know how old yours are but I bet they need replacing. Give them a good coat of grease and they will last a lot longer.

[Anonymous]

I may be the only person who didn't get this part, but Bad O-rings where? I'm having a similar problem with the idle adjust, and this could affect me, too.
J. Daniel

[lhanscom]

The O-rings are between the head and the intake boots. Take out the 2 screws that hold the intake boots on, and you'll find it.

[Anonymous]

High idle when warm

I have the same problem with my idle. COld its great. Around town on shor trips its great (1200 rpm). Aftyer about 15 mins on highway the idle is about 3k but will decrease to close to normal in about 30-45 seconds. SOmetime I have to tick the throttle to get it to drop.

I have already changed both the O-rings and the intake boots about a month ago.
So does anyone have any other ideas?

BTW My bike is not actually a GS its a 1983 GR650 but many of the parts and techniques match the gs series.

So if I alrady have th o-rings etc... done should I take it all apart and check it again? If so can I use the o-rings again?

Please help.

JB