XJ600N funny ignition problem

Hello

I have a 1997 XJ 600 N model. I dont have it for long, didnt notice this when viewing bike. It have a strange issue. It starts imediately, runs on idle, pulls like a train, it goes like it should. The issue is, when its cold engine, 2 cylinders (2 and 3) dont work - exhsust headers cold. But only on low revs, above 3500 it is normal. If i go for a drive, all cylinders works, ehxausts headers have same temperature.

Tested so far:
-spark plugs interchanged, no change
-coil resistance measured, its on spec
-spark present at all times on all cylinders, tested with an old spark plug, cant say about quality of spark
-when i pull spark plugs out, they are dry and of the perfect colour, all 4

Am i wrong to assume that its a spark issue, because 2 and 3 are on same coil? Dont know state of carb cleaning. Could be a carb issue?

 

absolutely, probably plugged up starter jet in bottom of 2 and 3 float bowls

 

How about the ignition trigger pickup?

 

I guess no way to get to starter jet with carbs on bike, right?
How can i test pickup?

 

just realised you have a 1997 model, i think your carbs are fitted with heaters, not sure how they work, nor am i familiar with them , it may be worth checking your model to see if they could be the problem , do you have the workshop manual for the bike ?

 

his bike only has one pick-up, - other 2 cylinders work fine, but could be the pick-up isnt firing the other coil somehow

 

I have workshop manual, just got it. Will check the heaters today, they are easy akcessible. But you think they could made such impact?

It seems wierd why would the pickup not working hapen only on the low rpm, and cold, then sudelny starts working. Will look in workshop manual if there is way to test.

 

Only thing i cam find wrong, is wrong spark plug caps and maybe wrong spark plugs. If i am not wrong, there should be 10k OM caps and no resistance plugs. But here is 5k caps and 5k plugs, so should be okay somehow?

 

If the manual says 10K, any combination to equal 10K is ok.

 

I think i found out. Its intake boot rubbers, cracked.