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Discussion Starter · #1 ·
So Ihave a 1981 GS850GL, pod filters (Mikes XS) and chopped exhaust. Cylinders 1,2, and 4 are running very lean while cylinder 3 runs perfect. All the jetting is the same (dynojet kit). Tried adjusting needles and still nothing. And suggestions on what to do? No leaks in boots as they have just been replaced. Bike bogs after about half throttle in 3rd up to 5th. Also running an electronic ignition no points.
 

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So Ihave a 1981 GS850GL, pod filters (Mikes XS) and chopped exhaust.
Does it run better after warming up.......or if you apply a little choke ?

Putting the intake and exhaust back to stock.......or near to......likely will solve your problem.
Honestly.
And your bike will be less obnoxious too.

A double dose of Berrymans B12 Chemtool in the gas might help too, along with running until hot a few times over a couple of days.

Regardless of whatever else helps your problem, please consider putting something at least resembling a muffle back on it. Your ears will thank you.
 

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Discussion Starter · #3 ·
Does it run better after warming up.......or if you apply a little choke ?

Putting the intake and exhaust back to stock.......or near to......likely will solve your problem.
Honestly.
And your bike will be less obnoxious too.

A double dose of Berrymans B12 Chemtool in the gas might help too, along with running until hot a few times over a couple of days.

Regardless of whatever else helps your problem, please consider putting something at least resembling a muffle back on it. Your ears will thank you.
Started to put lolipops on 9ne side of the exhaust to test if that helps at all. Already reinstalled stock airbox with next to no improvement. Bike starts and runs fine just hot and obviously lean. Thanks for the suggestion!
 

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Already reinstalled stock airbox with next to no improvement.
It is the stock air FILTER that is important.
And how do you know it is "obviously lean" ?

Shorty pipes are almost always single wall and stock ones often are double.
That alone makes the PIPES hotter.......but does not necessarily mean the engine is.
 

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you should put the mikuni needle and jets back in. when it bogs at half throttle have you tried appling choke to see if it gets better. ethinol in the gas causes the plugs to be white, do they look burnt? you can buy mikuni jets anywhere for less than $10.00
 

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Discussion Starter · #6 ·
It is the stock air FILTER that is important.
And how do you know it is "obviously lean" ?

Shorty pipes are almost always single wall and stock ones often are double.
That alone makes the PIPES hotter.......but does not necessarily mean the engine is.
Well the plugs are pure white with no buildup, I returned everything back to stock including jetting, needles, filter, and exhaust. The problem is still there. Still lots of sputtering and afterfire. Starting to think this may be a head gasket problem as I did notice a small amount of oil on the base of the head.
 

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Discussion Starter · #7 ·
you should put the mikuni needle and jets back in. when it bogs at half throttle have you tried appling choke to see if it gets better. ethinol in the gas causes the plugs to be white, do they look burnt? you can buy mikuni jets anywhere for less than $10.00
I did try returning everything to stock, choke has very little effect virtually none. The plugs are white and very hot, 2 of them actually started bending closing the gap. Possible head gasket problem? I'm running out of solutions have no clue what else it could be.
 

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Back about 5 posts ago, I recommended using some GOOD carb cleaner to get at the tiny little low speed passages in the carbs that are hard to clean manually AND are mostly unaffected by changing out the "jets".
THIS IS YOUR CLUE AS TO WHAT ELSE IT COULD BE.
Second edition.
Also could be a vacuum leak somewhere around the intake.
 

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Discussion Starter · #9 ·
Back about 5 posts ago, I recommended using some GOOD carb cleaner to get at the tiny little low speed passages in the carbs that are hard to clean manually AND are mostly unaffected by changing out the "jets".
THIS IS YOUR CLUE AS TO WHAT ELSE IT COULD BE.
Second edition.
Also could be a vacuum leak somewhere around the intake.
The carbs were totally cleaned with carb cleaner, an ultrasonic cleaner, then the air compressor. So I don't believe there are any clogs or debris. I did take a compression test had had numbers around 70-80 on the three cylinders while the other was in the neighborhood of 130. Poured oil down the cylinders with no improvement. Could a faulty head gasket be allowing this type of vacuum leak?
 

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Took the head of and its definitely the head gasket, burnt up and cracked.
OK, that's half the battle.
In order to fix that right, the head AND the cylinder block both need to be checked to be sure neither is warped BEFORE you put it back together with a new gasket.
 
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