GS650G Bogs,Sputters and Pops

[kruzin]

Hi, I'm trying to bring back this bike from dead and have it looking great and running but at around 6000 rpm its starts to bog sputter and pops out the exhaust the pop isnt quite a backfire also when cold and on choke there isnt a fast cold idle i have gone through the cards twice syncronized them (19in of vacuum at 1000 rpm)at 3000 rpm all were pretty equal i have cleaned the fuel tank installed a inline fuel filter and a new pet cock this is an 1982 gs650g shaft drive it had a 4-1 header on it and filter pods when i got it so im running with that im not sure if any engine mods other then that have been done could it be the wrong sized jets for running with the header and pods?i believe the jets had #150 on them and the needle is on the 2nd clip position air screws are turned out 2 turns any help on this would be great. thanx

[Dave8338]

Hi, I'm trying to bring back this bike from dead and have it looking great and running but at around 6000 rpm its starts to bog sputter and pops out the exhaust the pop isnt quite a backfire also when cold and on choke there isnt a fast cold idle i have gone through the cards twice syncronized them (19in of vacuum at 1000 rpm)at 3000 rpm all were pretty equal i have cleaned the fuel tank installed a inline fuel filter and a new pet cock this is an 1982 gs650g shaft drive it had a 4-1 header on it and filter pods when i got it so im running with that im not sure if any engine mods other then that have been done could it be the wrong sized jets for running with the header and pods?i believe the jets had #150 on them and the needle is on the 2nd clip position air screws are turned out 2 turns any help on this would be great. thanx

Sounds lean on the mains or very top end of the pilots... Have you checked where the needles are set on the slides? I had to raise mine just slightly (1/2 notch) to get things to pull perfectly and it is a completely stock bike. I myself would also suspect the inline filter, I'm not a real big fan of a double filter setup (think fuel restrictions = lean) and you may well be running out of flow when hitting the 6k mark.

I think that the 150's may be a little small for pods and a 4-1 but others will have a better idea on that combo/set-up.

Welcome to the fourm and there will several others along shortly to give you some more advice...

[tkent02]

also when cold and on choke there isnt a fast cold idle

Did you clear out the choke feed passage in the float bowl itself?

i believe the jets had #150 on them and the needle is on the 2nd clip position

Dyno Jet or Mikuni main jets?
If there are clip positions someone has swapped needles. Second from top or from bottom?
Those 150s sound huge either way if you are referring to the main jets, but I don't really know about the 650s.
Are the plugs black or white after running it wide open for a while?

air screws are turned out 2 turns any help on this would be great. thanx

How did you come up with two turns out on the mixture screws?

[kruzin]

Did you clear out the choke feed passage in the float bowl itself? yes fully disassembled and cleaned choke plungers and all passages in the carb bodies





Dyno Jet or Mikuni main jets?
If there are clip positions someone has swapped needles. Second from top or from bottom?
Those 150s sound huge either way if you are referring to the main jets, but I don't really know about the 650s.
Are the plugs black or white after running it wide open for a while?

they are 2nd from the bottom some may have changed the needle but look to be original mikuni type dont know anything about the history of the bike it was a barn find the plugs are a gray color now since i put new plugs in it #4 was gas fouled prior to the change





How did you come up with two turns out on the mixture screws?

2 turns got me a good idle i found a chart in a previous post that showed 1.5 turns as being the factory setting

[KitKat]

i had sort of a similar problem. And my problem included that when i turned electrical stuff on (high beam, turn signals) it would be fine. = r/r problem. Got an r/r from duanage, and was perfect

[waterman]

I question the need for 150 mains, stock for this bike is 110. It does sound like it may have a dynojet kit installed since the adjustable needle. Either way, I would suggest some plug chops to verify mixture conditions.

Is the fuel filter allowing enough flow for demand? I would try to run without filter to rule this out.

How are the Orings on the intake boots, when was your last valve adjustment, and are your pods over oiled? So many questions, but all could be causing your troubles.