B12 Problem (carburetors?)

[ptitza]

Recently I've encountered strange problem. Anytime I cruise at relatively low speeds(and RPM's) I hear and feel stumbling. I've cleaned,re-adjusted and re-balanced carbs, changed plugs,cleaned the air filter(K&N).
Acceleration is smooth.
What could it possibly be?

[snofrog]

are you running a jet kit of any kind or is your jetting stock?

[ptitza]

are you running a jet kit of any kind or is your jetting stock?

Dynojet stage 1

[solman]

Dynojet, hmmmm.   Could be a carb sync, or your jetting may be off.

[ptitza]

Dynojet, hmmmm.   Could be a carb sync, or your jetting may be off.

I've synced the carbs, no effect.
And mis-jetting cannot happen overnight.
Actually, I'm beginning to suspect CDI unit.
The only problem is getting replacement one to test.

[snofrog]

could this be a situation where your airfilter was dirty when you installed/calibrated the jet kit and now with a clean filter you are lean on the bottom ,btw sounds like a classic lean out to me .if you have an inductive timing light you could hook it up to make sure you are consistently sparking through the rough area by watching the light (no ...dont point it at your face ) lol

[solman]

Also try new spark plugs.  I've had issues twice on the B12 and once on a CB750 where it turned out to be spark plugs gone bad or spark plug wires.  I kept chasing carb problems and it turned out to be a spark issue.

[ptitza]

could this be a situation where your airfilter was dirty when you installed/calibrated the jet kit and now with a clean filter you are lean on the bottom ,btw sounds like a classic lean out to me .if you have an inductive timing light you could hook it up to make sure you are consistently sparking through the rough area by watching the light (no ...dont point it at your face ) lol

Jet kit was installed smth. like 40k miles ago(bike has around 60 on the clock in total).
Never had any problems since the installation(and did sync-cleaning-etc. numerous times since that).
Problems like mis-jetting cannot happen 40k miles after jet kit installation.

[ptitza]

Also try new spark plugs.  I've had issues twice on the B12 and once on a CB750 where it turned out to be spark plugs gone bad or spark plug wires.  I kept chasing carb problems and it turned out to be a spark issue.

Already done that. No change.

[snofrog]

Problems like mis-jetting cannot happen 40k miles after jet kit installation.

that is very true ,however that is info that only you have untill such time as you decide to release it...I`m just trying to help with the info that I have to go on at the time  C-YA

[ptitza]

Problems like mis-jetting cannot happen 40k miles after jet kit installation.

that is very true ,however that is info that only you have untill such time as you decide to release it...I`m just trying to help with the info that I have to go on at the time  C-YA

Sure thing, but I would have started the thread with "I've recently installed jet kit" otherwise:)

[Daytona]

="ptitza"]Jet kit was installed smth. like 40k miles ago(bike has around 60 on the clock in total).Never had any problems since the installation(and did sync-cleaning-etc. numerous times since that).
Problems like mis-jetting cannot happen 40k miles after jet kit installation.

60k of trouble free miles!!!  That's a Bandit... What RPM? You say low?? Can you read the plugs? low rpm's like that is easy to do! Ride it to your home spot doing what it does! Kill the switch pull a plug and read it! Sooty could be your emulsion tubes are ovaled at the bottom end! Allowing more fuel at about midrange when the slides just start to lift. Common on mid age Bandit 1200 of which there are many!!    

[Daytona]

Hey "ptitza" since you don't give me much help on what you have or where you are! anyone tryin to help has to guess even at guessing what is the problem!!! I see you have had probs in the past!!! Don't have a magic pill for you on this! What did you do with the poor mpg? Thinking enough of this site and taking the time to post after you get it fixed would help in the future! you and others. Now back to your prob, i found that going to a diff plug, Walmart 8809 champions, about $2.50 ea gets the kernal into the main stream of chamber, is a bit hotter, cut out most of the steady low speed surgy stuff my 1GB12 had. But i'm @ sea level stock jets, slide pins shimmed .005, pilots out to almost 3 turns, bolt on Yoshi Race, 6, 3/16 holes drilled in R-side of air box, Uni foam filter. 16x43 sprockets. 45 mpg.... You sound like you can do most of your own stuff so i'm not sure how to help without insulting your swuftness and just wasting and confusing your prob!! Alot can be solved with plug selection for sure.. By the way these plugs solved my prob with fouling the Hi $$ NGK's when ever i left the enrichner on for more than needed! Actually i never need to use it now. or when i had my 1200, I know have a diff bike, a bandit on steroids i call it!  

[ptitza]

2Daytona:
Ok, it's doable, i have plug wrench with me, so i'll try doing it later today.
Hate taking out plugs without fairing removal, but i'll live.
As for the mileage, i've made an error converting from metric, it's 70k miles now(112K km.).
Additional strange thing is that i recall that during carbs sync and adjustment I was unable to set RPM around 1.5K - it was either <>1K, or jumped right to 2K.
As for the past problems, they never solved.
I blame dynojet kit, but I was unable to obtain stock jets and needles - only way to do it here is to order from dealer, and this is very expensive (multiply US prices by two). Obtaining a different plug type is also difficult, even standard NGK ones have to be ordered(and they cost around $15 each here).

[Daytona]

Just try the champions!