Could this be my air leak problem?

[Guest]

To recap, I've been having idle issues as follows since I bought the bike two months ago:

1. idle too low until engine warms up, engine stalls in neutral.

2. idle way too high when engine is fully warm.

Members suggested my problem was bad o-rings in the carb boots. I removed the carbs and one boot today and here is what I found:



The stuff that looks like casting flash on the boot is actually liquid gasket. It's on the outside of the O-ring on the boot, and on the inside on the engine side. The O-ring itself looks like new. (I was told that the engine had been rebuilt in the year before I bought the bike.)

I don't believe that this stuff is supposed to be around the carb boot/engine joint. Is it possible that this is preventing the boot and the o-ring from doing their job and causing the air leaks that are messing up my idle?

I haven't checked the other three as I wanted to post about this one without delay. For now I'll assume they are in the same condition.

Thanks.

[mike_of_bbg]

Looks like someone tried to fix a leaky/separating boot rather than replace it. Maybe the others are like that too. It'll be about $100 to get new boots but you won't have to worry about them for a long time.

[FiremanBob]

Actually, the boots themselves look new. But I also noticed that the o-rings were very poor quality with a lot of rubber mold flash on them and they also seemed a little damaged by the gas. The new O-rings I bought from Robert Barr are of obviously much better quality.

[mike_of_bbg]

Poor quality O-rings can do it. They need to be Viton or similar material that can handle the heat and gas!

[Big T]

The poor quality of the "rebuild" is indicated by your photos

If the boots are still pliable (you should be able to squeeze the open end together), break out the mineral spirits or acetone and your rubber gloves and see how much of that sealer you can remove from the boots and head

Then, reinstall the boots with the new O rings and I'll bet your problem will be solved

[FiremanBob]

Thanks. We got the boots and head nice and clean, and the new o-rings are a much better fit than the old, so I'm hopeful.

We also had to remove the cam cover and spent almost two hours scraping liquid gasket off the head and cover because the "mechanic" had used that instead of a real gasket. Without the thickness of a proper gasket, the cover was pushed down too close to the cams and that's why the tach drive gear got damaged. We knew we'd have to do this job in order to install the new tach drive correctly.

While we were at it we checked all the valve clearances which were in spec except for two that were .004. Since it doesn't sound clattery and in fact runs nice and quiet, I'm not going to bother changing the shims on those.

While torquing the cam cover bolts, we had one that wouldn't tighten. My first thought was that the threads in the head were stripped, but it turned out to be just that the bolt was too short - the "mechanic" had used only one of the longer bolts where the knock pins are, and substituted a short bolt at the other corner. Off to Ace tomorrow, then will finish the job before dinner.

I know that the real unpleasant job will be re-installing the carbs. I don't suppose they could have designed the airbox to fit inside the frame so that it could move back more than a half-inch. No, that would make it too easy for us...