Compression values

[Snow]

As probably a few of you are aware, I stole away Dave Hogue's ride this past weekend. Though I didn't have the time to spare, I went ahead and replaced the cams in this bike last night (was a pita with the new chain - took me about 1.5 hours). This morning I took compression readings and had the following results:

1:150
2:125
3:150
4:150

Note: this bike has been sitting since 2000 AFAIK with no exhaust or intake boots in the garage. Could 2's valves be a little rusty? When I take the percentage of what 125 is below 150, I get 10.7% - will this be alright? Perhaps I should suck some seafoam into the cylinders when I get her ready to run?

[TADracer]

As far as I know, compression should be within 10% from hole to hole so you are probably OK. Besides, it may come up with alittle bit of riding. The 150 numbers look good though.

[John]

The 10.75% isn't too bad, but have you determined if it is rings or valves? Did you have the throttle twisted open when you did the comp test? It needs to be when doing a comp test. Just riding it a few hundred miles may help free up a sticky ring, or knock any carbon off the valve/seat. Some Seafoam, Marvel Mystery Oil, or some diesel fuel left sitting in the cylinder may be helpful also. Try any of those, and let us know what you're results are.

[TADracer]

Sorry, should have put this in my previous post.

Did you try a leakdown test?

[Erik the Red]

Not trying to be a smart@$$ here, but I think you miscalculated the percentage. (150-125)/150 = .1666 -->16.7%

10% below on 150 would be 135.

[Snow]

Bah, I hate math. The bike doesn't have carbs on it right now so I'm assuming I wouldn't have to open the throttle

[DiverRay]

Snow,
Just put in MM oil, or ATF into each intake. Turn the engine over SLOWLY by hand, and let set for a day or two. Then do the compression check one more time. You should see the 125 come up a little. As John said, you really need to ride it for a few hundred miles to loosen everything up.

[81xsproject]

I am sure he knows this and so does Ray, but pull the plugs before you do this or you could create problems.

[Snow]

Hydrolock!

I think I mispoke the 1,3,4 values earlier - they were closer to 140 than 150, which should bring it into 10% range. I'm going to see if I can't get the carbs and exhaust on and get this puppy running tonight - should I do an oil change considering how long she sat?

[Erik the Red]

Yeah, 140 instead of 150 would give you the 10.7% you had originally stated. Simple typo. -at least that's easier to fix than out-of-spec compression.

Since it's been sitting since 2000, I'd definitely change the oil before taking it out for a ride. Always good to have fresh blood in the heart of your machine. 6-7 years is plenty of time for the oil to break down. Changing it is easy insurance against bad things.

[Snow]

Btw, when I was installing the #3 intake cam bearing, I messed up and the washer and nut fell (or flew, depending on how you look at it)...I thought into the cam chain chasm...fortunately, after a tense 15 minutes shining a flashlight down the cam chain hole, I saw that they fell onto the head *next* to the spark plug hole...yes...there is a reason I pray...