I'm trying to figure out what is in my carbs and how to get it somewhat leaner. My mileage could be better and there is still some soot accumulating on the exhaust. When I bought the bike a year ago it was already 20 years old and changed hands an unknown amount of times. The people I bought it from had it 9 years but barely used it. I've put twice the miles on it in the 9 months I've had it.
The bike had an unknown make 4-1 header with a Yamaha muffler when I bought it. I put it back to a stock pipe. Airbox is stock foam with some large holes right above the snorkel.
Altitude is just shy of 6 feet above sea level when I'm standing up (near the beach). The highest mountains near me are about 5,000 feet. I've had the bike up to ~9,000 feet near Yosemite and it was very unhappy about that.
I have an extra set of rusty carbs I got cheaply for extra parts. The main jets in them are marked 102.5, the needle jets are brass in color with no adjustment steps.
The carbs that came in the bike have main jets marked 96 and the needle jets are steel/aluminum color with adjustment steps for the C clip, currently on second from end.
Neither of the main jet markings matches the Mikuni numbers in the chart on the previous page of this thread. Maybe it currently has a DynoJet kit?
Width(thousands)------Kehein # -- DynoJets # -- Mikuni #
...
0,0370---- 97,5--------- 96----------- 90,0
...
0,0390---- 102,5------- 100---------- 93,8
The carb kit I bought had the wrong float needles and the bike flooded. The needles from the rusted carbs look better condition than the ones that were in there so I used those when I put it back together again. Now it's no longer leaking out but is still flooding a bit from the smell, the acceleration sucks and it won't hold a steady idle. I used stock float level and maybe that isn't right with the jetting kit. Also some of the linkage may be sticking up a bit.
I replaced the two o-rings on the float plastics and the tiny o-ring by the diaphragm with Viton ones.
I didn't do any adjustments to the mixture levels since it idled well before cleaning and no jets were changed. The plugs were gone so someone somewhere did when they did the jet kit.
Any other comments or suggestions on this? Thanks all and happy mothers day (in the US).
EDIT: Tearing it all apart again this evening found the mixture screws were out 4 turns, seems a bit much. Replaced those o-rings and put them to 2 1/2 turns. Will re-set the float levels and put it all back together tomorrow.
EDIT AGAIN: Got it back together with the correct float needles. No more gas leakage but it idles like crap. Runs up to 5~6k RPM then very slowly drops down and dies. High speed seems decent but quite a few flat spots in acceleration. Will put the mixture screws back to 4 turns where they were and make sure the slides are moving freely. Float levels are set to 15mm on the highest float, they don't sit evenly. The o-rings are seated ok. Any other suggestions on why it would do this?
FINAL EDIT: Just to not leave it hanging... The symptoms I had pointed to a vacuum leak. I put the idle mixtures back to 4 turns. Then meticulously cleaned and assembled the diaphragms, needles, covers, etc, and put it all back together. Made extra sure to fully seat the carbs into the intake manifold and the airbox onto the carbs. Added clamps to most of the hoses. Started up rough but slowly got better over a ~5 mile ride at high RPM/Speed. Now seems ok except for a bit less 'off the line' acceleration than it had before. I'm assuming that may be helped by syncing the carbs.
