Gs 850 Popping On Deceleration Need Help Please!

[jimfj]

Hello all,

1982 GS 850G
17000 miles
Sitting for a while bringing her back to running condition.
Finished so far:
Valve adjustment
Carb cleaning and o ring replacement
Carb boot o rings
Checked petcock (functioning properly)
Oil change and filter

The bike will start right away from cold with choke. Idles up for a very short time and then comes down to 1000 or so. Idles okay, I think #1 is not getting hot right away. ( from squirting pipe with water)

After warm up it will run pretty well although I have alot of popping on deceleration. I also think there is more power there but problem with the popping is holding it up.

At a constant or cruising speed, say 3000-3500 rpm i hear a little flutter in the exhaust, nothing terrible, but the enigine is not rock solid consistant.

Basically I'm at the point where it ridable, it stays running, doesn't die, has power, but I know the popping is a clue that there is still something wrong.

Please advise as to what I should do next. I appreciate all suggestions. This is not an easy thing to figure out and the more things I can eliminate the quicker i can really enjoy the bike.

Jim

 

[chuckycheese]

Lean

Lean

I don't think you probably have much of a problem. How do your plugs look? It sounds like it's running a bit lean. Take a look at your plugs and you may find that backing out your air mixture screws 1/4 or 1/2 turn will put a smile on your face!\\/Judge each cylinder separately and don't over do it if you make adjustments....it often takes very little.

 

[rustybronco]

Basically I'm at the point where it ridable, it stays running, doesn't die, has power, but I know the popping is a clue that there is still something wrong.

Please advise as to what I should do next. I appreciate all suggestions. This is not an easy thing to figure out and the more things I can eliminate the quicker i can really enjoy the bike.
Jim

Is the air box properly sealed up? <hint> side cover weather strips...

 

[Roostabunny]

I'll second "check the airbox".

You're looking for an airtight seal on both side covers and between the filter and it's mounting surface.

Here are the pics I took while fixing up mine http://picasaweb.google.com/roostabunny/GS850AirboxFixup - apparently it's a rite of passage on the 850's.

This process took care of my popping (air leaks were creating a lean condition). Your airbox may be fine, but it's common for those side cover seals to be shredded and the airbox boots to be hard and shrunken.

 

[jimfj]

The airbox is one thing that I haven't spent any time on.

I looked at the air filter once and I put it on the list to replace but haven't done it yet. I'm sure the seals need help just from looking at the condition of other things on the bike.

My bike has the electronic ignition (no points). Do I need to check the timing at all?

Jim

 

[rustybronco]

The airbox is one thing that I haven't spent any time on.

My bike has the electronic ignition (no points). Do I need to check the timing at all?

Jim

Not at this point, but maybe in the future. (haven't ever checked mine)

 

[mortation]

I have been battling this issue since I got my bike running over a year ago. It is very minimal now but still driving me nuts. I may need to try a re-sync and adjusting of the carbs after this last batch of maintenance.

Anyway here is the list of things I have done that you may want to check.

1) Rebuilt airbox to make sure it was fully sealed, including new airbox boots
2) Replaced exhaust gaskets
3) New carb engine side boots
4) New Coils, Plugs, wires, and caps
5) Valve Adjustment
6) Tuned carbs w/ mano meter and color tune
7) rebuilt carbs

I am going to re-tune my carbs soon and if that doesnt solve the problem only thing I can think of is the cam timing being slightly off or a valve issue even though compression is fine.

Good luck and keep me posted if you figure out your issue

 

[jimfj]

Did replaceing the coils, wires and caps help anything? My wires are okay as far as I know but just wondering?


Jim

 

[mortation]

Did replaceing the coils, wires and caps help anything? My wires are okay as far as I know but just wondering?


Jim

The bike is running very well. The issues you are having I had pretty bad too before I did the above mentioned things, now its very rare/faint but still happens. Unfortunately I did most of them at the same times I can't really tell which part of those actions made it better.

Did you check for vacume leaks on your boots? Air box sealed? Exhaust holes?

 

[Roostabunny]

The airbox is one thing that I haven't spent any time on.

I looked at the air filter once and I put it on the list to replace but haven't done it yet. I'm sure the seals need help just from looking at the condition of other things on the bike.

My bike has the electronic ignition (no points). Do I need to check the timing at all?

Jim

I've never checked my timing either. The shop manual describes the electronic ignitions as "maintenance free", and the only procedures listed are tests to see if the electronic parts are bad. In my reading around here problems with electronic ignition are rare.

There are much more qualified carb experts than me floating around here, but given that you're just getting it running after a long "rest" I'm going with popping means a lean mixture, and your first point of attack should be air leaks. If you don't plug the air leaks, nothing else you do about your mixture will matter and you will go batty.

 

[spyug]

Popping on decelaration is classic symptom of air leak or more correctly, air infiltration causing excessively lean running. As mentioned, the airbox might not be tightly sealed or you could have a split or crack in one of the boots to the carb. You could also have a split or cracked o-ring in the carb assembly or even in the carb manifolds. You need to check these all out.

I'd start at the airbox as this is often the source of the problems. It seems that GSs don't like to run properly with out the airbox being properly sealed.Check the airbox to carbs next. If and when they get hard they can split and or may not seal tightly at the carb. A change out might be required.

The carbs themselves can also be a big problem with all the o-rings that can split or crack with age. If they haven't been rebuilt in a while it might be smart to do a clean and rebuild. Our buddy Robt. Barr at cyclorings is the source for these parts. Excellent, hi speed service.

