after changing exhaust, seems to have one cylinder miss under 3 Grand RPM's

[xj11john]

I had gone up 3 sizes on pilot jets from 117.5 to 122.5 (or 121.5 )since I had 4-1 exhaust and individual filter (cone style) and was running great after cleaning carbs, jetting, and syncing and getting floats to about 23 mm.
Then I changed to 4-2 after market pipes with no crossover, seems to me jetting would still be ok since I still have indy filters and modded exhaust,
What would be the first thing you guys would check? I was thinking float levels... but maybe something simple first?
It feels like the #1 or #2 cyl is not hitting till 3-3.5 grand RPM's, and seems to just started recently, any suggestions welcome, and thanks in advance.

[xj11john]

The jetting was 112.5, and changed to 122.5, had to look back at earlier post, thanks again. I think I am going to let it idle and check to see if the pipes are all hot by spraying them with a spray bottle and then check plug color first, also I cant remember but would changing the idle mixture screw help me at all in midrange or just at idle, so can I rule that out. I will prob mess with those at idle just to see if I can make her idle better again, but as I said will that help me at any other RPM? thanks for listening to me try to work this out in my head and in print

[TopCatGr58]

Hey John,

Yes, spritzing the pipes during idle is a good first test. The Jets you changed were the MAIN jets! Adjusting the pilot jet idle screws more turns out will increase the fuel in the mix, and it does provide input for your low rpm and early midrange performance before the mains kick in fully!

However, if your pipes are cold on #1 and 2, then it could be a fuel delivery problem to those carbs!! Can't remember what work you've done to the bike, carbs, so can't really talk about whether another cleaning is in order?

Did you make the special XJ YICS tool and vacuum synch the carbs? Are you still running the octopus? Any work done to the petcocks? Lots of things to check!
T.C.

[excess11]

Electrical

If the miss is in #1 & #3 then it could be an electrical issue. (the dreaded pick-up coils,ignition coils,bad plug wires) Maybe its just an odd series of events that it started after exhaust change and is not related to this mod at all !!!! Hey it could be as easy as fouled plugs from the new jetting, What do you think.

[TopCatGr58]

Hey Dan,

I think you mean 1 and 4 which are linked by the same coil and PU coil, not 1 and 3!
T.C.

[excess11]

TC is a motorcycle genius/no joke!!!!!

Yeah!!! What he said.

[xj11john]

Thanks for those comments guys, havent checked anything yet but will do that spray test soon, and try adjusting the pilot screws.

Yes T.C. I guess those were main jets, also I have gotten rid of the octopus. When I had it synced the mech did it without plugging the YICS system and just made the mercury match the way it was, but it was running good after that so I don't know if that would come to play now or not.

Thanks again for the input guys.

[DiverRay]

If the mech didn't plug the YICS, he didn't sync the carbs!!!! You CANNOT sync the YICS without blocking the ports.
The running problem can be the vent tube on the carbs, or junk flowing into the carb on one pair, or the pickup coils. After you check the headers, you should have a good idea of where to look. If it's 1&4 or 2&3, it's electrical. Anything else should be fuel .
Ray

[50gary]

DiverRay, tell me about the vent tubes? I have open type filters and no air box, new petcocks gravity feed (no vacuum) Stock jetting and a "rough passage" getting past 3000 RPM. By that I mean a flat spot and a rough sound. Stock exhaust. Double cleaned the carbs and floats are right at 1.012" I have 5/16" fuel line tubing running up from the vents about 5" but open to the atmosphere under the tank.
Cheers, 50gary

[DiverRay]

50gary,
I would put a fuel filter on the end of the vent tubes. Use the paper type, so you don't get a "vapor lock" from water. If the tube you have on have a bend, and just a little water, they can cause a "blocked vent" type condition, and be a problem that can be hard to find.
Ray

[50gary]

Thanks for that tip, will do.
Cheers, 50gary

[xj11john]

Thanks Ray,

I may have the mech, sync them again if he has the tool or can make one to block off the Yics sys. thanks all for your comments, still havenet had time to mess with it, and first needs and oil change bad, I'll let you all know what I find.

John