carb jet and clutch disaster

[kenco]

Hi, i want to up a size on the main jet, I take it the next size up from standard (122.5) will be 125. I have read the carb guide, but i haven't seen a copy of a size chart for main jets. Also i want to drop the needle by 1 notch, If the clip is on notch 3. Does it mean drop the circlip to 2 or 4 ??
Also replaced the pesky starter spring, had a couple of goes at rebuilding the clutch housing, on the second attempt i found that the center hub was running out alighn. I removed the basket and that the needle roller bearing had broken up and the thrust washer that goes on before the bearing broken. Am i right in thinking its an error on my part not making sure they were seated properly before torquing up the nut. Or is there an underlying fault elsewhere.

 

[5twins]

Mikuni mains are sized in 2.5 number increments so, yes, 125 would be the next size up. They would then progress on up to 127.5, 130, 132.5, etc. Mikuni needle slots are numbered from the top down .....

To drop or lower (lean) the needle, raise the clip. In your case with the clip in the #3 slot, move it up to the #2 slot.

Yes, I think you had the washer and bearing out of place when you tightened things down.

 

[kenco]

Thanks 5twins, the carb guide is great by the way, you gave me a fair bit of stick last time i posted a question about carbs. Forgot to mention in the first post the bike is fitted with ramair filters and modified muffler.

Ken

 

[5twins]

I have similar mods on my '78 (pods and Mike's Commando mufflers). In the '76-'77 carbs I set up for it, my final jetting is 132.5 mains, 27.5 pilots, and needles leaned one step to slot #2. 132.5 were the largest mains they would take, probably due to the large Z-8 needle jets in these carbs. In the original '78 carbs with leaner Z-2 needle jets, I'm able to run 140 mains on the same bike.