Less frequently than the foregoing, the carb manifolds can split and crack allowing air in so once you have the carbs off, give them a clean and a good eyeballing for deterioration.

Don't worry about timing and valve clearances at this point. you need to home in on too much air going in and leaning out your mixture.

Good luck with this.
Cheers,
Spyug.

 

[jimfj]

I appreciate what all of you have said.

Here is what I found when removing the airbox.

The side seals are crumbling and gone. The seal on the top of the filter element that fits to the airbox is gone too. The air filter element is trashed and crumbling.

Can I buy just the foam element for the filter or do I have to buy the whole thing including the squirrel cage? These things are stupid expensive!


Jim

 

[mortation]

I appreciate what all of you have said.

Here is what I found when removing the airbox.

The side seals are crumbling and gone. The seal on the top of the filter element that fits to the airbox is gone too. The air filter element is trashed and crumbling.

Can I buy just the foam element for the filter or do I have to buy the whole thing including the squirrel cage? These things are stupid expensive!


Jim

I think from the dealer it is all one piece. I got mine all new. you may be able to get a foam insert from eBay and redo the seals with weather stripping but I have never done it.

 

[seuadr]

I think from the dealer it is all one piece. I got mine all new. you may be able to get a foam insert from eBay and redo the seals with weather stripping but I have never done it.

you can easily redo the seals with weatherstripping and replace the filter foam part. go to your local bike or auto parts store and pick up a sheet of uni filter material. you can cut it to size and shape and either glue it together, staple it, or melt it and stick it together.

 

[rustybronco]

I appreciate what all of you have said.
Can I buy just the foam element for the filter or do I have to buy the whole thing including the squirrel cage? These things are stupid expensive!
Jim

Buy a k&n filter and reuse the cage.
http://i32.photobucket.com/albums/d44/rustybronco/PICT2046.jpg
http://i32.photobucket.com/albums/d44/rustybronco/PICT2048.jpg

 

[Roostabunny]

I appreciate what all of you have said.

Here is what I found when removing the airbox.

The side seals are crumbling and gone. The seal on the top of the filter element that fits to the airbox is gone too. The air filter element is trashed and crumbling.

Can I buy just the foam element for the filter or do I have to buy the whole thing including the squirrel cage? These things are stupid expensive!


Jim

I think you can get just the foam element for your filter but I don't have a source off-hand. I'd think BikeBandit or Z1 or Flatout would have them. Buy a spray can of filter oil while you're at it - as fussy as these bikes are about intake, over and under-oiling the filter can mess you up as well.

Meantime, I fixed both the disintegrated foam seal on top of the filter and the side seals with $4 worth of weather stripping from Ace Hardware. The filter seal I just scraped off the housing (tight fit for your hand) and I fixed the replacement weatherstripping directly to the filter rather than trying to get a good flat adhesive seal inside the airbox. Muuuuch easier, given the tight quarters. See my pics for a little detail.

Others have had success replacing the side seals using silicone caulk and plastic wrap as a release film. If you can't re-use the top part of your side seal as I did, the silicone method might be easier. Never tried it though.

Also, when you have the airbox apart, make sure to clean out the narrow space at the top of the inside of the box. It leads to the breather hose fitting. It's real narrow - a 12" or so piece of wire from a coat hanger, with the final inch bent at a 90? angle works like a charm to "rake" the rust gunk out of there.

Welcome to the 850 club, and good luck.

 

[bwringer]

Decel popping is also a classic sign of exhaust leaks, too.

If you've had the exhaust off, did you replace the gaskets between the pipes and the cylinder head? Did you get the old ones out completely out? Any rust holes?

There are also a couple of places underneath where the pieces of the exhaust are clamped together. The sealing "sleeves" between these might be damaged.

And please, check the valve clearances ASAP.

 

[jimfj]

ARRRRG!

I sealed the airbox completely and replaced the foam on the airfilter. Homemade job but it fits the bill. I rechecked everything,
Carb boots --okay
air box boots--Okay
air box sealed--done
new plugs--done
Carb adjust, each needle turned out or loosened to get more flow and still she pops on deceleration...not as bad but its still there.

Where do I go from here?

I haven't checked the exhaust other than a visual inspection and it looks to be fine. My GS425 didn't have any gaskets between the pipes and the head. It just had the 2 little sleeves.

As always help is appreciated.

Jim

 

[chuckycheese]

Plugs?

Plugs?

I was the first one to respond to your post and asked about your plugs. I know they're new but what do they look like? You've never mentioned that.

Personally, I think air leaks are overrated, rarely found and not often the problem. I base that opinion on anecdotal information here on the forum and personal experience. I've had leaks that caused no problems and have experimented with loosening up boots to see if I could cause a problem. I'm sure leaks can be a problem, for certain, but I don't think they usually are.

If you do a search, you'll find air leaks blamed for something every day but when people follow-up with their solutions, it's usually a carb problem.:-s

 

[rustybronco]

Based on my personal experience, the air box seals made a big difference as did putting the air filter back in correctly. the plus side is, now you know they are done and eliminated from the equation.
one thing I would add to what was said, when you go through the carbs, be sure that you look through all the jets, emulsion tubes, seats and make sure they are CLEAN. I use a jewelers eye loop, no need to do the carbs twice!

***check jets sizes***