won't return to idle right away

[dgeorge]

Ok my 83 GS1100GK won't return to idle, once the throttle is release. It takes it about 30 to 45 seconds to drop back down. Any one have any ideas? I've checked the cable and it is not too tight or sticking the butterflies are not sticking open. What else should I check?

[Anonymous]

Check for intake boot leaks. Rev it up in neutral then spray a mist of water in the area between the carbs and engine. If the revs drop with the water, you have an intake leak.

Also, do a carb balance and idle calibration. Service manuals will have instructions. There are also some lurking around here somewhere...

Michael

[dgeorge]

I'm sorry I should have mentioned that I just rebuilt the top end with all new gaskets including the intake orings. I've been trying to sync the carbs, but when have it about right and I try to lower the idle down to 1000 rpms it takes about 45 seconds for it to change and by that time I've set it too low and it dies.

[earlfor]

Lean idle mixture probably. Have you tried lowering idle rpm with adjustment of the throttle plates and as rpm decreases, turn the idle adjustment knob in. Then continue lowering idle rpm with further throttle plate adjustment. This would richen idle mixture while turning the idle adjustment knob in for a lower idle rpm.

Earl

I'm sorry I should have mentioned that I just rebuilt the top end with all new gaskets including the intake orings. I've been trying to sync the carbs, but when have it about right and I try to lower the idle down to 1000 rpms it takes about 45 seconds for it to change and by that time I've set it too low and it dies.

[dgeorge]

Earl, I'm not quite sure that I follow what you are saying. I have the CV style carbs and there is only the one adjustment on the throttle plates where the idle screw adjusts them. Other then the ones used to sync them with #3. I know I probably sound like a dummy but could you explain this a little more. Thank you.

[earlfor]

Daniel, there should be two screws. One is the mixture (fuel and air combined) and on the linkage, there is/should be, a screw adjuster for each carb that adjusts the position of the throttle plate (the screw you adjust when you synch the carbs) Now, setting the position of the throttle plate controls the initial vacuum level. The velocity of the vacuum determines how much fuel is metered into the intake airstream. On CV carbs, the slides raise automatically by induction vacuum throughout the operating range, but the starting point, or at rest point, is controlled by carb synch and mechanical setting. The normal vacuum range at idle for your bike with stock jetting and pipes will be between 8 and 10 In Hg at 1200 rpm. Changing the vacuum at that idle rpm from 8 in Hg to 12 in Hg will richen the idle mixture inducted considerably. Closing the throttle plate causes an increase in velocity resulting in richening. Richening low rpm mixture may result in your needing to turn in the idle adjustment screw to maintain 1200 rpm. The idle adjustment screw raises all four throttle plates in unison..........which is the opposite of what you want, but you may need to, to keep it idling while adjusting vacuum levels. The bottom line is that if your idle vacuum is now between 8-10 in Hg, idle mixture is lean and you have maxed out the enrichment range on your idle mixture screws, then you still have some further adjustment possible before going to large pilot jets. If this last set of conditions is correct, then I would put vacuum guages on the carbs and synch the carbs with a 2 in Hg increase in vacuum levels across the board. That you bike will slowly return to idle says that it is not extremely lean. A couple inches change in idle vacuum level should solve your problem.

Just an edit......... There is a synchronizing adjustment screw on carbs 1, 2, and 4 only. Carb 3's baseline setting is controlled by the idle adjustment knob, so you must use that to set #3 to the vacuum baseline you want, then merge 1,2, and 4 with it. You will probably need to adjust #3 multiple time to maintain the correct vacuum as it will change slightly as you change settings on the other carbs.

Earl

Earl, I'm not quite sure that I follow what you are saying. I have the CV style carbs and there is only the one adjustment on the throttle plates where the idle screw adjusts them. Other then the ones used to sync them with #3. I know I probably sound like a dummy but could you explain this a little more. Thank you.

[dgeorge]

Thank you Earl, I think I understand now. , the only time I've ever worked with more then one carb was on a race car, and it wasn't nearly as confusing as this thing is. Again thank you Earl for taking the time to explain things on a level a novice can understand. You are a very good teacher, and instructor.

[jjnorc]

I the carbs were OK before they should be OK now, Don't mess with them.

Double check the CAM TIMING. If you're CAM's are advanced one tooth
on the chain the motor won't return to idle as it should.

I just did a rebuild and the same thing happened to me. Reved high for 30 seconds then returned to idle.

[dgeorge]

JJ, when I was rebuilding the top end I also rebuilt the carbs. I'm almost positive the cam timing is correct. I had problems with the cam timing when I put it back together the first time, so I'm pretty sure it is the carbs. I'm waiting on a starter for it right now, I had gotten everything back together, after having a broken cam cap bolt taken out at the machine shop and was syncing the carbs, almost had them in sync and went to adjust the idle down a little and it didn't drop so I adjusted it down a little more and it died. Went to hit the starter button and all I got was a click so after some trouble shooting figured out it was the starter again so I bought one off of ebay, should be here either tomorrow or friday. Just trying to get prepared for when it gets here. Thanks for your advice and help though.

[earlfor]

:-) :-)

Earl

Thank you Earl, I think I understand now. , the only time I've ever worked with more then one carb was on a race car, and it wasn't nearly as confusing as this thing is. Again thank you Earl for taking the time to explain things on a level a novice can understand. You are a very good teacher, and instructor.