Off-idle stumble

[MtnMan]

I replaced the fuel filter and pulled the vacuum line off of carb #3, plugged the connection at the carb and did not notice any change.

Things point to the carburetors as the bike runs very well at medium and wide throttle openings. I am still looking into new coils and plug wires.

If this does not help I will take the carbs off and replace the jets, see if the slides stick.

Thanks again guys for all your help, I will have more questions!

Armin

 

[bbells]

I just went through this with my bike. I am not sure if what worked for me will work for you. I think the stumble is usually a sign of a slightly lean mixture.
1) How much seafoam did you put in it? You need to add about 1/2 a can per tank. It took 2 tanks to clear up my bike. And, the stumble was worse while the seafoam was in the bike.
2) Have you adjusted the valves? I learned the hard way that my bike likes the go/no go way of using the feeler gauge.
3) A very careful synching of the carbs helped.
4) I removed the stock fuel filter and replaced it with a generic one. I think crud in the tank may have been clogging up the original - And I though spending $2 was more attractive than the cost of a Honda filter.
Off all these things, the 2 tanks with 1/2 can of seafoam in them helped the most, was the least invasive, and the least expensive in time and money.
Good luck! If it doesn't clear up I would start with cleaning the carbs and moving on from there. You don't say where you are, but if you are in the Minneapolis area Bruno's will clean your carbs for $200 plus the cost of any parts that may be needed.

 

[MtnMan]

Thank you for your suggestions!

1) How much seafoam did you put in it? --> About 1/2 a can. Interesting that the stumble was worse with the seafoam.

2) Have you adjusted the valves? --> No, but very soon I will.

3) A very careful synching of the carbs helped. --> I will sync again.

4) I removed the stock fuel filter and replaced it with a generic one. --> I did this.

Cleaning the carbs: the previous owner said he cleaned the carbs, but he did not replace any jets. I live in the Boulder/Denver area.

I plan to look at the carb slides to see if they moove freely.

Armin

 

[MtnMan]

Here is what Z1 Enterprises recommends for the GL1100:

"The DC1-1 coils are a good choice for the GL models. https://www.z1enterprises.com/detail.aspx?ID=210.

If you use some sort of electronic device, ie. Radio, gps system, etc. choose one of the suppression core wire sets. DW500, DW600 or DW800. Otherwise, one of the copper core wire sets DW200 or DW300 are fine."

Any comments on the coils?

I have to look up what the differences are between DW500, DW600 and DW800.

Armin

 

[joedrum]

hmmmmm the 1100s and dyna green coils are not the perfect match but id say it will do fine and better than stock....

 

[MtnMan]

hmmmmm the 1100s and dyna green coils are not the perfect match but id say it will do fine and better than stock....

I'm looking for the best match...

What is your recommendation?

Thank you,
Armin

 

[joedrum]

it seems to be the the greatess secret ever ....ive been seaching this deal forever it seems ....80-81 1100s have different resistance than 82-83 dose ....both are under 3ohms ....id say you have made a good choice the dyna coils are a great product ...just get the wire too ....and i think it will be good my opinion ...for sure no damage to anything

 

[MtnMan]

I just returned from a nice 3 hour ride in the mountains. My 1981 GL1100 still has the off-idle stumble but other than that it runs very well.

About 150 ft. before I arrived at my home I stopped at a stop sign and the engine almost died.

I had to give it some throttle to keep it running. When I arrived I got off the throttle and the idle speed dropped to ~500 rpm.
Normally - and absolutely reliably - the bike idles at ~1,000 rpm. The gas tank is full...

How could this happen all of a sudden? :headscratch: I don't think it is directly related to the off-idle stumble. The bike has always been idling fine and started easily.

To address the off-idle stumble I am planning to rebuild a set of 1983 GL1100 carbs. Are they 100% compatible with my 1981?

Any advice would be appreciated!

Armin

 

[slabghost]

Check your vacuum advance. If it leaks you are likely drawing in too much air to run. I'm putting mine together now after replacing a blown vacuum advance.

 

[joedrum]

yes slabs right if the vacume canister is bad its a strait vacume leak on the carbs ....the 83 carbs are completely compatible but i think your off idle problem could just be a vacume leak only...you can plug the hose from carb to canister and see if that changes it greatly

 

[MtnMan]

yes slabs right if the vacume canister is bad its a strait vacume leak on the carbs ....the 83 carbs are completely compatible but i think your off idle problem could just be a vacume leak only...you can plug the hose from carb to canister and see if that changes it greatly

Thank you, I pulled the vacuum line off of carb #3, plugged the connection at the carb and did not notice any change.

I am still puzzled why all of a sudden the idle speed dropped so much.

Armin

 

[dan filipi]

It could be one carb has started flooding causing it to run rich which will lower the idle, or one carb too lean could also lower the idle.
I'd pull the air filter out and look down into the carbs to see if there's any raw gas in it.
That's a telltale sign of fuel level being too high.

Also, if it's running good otherwise I'd bump the idle up to 1000 then see how it goes and add 8 oz. of atf to a tank then put miles on it. The atf will clean things up.

 

[slabghost]

Could be you just got some bad gas lately too.

 

[petefan1]

I think the clue is there...the off idle stumble. plugged port(s) somewhere.

 

[MtnMan]

I think the clue is there...the off idle stumble. plugged port(s) somewhere.

Maybe some "crud" got dislodged?

 

[MtnMan]

It could be one carb has started flooding causing it to run rich which will lower the idle, or one carb too lean could also lower the idle.
I'd pull the air filter out and look down into the carbs to see if there's any raw gas in it.
That's a telltale sign of fuel level being too high.

Also, if it's running good otherwise I'd bump the idle up to 1000 then see how it goes and add 8 oz. of atf to a tank then put miles on it. The atf will clean things up.

I pulled the air filter and did not see any raw gas and also did not detect a whole lot of gas odor.

I am still wondering why the idle drop was so sudden at the end of a longer ride. Maybe something got dislodged and clogged a passage or jet downstream?

Thanks for all your help!
Armin

 

[joedrum]

well ive had things like this go up and down on idle before ...ive never thought to much about it ...but it seems these problems happen to 1000 style carbs and 1100 carbs or 1200 carbs ...on the 1100 s they have excellerator pump that might be bad ...

also it could weak spark ...oldwings with weak spark cause all kinds of carb trouble that isnt carbs trouble at all ..kinda looking like this also....at idle and just above idle is the weakest spark that happens...

 

[slabghost]

Yes low voltage + lost voltage through old connections and switches makes for very weak spark.

 

[dinorider]

im having a very similar problem with my '80 1100. guess i will take a look at vaccum lines tomorrow. seafoam hasnt done a thing for it. of course i am running the mixture a bit heavier than you guys suggest. run her dry, dump in a full can and fill her up. she wont idle at all or she idles at about 3k. either way, it aint right. getting a lot of rattle at lower rpm also, it has done this since i got it, and i have only put about 400 miles on her so far. only had her for less than a week. sure wish this thing ran as good as my '78.

 

[MtnMan]

Well, after replacing the plug wires and adjusting the valves with no effect I finally removed the carbs.

After draining them, I turned them over to remove the float bowls and heard a faint rattling noise. I opened the first float bowl and saw a #145 main jet IN the bowl, "floating around"!

In hindsight it is surprising how well the bike ran with only 3 main jets.

I will thoroughly clean the carbs and rebuild them. I may have to ask a few installation questions along the way, still wondering how I will install the throttle cables with so little space! :Awe:

Thanks again for all your help!

Armin