Gs1100g super rich

[chuck hahn]

Customers bike, Has stock jetting according to the parts fiches. Float heights are correct. Bike runs great on new plugs but quickly carbon fouls them and causes loss of cylinders. I have an add asking for good replacement needle jets.
So if i cant find needle jets my next thought was go down on the main jets in an effort to counter the holes in the needle jets being worn and allowing too much fuel through.
What are your thoughts on reducing main jet size??

 

[Nessism]

How many miles are on the bike? Unless it's north of 75,000 miles, it's hard to imagine that much wear on the needle jets.

 

[Rijko]

I bought a box of fake NGK plugs once.
They would become real sooty real quick .... and drop the cylinders.

So i put in 4 new ones, took me some time to figure out all 4 new plugs went bad ...
Are you sure they are proper plugs Chuck ?

 

[rphillips]

I'm no carb guru, but wear from fuel flowing through or across a brass part, enough to cause the problem you explain, just don't seem right... If running rich during normal riding, would it be reasonable to lower the needle a little, maybe more if as bad as you say.

 

[unfocused]

To set up a CV carb
Main jet first
Midrange
Low end
idle

If running pod filters you might need restrictors for the slide. Similar to the air correctors we run in the VM series of carbs when running pods.

http://www.factorypro.com/tech/tech_tuning_procedures/carbtun.html

For bikes over 8000 rpm redline ↓↓↓

http://www.factorypro.com/tech/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

I've followed the above with excellent results.

one thing I learned first hand... if you think you have a carb problem, check the ignition. In my case, I had both problems. Needed air correctors and a new ignition pickup... Now, I haven't needed to install air correctors in CV carbs as of yet. They're not as fickle as the VM carbs when installing aftermarket filters.

 

[Don R]

More than once I've found jets enlarged either on purpose or by enthusiastic cleaning with drills or torch tip cleaners. The number on the outside of the jet was left intact. Also, aftermarket jets can't be counted on to be correct.

 

[chuck hahn]

Stock pipes and airbox. He bought BR8ES from where i dont know. I put new out of the box coils on it that he had and put giming light on. timings dead on and no gaps in light pulses.
Runs perfect at higher RPMS but lower isnt so nice. And looking at parts fiches the needles are not adjustable.

 

[Nessism]

The needles can be adjusted, by changing the thickness of the shim stack on top of the needle clip. Thicker lowers the needle.

 

[salty_monk]

How about the enrichment valves? (choke). Could they be leaking and adding enough fuel to affect things? We know it's "a thing" because of the reports back from those who have used the services of our friend over in the UK to refurbish them.

I'd definitely try another set of plugs. Fake plugs are becoming "a thing" on Amazon / Ebay and even from some motor factors if the press is to be believed.
Good voltage at the coils I assume?

 

[chuck hahn]

ED wouldnt you make number 36 thinner?? The top one, number7, just centers the needle right?

https://www.partshark.com/oemparts/a/suz/50d40436f8700230d8b4ecf5/carburetor

 

[Nessism]

ED wouldnt you make number 36 thinner?? The top one, number7, just centers the needle right?

no. read my tutorial

 

[rphillips]

Chuck, this is a different adj. than I've ever made. We were always raising the needle a little for a little more fuel. I never remember anybody wanting to lower them. It'll be interesting to see how this works out, and what you finally find... Good luck

 

[chuck hahn]

Read your tutorial Where?? Bikecliffs??

 

[salty_monk]

https://gsarchive.bwringer.com/mtsac/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf

 

[chuck hahn]

Kid brought the bike over and based on that he told me "everythings new according to the service manuaks OEM specs" I put the colortunes in and observed the flame colors in each hole. Above 3000 RPM all were bunson burner blue as the should be. At idle they were orange yellow indicating rich. Adjusted the mixture IN till it leaned them out. I again questioned him if the rubber pilot jet plugs are new or not. He admitted that he didnt replace them when he pt it back to stock jetting when he took the 4 into 1 off and put stock pipes on. I handed him 4 new ones and told him to push them in real tight when replacing them. Texted me last night and no more sooty fouled plugs. So it seems i bit and came to the assumption that if EVERYTHINGS NEW the only variable would be worn out holes in the needle jets. My mouth has heeled from taking the hook out..lol

 

[Don R]

Thanks for posting the resolution, we can all learn from these posts.