uniformly low compression

Presumptuous-schmumtuous...
As long as you are dropping by, there will always be floor space. I am kinda curious myself as to the valve clearances and double check the compression. Of course, if my 90 engine arrives in time, we'll have to play with that too!

I double-checked over the weekend, and it turns out that I'm getting:

1: 105 PSI
2: 125 PSI
3: 150 PSI
4: 150 PSI

while cranking the electric start at WOT. I've got valve clearance numbers that I'll post tomorrow.

I noted that you should try the compression test with a drop of oil in each cylinder; doing one cylinder at at time to find out if compression shot up. If it did, then your rings are definitely suspect.

Without doing things in the proper order, it is almost impossible to troubleshoot a problem. The first step would have been to get pointed at either rings or valves (the oil compression test). I think I will let others try to help you sort this out... Cheers.

WG,
You give up easily! hee hee

Chet,
I could be wrong, it's hard to diagnose problems when you don't actually have the bike in front of you, but, I would say that your valve clearances will be out of spec on a few of the cylinders. Although, I'm just guessing. Having the bike in front of me would make diagnosing things a lot easier. Of course, there is no magic way to have that happen, so you are SOL.

Do svidanja,

George, you've got a good point. I suppose I always tend to put the cart before the horse. I set out to check the valve clearance (since it's recommended regular maintenance), got sidetracked by the compression, and forgot what the whole point of the exercise was! It's an easy way to spend more time on things than strictly necessary.

I'm not going to sweat the compression for now. I'll probably just run the bike, doing normal maintenance until I have the time, money, and inclination to do more.

The sad part is that as soon as I sit down to stare at the bike, my common sense goes out the window. I used to not understand how people had trouble with computers, when lots of things can be reasoned out. When I can get some time to wrench, though, it seems that I do the same thing and disengage my brain. It's easy to say, I should check the compression, and check out the valve clearances, and I wouldn't mind cleaning things up in general but if nothing is done in a reasonable order it's all just a waste of time.

Post edited by: GargantuChet, at: 2005/10/24 12:48

Make sure you are doing the compression check with the engine fully warmed up too.

savedrider wrote:

Make sure you are doing the compression check with the engine fully warmed up too.

That part was covered to the best of my abilities. It was a long weekend... mostly my fault for being stupid. I rode 30 miles in the rain in 40 degree weather with steel-toed boots, a nice riding jacket, and my full face helmet. Gloves, socks, and pants got soaked soon after leaving the house, so it was a miserable ride.

Since this is pretty much an unknown bike to me (I hadn't so much as pulled the valve cover until Saturday), I figured I'd take some advice I'd seen somewhere on this forum and check the valve clearances. I wanted to get it done quickly in case any local shops carried shims, so that I could figure out what I needed and make it to the shop before Saturday closing.

I couldn't resist trying the compression tester, since the bike was still warm and I don't have a compression tester myself, but I didn't want to waste time messing around with compression readings when I was fighting time if I was going to be able to get my hands on some shims. I figured I'd worry about compression after the trip to the bike shop.

As it turns out I needn't have worried about time, since I couldn't find shims locally anyways. Still quite wet and cold, at that point I was in no mood to mess with things I couldn't change, so I forgot about trying oil in the cylinders.

Since I've got to order the things I'm going to wait until the weather gets truly nasty. Then I'll probably pull the carbs, remove the cams and check the shim sizes, and order a carb rebuilt set, shims, and some new airbox boots all from Z1. Proper valve clearance can't be a bad thing, nor can new carb internals. And my airbox boots are cracked... I don't think they'll much survive another carb removal!

Yeah, sort your valves then recheck compression.