Rude, 1957 Bigtwin advise, opinion on compression range..help

[kodibass]

Hi
I have a 57 rude bigtwin sn# 25029-11326 this engine sat under a house for 3o years, it was seized up when I got it, I sprayed penetrating oil in each cylinder and let it soak for 10 days, and put a big breaker bar on her and she now turns over, I did a compression test with the electric starter and here are the numbers top cylinder is 110 & bottom is 147, what would cause this kind of range difference? I was thinking it could be just a ring sticking in the top cylinder and maybe if I could get her to start they might even out a bit, But will this thing even run with that kind of range difference? are there other things that would cause this? To me the bottom cylinder at almost 150 seems almost to high, or could this be from the penetrating oil? Anyway I would appreciate any help / advise, opinions, I really want to save this thing it dripps with KOOOOOL, thanks i/a

 

[1946Zephyr]

Re: Rude, 1957 Bigtwin advise, opinion on compression range..help

This is normal, simply because the rings are sticky and the cylinder walls are not quite the same, as far as the rings being seated in. The best thing I would suggest is get the old gem running and do a de-carb with some sea-foam. Run it for an hour and retake your compression test. If you get all the rings loosened up from from the de-carb and running, the numbers should improve. Typically, you want the compression numbers to be as even as possible, but a motor that sat for 30 years, it pretty unlikely, especially after being stuck.

The '57 Big Twin is one of my favorite motors, by the way. Truthfully, it's about the best built motor in the era and even better than the modern ones. It will be worth every dime you put into it, even if you have to pull it all down and restore it.