1985 with a rough/surging idle

[v-max 4]

I've got an '85 with stage seven and a full Kerker exhaust that has always run well. This year it's developed what I would describe as a rough or uneven idle. It will also sometimes hold at an rpm when the throttle is released(usually low speeds) for a few seconds before coming down to idle. Also at low speeds the exhaust will sometimes pop or backfire a little when the throttle is released. Engine seems to run fine with lots of power at highway speeds. Lots of spark and all spark plugs look ok. I've cleaned and re-sync'd the carbs and changed the fuel filter. Like I said, it's always been a strong runner so I don't have a lot of experience trouble shooting this bike. Any help would be much appreciated. Thanks.

 

[CaptainKyle]

First off welcome to the forum. How did you sync your carbs ? Do you still have the vboost where you can close it down to sync or was it removed ?

 

[SpecOps13]

Do you have Ethanol in your gas??? Could be what Kyle asked for sure but it could also be from the gas if it's Untreated Ethinol... Sea Foam or more will help if that is the case........


Welcome to the Forum Too..

 

[v-max 4]

No, I don't have the old v-boost anymore. Instead I used my Uni-Syn tool (made by Edelbrock) which allows me to do each carb seperately. I have adaptors made up for the intake of each carb to allow for a proper seal. I don't use the Ethanol blended fuels... same fuel as always. Also, in my earlier post I forgot to mention that although it sounds like the throttle linkage might be sticking I'm sure that's not the problem.

 

[SpecOps13]

What is your battery voltage at idle? If it's low there won't be enough for good ignition... Once the revs are up the voltage may be coming up too, letting it run better... Just a thought...


Didn't think you had Ethanol in Canada but wasn't 100% sure... I don't use it here but will probably have to some day...

 

[Miles Long]

Didn't think you had Ethanol in Canada but wasn't 100% sure... I don't use it here but will probably have to some day...[/QUOTE]

As of Jan 1st, all of our regular fuels "May contain up to 10% ethanol"
As far as I know, the premium grades are not spiked - yet.
This applies to New Brunswick. I'm not sure of the other provinces.
It's interesting to note that just prior to Jan 1st, a notice was circulated via Internet from a branch of the provincial government( I think it was the Dept. of Highways) advising all operators of gas-powered small equipment to use Hi-test gas in the equipment, if it to be stored for extended periods of time.
As for the "rough/surging idle" - I haven't had this problem as yet - but wouldn't this be a classic symptom of air leakage around a sealed surface, such as the carb boots? And the bike is an oldie as well.
Cheers, Miles

 

[Fastatv]

The popping or back firing is usually caused by a lean condition ( not saying that it could not be a low battery/electrical ) which is caused by too lean of an idle mixture, loose carb boot (s) meaning too much air, loose exhaust. Hope this helps.

 

[maleko89]

Sounds lean. Popping and hanging idle are clues.

 

[v-max 4]

Thanks for the advice guys. I’m not sure what to say about the possibility that all our regular grade fuels here in Ontario may contain up to 10 per cent ethanol. I was under the impression it was only those that advertised their ethanol content... but I must admit I don’t know for sure. I’m doubtful that’s the source of my problem but I’ll give the seafoam a try anyway... it can’t hurt.

I haven’t checked the voltage at idle recently but I went through the whole “electrical issues” thing a few years ago to correct the hot starting problem and brought the whole system up to snuff (which included a new upgraded reg/rect) so I’m assuming it’s all still good since the bike still cranks strong when it’s hot. But that’s also easy to re-check, so I will.

I realize it sounds like there’s a simple air leak somewhere in the intake but that was the first thing I checked for (a propane torch with the bike idling) with no luck. I will re-check the air pilot jet setting... I believe it should be 2 and a half turns out. I didn’t think about a loose exhaust so I’ll check into that one for sure and let you know the results.

 

[Shaner]

I have the same bike with the same issue. I know its not the gas or the throttle linkage. the diaphragms seem ok and snap back good. The bike starts up and warms up good then once it gets warm when you give it gas the rpms come down and get stuck on 3K. Tried lowering idle so its not that. idles at 1200 perfect then wont come back down after 3K. Ive cleaned the jets and carb ports before but its been a few years. Ive also recently synced the carbs. any tips would be great before I have to drag this beeotch to the mechanic. :ummm:

 

[lethal dose]

I'd check for vac leaks. A hanging idle is also indicative of this. Ask me how I know.

 

[Dragmaxster]

I have the same bike with the same issue. I know its not the gas or the throttle linkage. the diaphragms seem ok and snap back good. The bike starts up and warms up good then once it gets warm when you give it gas the rpms come down and get stuck on 3K. Tried lowering idle so its not that. idles at 1200 perfect then wont come back down after 3K. Ive cleaned the jets and carb ports before but its been a few years. Ive also recently synced the carbs. any tips would be great before I have to drag this beeotch to the mechanic. :ummm:

Try the shotgun and if that doesn't work then the peashooter.

 

[Woody]

when mine had idle issues. idle would be fine on the side stand.set the bike up to get on and idle went to 3000rpms. my (spelling) emulsion tube o rings had seen better days.
replaced them. no more issues.

 

[Dorney]

Thanks for the advice guys. I’m not sure what to say about the possibility that all our regular grade fuels here in Ontario may contain up to 10 per cent ethanol. I was under the impression it was only those that advertised their ethanol content... but I must admit I don’t know for sure. I’m doubtful that’s the source of my problem but I’ll give the seafoam a try anyway... it can’t hurt.

I haven’t checked the voltage at idle recently but I went through the whole “electrical issues” thing a few years ago to correct the hot starting problem and brought the whole system up to snuff (which included a new upgraded reg/rect) so I’m assuming it’s all still good since the bike still cranks strong when it’s hot. But that’s also easy to re-check, so I will.

I realize it sounds like there’s a simple air leak somewhere in the intake but that was the first thing I checked for (a propane torch with the bike idling) with no luck. I will re-check the air pilot jet setting... I believe it should be 2 and a half turns out. I didn’t think about a loose exhaust so I’ll check into that one for sure and let you know the results.

Did you check the 4 hose barb caps on the intakes ?

Dave