1978 750F low compression

[Jonny]

I am the original owner of a 78 CB 750F with 28,800 miles. I rode it in a spirited way but never raced it or beat on it. I did meticulous maintenance and upkeep. In 1988 I put it into storage. This summer, I decided to revive it and did all the required things such as oil & filter, carb rebuild, fuel tank flush, new battery, squirted oil into the cylinders and onto cam, set valve clearances etc., etc. I have run it (total of 13 miles) at 30 mph or less in the neighborhood since the restart. It has some blue smoke in the exhaust which it never had previously. So I did a compression check. I trust the gauge, did the test with wide open throttle, and a strong battery. I have 125/120/115/125.
Is there a chance the rings are partially stuck and will free up with more miles/load/heat cycles? Or should I just go ahead and consider it in need of a teardown as a winter project? Thanks.

 

[dirtdigger]

It probably did get some surface rust on the cylinders and the valve seats after sitting that many years. If you got the tune up good I would take it out for a good run on the highway(or some spirited runs down the road) so you really work the engine. You wont really be out much if it doesnt work. Good chance it will pick up some compression if its just a bit of surface rust.

 

[BAHNST]

Fwiw.... remember for small cylinder cc motors compression testers arent always accurate....in terms of absolute value...especially those with a long rubber hose from engine to gauge.
Its the difference between cylinders u are looking for IF engine starts easily and runs well.....

 

[Jonny]

Thank you friends. It confirms what I really wanted to do; that is, ride it and reassess after a few hundred miles.