Intake manifold leak fixed

Dodged a bullet. . .

While cleaning off some oily resdue from the head last night, I discovered that the water stream would make my bike start misfiring, running on three cylinders or stalling entirely. I thought it was electrical at first, so I was careful to redirect the water stream. The bike still stalled when I shot water around the carbs, so I started checking the manifolds. Sure enough, there was enough of a vacuum leak to cause the bike to stall if I sent enough water around the area. I let everything dry off and tried again with carburetor cleaner, with the same results. Two of the four were so leaky that only a little bit of carb cleaner would stall the engine, and the other two were leaky enough to cause the bike to only run on the other three cylinders while I was spraying the cleaner.

So because I like to ride more than repair najor damage that can occur due to vacuum leaks, this morning I broke out the gasket paper and used it and some RTV on the gaskets I cut to seal the leaks. What a difference this makes.

The bike had been running pretty much ok, although I had previously opened up the pilot screws to compensate for this problem. I didn't know why the idle was erratic at the time. After pulling the manifolds, filing them as flat as possible, and using the gasket paper / RTV, the engine runs much smoother, and I was able to turn the screws in to probably a whole lot closer to factory specs.

Something that made the reinstallation of the intake boots a lot easier, was my boilong them in hot water for about 10 minutes. They got really pliable, and that made this job less of a nightmare.

:lol:

I ran into the same thing on my KZ305. I was doing a little tuning trying to get this thing roadworthy after it had not been driven in years. Had it running and sprayed ether around the intake boots while running, and sure enough the idle increased. Took my intake boots off, cleaned them really well and filled the cracks with RTV, and it did idle a lot smoother (like anything would by fixing a vaccum leak). I hate to fix things this way, but I just don't feel like forking over the extra $$ for intake boots on this bike right now as they are pretty expensive and i only need 2 of them.

Boiling/soaking sounds like an even better method than saturating with formula 409 -- which my buddy Mike switched to after swearing off Armor All.

Klaus,
Does Formula 409 soften the rubber?

Personally, I think it prudent to get new carb holders when I pick up a used vintage bike. The rubber hardens after a few years and won't seal. It might be possible to fix cracks with silicon or other goop or soften the holders temporarily by various means but I feel that it is safest to just replace these bits. Anyone who has holed a piston after "fixing" a carb holder will understand why. ALL rubber bits on an older motorcycle are trash after a few years.