number 4 running cold

[rizzo4u2]

i ran the bike and all is good except for no 4 cylinder, i did the spray test on all and number 4 is running cold, i pulled the plug and replaced it with another, checked for spark , good there, checked the carb for fuel and all is good, what would cause one cylinder not to run hot, the wires are decent and in good shape, im running accell coils and wires. this all started when my carbs had to go due to all the air mixture holes were in bad shape ,i bought another set of carbs went over them for the clean up and check, they run better than my old ones except for this problem that came up, noticed it didnt have the smoothness and response that it should and that no 4 did not pass the spray test

[tadtl1]

pilot fuel jet in bowl

Why dont you check the,,,,,, pilot fuel jet,,,,, in the bowl of the carb, that sure killed my number two until it was cleaned out. this is the jet that is placed in the back of the bowl, NOT the usual jet thats called a pilot jet that sits next to the main jet,,,,,its the one that the copper tube goes into, I am told the jet inside that thing is only one mm ,, so it is super tiny,, mine only came clean after multiple soakings and compressed air blowthru s. Or for a quickie test, switch the bowls from three to four and vice versa and see if the number three pipe is cooler then.

[tadtl1]

what happened to idle mix holes

Hi,

I am curious as to what happened to your idle mix screw holes in the other original set of carbs.

[rizzo4u2]

broken air mixture screws in the past that were hard to get out and ruined the hole size

[tadtl1]

yes to that

Hi,

I had the same thing happen, but hopefully there are no damaged threads that I can see, at least the new jets that go in, set there properly so far, I sure hope they dont end up leaking or loosening

[rizzo4u2]

after some time i should of put a bandage on these babys .i have been picking up the cores for these for the just in case in the future ,i swaped out the 3 to4 will see how this goes, ill get back to you , thankyou

[rizzo4u2]

well i tried the bowl change and nothing the same old same old on number4, i feel it is a electrical problem now now 1and 4 has dropped off possibly the ignition box or the pick ups , i also tried when i just lost no 4 was to take no. 4 and put it on no. 1 no change to that cylinder no1 stayed hot and no 4 didnt after running for about 10 min.........have any more ideas

[DGXSER]

IF you changed the spark plugs, and the wires betwen 1 and 4 and the problem stayed with no 4, then it is in the carbs IMO.

Go back through that carb meticulously. Did you perhaps pull the needle jet out of the slide by removing those two screws from the plate inside the slide and pulling the washer and srping and needle out? I did this when I first rebuilt my carbs on no 1 and I happened to put the needle, washer, and spring back in the wrong order. This caused no 1 to foul out at idle or low RPM. Took me several months to figure that one out. Once I corrected the issue with the needle jet, the bike ran perfect ever since.