Carbs specs are what came out of the box to start....
VM30-83
main 250
pilot 40
Needle jet P-5(159)
jet needle 6F5
cutaway 2.5
main air jet 2.0
When I put these on out of the box, the pilot was right on, idled really well. Barely off throttle and it appears to start slightly flooding, idle way down then come back up. Hardly rideable as soo as you open the bore, she'd cut out, close it and it take right off again. All I had was leaner jets as I was expecting to go down in size so I got to thinking, in case it's getting too much gas, I'd throw the next stage leaner main and see what happens. Threw a 240 in, set the needle in the middle, and the bike actually ran better off throttle. Stomp it good and she'd cut out but if you got it revved up around 4k, she'd roll under it's own power decent enough, smoothed out a little, drivable. I did notice the pilots seemed a shade leaner at idle so I screwed the air screw in a 1/3 of a turn and it idled good again. Screw was two turns out to begin with. Still burbled a little off throttle but nothing like it was doing.
I raised the needle up as high as it would go for the next test. Again blurbling got worse just a shade off idle, still was drivable but a shade worse, idle suffered a little. this kinda told me maybe the carb is dumping too much gas and the little motor can't take it.
I took it out and ran it like that for a few miles, just around the block and it seemed to run decent. Good power, comes on hard up around 6, noticable curve in the band. I brought it around the last leg back and when I pushed it hard, I'd hear this sliiiiiiiiight, and I mean slight, ticking from the left jug. I didn't check the right, sounded like something was tapping, maybe the piston hitting the head gasket or head, so I brought it back. Figured now be a good time for a teardown and see what's going on inside this motor.
Opened it up to check it out and everything looked great. Pistons werent marked, no head tap, good flame front to the edges of the piston and head. Had a center head gasket get something under it or something as it spit oil on the underside of the head. Pulled the jugs, all in order, checked the pistons, all good there, rings great shape, no flash on the sides of the piston.
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Put the bike together again, took a look at the cylinder mounting and piston, seems I may see the culprit. The pistons are starting to lean from break in and the back is up higher than the front, looks to be .005 exposed above the deck. Looked at the head gasket, didn't see where it was chafed on the inside, looked all good there, centered it up, and with the tight fit on the hole, it may have been tapping it. I replaced the head gaskets and added one of the paper thin base gaskets to the bottom to shim it up a little it was all below the deck. I don't like using double gaskets under pressure because they can blow, but the thicker gasket material seems to be 'pressed' for a fit to the other gasket now that it's been on the engine a while. I'm gonna run it and see what happens. I havent ruled out anything yet but for safety, we'll shim it clear to be sure nothing is hitting.
It's all together in the shop. I put 230s in this time as it seemed to like the leaner jet. Needle is in the middle, pilot left be. Right now it's benched because I gotta fix a leak on the petcock before I can do anymore with it and I'm waiting on the glue to harden. Don't ask,
drastic times call for drastic measures.
Tomorrow is another day......and Jim, I'll be looking into slotting those out after I get the bugs worked out.
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