question about running lean

[Guest]

Would running lean cause a slight popping noise similar to when there is a cylinder missing?

I have the popping noise when idleing and when cruising at a steady speed with the engine running over 3500 rpm.

The bike is an 82 gs1100gl and as far as I know the carbs and exhaust are stock. So far I have sealed the air box, replaced the air filter and the intake boot o-rings. The rubber boots for both sides are not in the budget right now. The ones on there are slightly pliable and fit snugly on the carbs though. My carbs still have the plugs over the mixture screws, it is my understanding that there is an o-ring in with the mixture screw. Is it possible the o-ring here is bad and letting in the air making me lean?

Thanks for all the help folks.

[Hoges]

I think with running lean you get the popping out of the exhaust due to unburnt fuel gases igniting. It does happen when you back off normally, as mine is doing it now and am playing around with it.

[chef1366]

Could be dirty carbs
A lean condition
And as stated ^a rich condition.
I would start by pulling the carbs and cleaning them.

http://www.thegsresources.com/gs_carbrebuild.htm

[GQROD]

1-Check your plug gap and color, this will tell you if you are lean or rich. The gap may be off slightly leading in part to this.

2-Make sure your carbs are meticulously clean, ie: pilot air jets and pilot jets, as well as your slow circuit or starter circuit.

3-Make sure your mixture is correct using a color tune if possible, this allows for a more precise mix to each cylinder.

4-Sync your carbs to have even air flow or vacuum between cylinders.

hope this helps get you in the right direction.

[Suzuki mad]

A little help from your friends??

I have the popping noise when idleing and when cruising at a steady speed with the engine running over 3500 rpm.

The bike is an 82 gs1100gl and as far as I know the carbs and exhaust are stock. So far I have sealed the air box, replaced the air filter and the intake boot o-rings. The rubber boots for both sides are not in the budget right now.

What did you seal the air box with??

A 1982 GS with stock carbs and exhaust I can handle but you have had the carbs off to change the O rings. How long were they off the bike? Whats the bike history e.g. How long have you had it, has it stood for a while, is this how you bought the bike?

These will help people give a better answer to your problem.

Suzuki mad

[dr_fosg8]

The plugs are all showing a lean condition, white insulators with light grey electrodes. I can post some pics of them tonight if it would help. Also checked the gaps last night and those were all in spec.

The carbs were pulled and cleaned 2 times so far by me, but the o-rings were not changed.

I have had the bike about 1.5 months and it would only run with the choke on when I got it. Carbs were very dirty. The P/O had said it was sitting 9 years when I bought it.

The air box was sealed the same as showed in another post from this site with the rubber weather stripping.

[Nessism]

To properly clean the carbs you have to ungang them and soak them in carb dip. Since the dip will attack all rubber parts, you need to pull those pilot screw caps and remove the screws. The pilot circuit in particular has some really small orifices involved so making sure they are fully open is critical to making the bike function as designed. Keep in mind that we are talking about a 26 year old motorcycle here and the rubber parts soaking in gasoline just plain don't last that long. Another critical thing is making sure the valves are adjusted properly. For some reason many GS owners don't do this which can cause all kinds of odd running issues.

Good luck.

[Suzuki mad]

Carbs again......

The plugs are all showing a lean condition, white insulators with light grey electrodes. I can post some pics of them tonight if it would help. Also checked the gaps last night and those were all in spec.

Sounds like running lean, a carb or airbox problem.

The carbs were pulled and cleaned 2 times so far by me, but the o-rings were not changed.

I have had the bike about 1.5 months and it would only run with the choke on when I got it. Carbs were very dirty. The P/O had said it was sitting 9 years when I bought it.

You need to 'pull' the carbs again and clean the as per the instruction on carb cleaning. These do work as I didn't pull the air screws and had problems. Once followed my GS ran like a dream.

Thats part of why the PO sold the bike. You have to think what else is wrong with the bike for being off the road for 9 years. You've possibly got a blocked passage on a couple or all the pilot jets circuits.

The air box was sealed the same as showed in another post from this site with the rubber weather stripping.

You can get the rubber seals for the airbox for the later 1100 (bought some this year in the UK) which would save the use of rubber stripping. This could also be an area of problems with the bike running lean.

You don't know why the bike was sold originally. Your guessing as to what is wrong with it other than it won't run other than on choke and now its runs lean. What you are doing is helping but not curing the problem. If you work sytematically through the carbs and airbox/inlet area then you know that its done.

Suzuki mad

[dr_fosg8]

Thanks for the tips folks!

Nessism. The valves were checked and corrected, I had three of them with less than allowable clearance.

Also went and picked up a gallon of the carb/parts cleaner to dip the carbs in and the first one is soaking. I will be getting the o-ring kit from Mr. Barr ordered up here soon.

When the carbs are reassembled how do you adjust the mixture screws? Screw them all the way in them back them out? 2 - 2.5 turns correct? What does the screw alter? Air or fuel?

Will report back when the soaking is completed.

[Nessism]

Good job on doing the carbs right.

The mixture screw allows a emulsion of gas and air to enter the airflow just downstream of the butterfly. The farther the pilot screw is out, the richer the idle mixture will be. 2.5 turns out is a good starting point for most GS's. After you get the bike running again set the screws so the highest idle speed is achieved. If you can't tell any difference when tweaking the screws, just make sure they are all set the same number of turns. Oh, and don't forget to do a vacuum carb sync.

Good luck, the fun never stops!

[silverhorse47]

How hot is the bike when it is backfiring? Is it backfiring out the carbs, or out the exhaust? The colour of the plugs tells you it is running lean. You either have an airleak, or your carbs need work. Have you tried adjusting the needles?

S.

[dr_fosg8]

Carbs back on

Silverhorse: The light backfire comes from the exhaust when it is fully hot. Ie after coming home from work (16 mile highway trip).

The carbs are dipped and blown out with compressed air reassembled with new o-rings ( A VERY big thank you to Mr. Robert Barr ). All of my mixture screws were around 2 turns out when taken apart, I set them 2.5 out when reassembled.

First off let me say for those who don't think that dipping is necessary, IT IS. I myself didn't think so until now. The crap that came off into the dip was unbelievable, and I cleaned the outsides before putting them in.

Now on to the results. Took the bike for a ride and it runs much smoother and pulls like WOW! Almost no hesitation from cruising at 60 to WOT. All in all a much stronger running engine, but...I know always a but. I still show that I am running lean on the plugs. They are not the stark white they were before they seem to be a VERY light tan with dark brown little specs. My electrodes are brown though. Is this what I want?

Sorry if it a elementary question but the pics of plugs in the clymers are B/W and it has been at least 14 years since I looked at plugs, and even then it was on a 2-stroke.

Thanks for all the help and suggestions.

[J_C]

A light tan is right around where you should have it. Do you have any popping now when idling or on deceleration?

[silverhorse47]

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html