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IanFrancisco
Guest
All summer the bike ran pretty darn well but not perfect. Rock solid idle and perfect running wide open, but - At mid-throttle openings, steady rpm's, the motor would "hunt" or hestitate and give me a rocking horse ride. I thought it was the carbs which I cleaned twice but with a kind of a 'lick a promise cleaning'. I figured I would tear them completely down this winter and chase this little bug when it's cold out and not as much fun to ride. Anyway, the problem got a lot worse this week so I figured it was time to pull the carbs off and check em out. While I was at it I pulled the plugs and notice the left plug was black and sooty (rich running) while the right plug was a nice brown/tan color. This is a twin, not a 4-cyl. So, I put some new plugs in. Backing up a little, I had previously tried to raise the fuel level in the bowls by adjusting the float level because on these BS34SS carbs the needles were already raised as far as they would go, they don't have the old-school 'clip and multiple groove" setup. So, I thought that might be my problem. But, I had set both carbs up the same and only the left side was running rich, so WTF? I set the left carb back to the previous float level (maybe a difference of 3mm tops). When I put the carbs back on I did my usual trick of sucking on the vacuum line to open the petcock and fill the bowls so the bike would start and lo and behold, got a mouthful of gas for my trouble. It never did that before. Ok, from the wealth of knowledge I have found here I know that I have a leaky petcock and the left cylinder is sucking in gas from the vacuum line. To confirm I plug the vacuum line on the carb and the bike runs like new for about a hundred yards till the carbs empty. My petcock says "On" and "Res", not PRIme like others. Isn't it supposed to allow fuel to flow on Reserve with or without vacuum? I pull the tank off (just filled it up, daggamit) and emptied most of it into my gas can and dumped the rest. Pulling the petcock apart I find a big thin metal washer-like thing on the vacuum side in pieces, and the diaphram in decent shape except for where it seals around the piston/plunger/valve thing. There's my leak. From another site (www.umgweb.com) I remember a story about how someone used superglue to "bodge" (jerry-rig) a cv carb diaphram since they were on a budget. So, out comes the superglue and I run a bead around the piston/plunger/valve thing on both sides, throw away the pieces of washer, let it dry and throw it back together. My bike is now running like a top, smooth stutter-free power available at any throttle position or rpm. Too bad I didn't get to this earlier this summer, but the bike was running pretty well, and it was riding time!! Anyway, none of this is earth-shattering news, but I thought I'd share that this particular petcock needs vacuum to flow fuel in either position. There is a screw that you can loosen that will allow gas to flow to empty it, but then it leaks from the screw while flowing fuel through the hose. Not useful for riding with a leaky petcock diaphram. SO, this little diaphram is a mission-critical item on my bike, a single point of failure that will cause running problems. Seems dumb to make what I consider a luxury item, an extra "bell or whistle", something that has to work right for the bike to run right. I guess I will be shopping for a petcock rebuild kit or a non-vacuum type petcock in the near future. Any sources? I have heard a name which I can't remember at the moment... Pingel ? I don't want to spend a ton of money for a petcock. How about a cheap non-vacuum type? Any suggestions?
