same old carb problem

[sissonk]

81 GS850X from usa.
First the problem --is miss-fireing from 2-4k rpm when riding it above 4k its like a rocket , its like a peaking 2stroke engine. At idle the pilot screws don't make any difference above 3.5 turns which is were I have them to get the bike to start and run some carbs are at 4 turns . the sync of all 4 is good and the vac levels are high enough . I had 4 42.5 pilot jets so I replace the std. 40 jets and it runs a bit better . I can't find what the problem is as the engine ran perfect 6 months ago when the settings were 2.5 to 3 turns . I have checked everything , the valve clearances , compression is hi , no air leaks , the ignition is Dyna S which is very accurate and I have even checked that the spark is there for every pulse . but I remember a car I had had this exact problem and it was the coil .Though the color tune plug I can see the spark but there is no adjustment with the pilot screws.
any thoughts anyone ?

[Dave8338]

Which carbs are on the bike?

[Steve]

'81 model should have the VMs, right?


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[sissonk]

the carbs are the Bs ones CV type. I have cleaned them throughally(bad spelling) I noticed today that exhaust pipe on 2 and 3 cylinders are both cool at idle , the mixture is so lean that they don't produce power , used color tune plug and turned pilot screw out to 5 turns it made no difference. exchanged the coils but that made no difference either. I can see the spark in the plug. I don't know were to go from here .

[SqDancerLynn1]

Being that it is cyl 2&3 most likley rules out the coils, You Still have a carb problem
need to clean them again