Cylinders 1 and 3 will not fire after reassemble - ...stumped...

Well, I don't have a feeler gauge small enough yet, but there is definitely more room on the exhaust valves on the first cylinder than on the fourth cylinder. With my thumb, the fourth cylinder is almost difficult to cover (or maybe I'm just timid), but the cylinders 1 and 3 I can seal with my thumb. There's definitely a compression problem of some kind.

Is there any problem with using "used" valve shims? I have my old head and the new one came with it's own valve shims and lifter buckets. I figure with the ones I have I should be able to swap them all around to meet the necessary clearances if I can reuse the old ones. I need to get a better feeler gauge and measure the shims first, though.

Another question - the rubber plugs on the ends of the head have to be glued into the head. What is a good adhesive to use for this? I don't think the one I used is going to work (glad I noticed now and not on the road). Don't remember exactly what it was I used....

There's no problem in using your old shims as long as they're not beat up.

I use 3-Bond gasket sealer for the cam end plugs, sets up nicely and my cam plugs don't leak or squeeze out.

Wiredgeorge - thanks for the insight. The valve clearances were definitely off. Cylinders 1 and 3 had no clearance at all and I had to reduce them about 0.4mm, enough to keep the valves open (I believe). This also explains the reason why I was getting air pushing out the carburetors under compression. The bike runs now - although not nearly as well as it did 6 years ago prior to stripping the spark plug chamber.

Probably going to do another rebuild this winter and replace a large number of parts that I should have replaced this time but didn't just to be cheap.

The carb slides are definitely not synchronized - what symptoms will this cause? (You appear to be quite the expert on the carburetors - expect to see mine shipped your way this winter.)