Cub

I hate when someone posts a question and get answers but you never hear the outcome. So. I posted about a cub I have that had sat for a couple months and not started. It just wouldn't start. I cleane the carb cleaned and adjusted the points, rechecked the points , the timing , and everything I could think of to check. I was to the point of tearing it down because yhe compression was low. Anyway, I took the head off and found no wear in the cylinder walls, no ring ridge and no scaring, but there was so much carbon on the valves that there was no way for them to seat properly' I put a small wire wheel in a drill and turned the engine till each valve was up and gently cleaned each valve . After all were cleaned I put the head back on and she fired right up. after she warmed up I had a small water leak at the thermostat housing so I cleaned the mating surfaces good and made a new gasket for it and that problem fixed. I want to thank everyone for their helpful suggestions Who would have thought that carbon would build up that bad on the valves. I guess that is a by-product of not running it enough at a time to get it good and warm, or at least that is all I can figure Thanks for the help, Nat

Cubs have valve stems that hang down, this usually prevents excess oil from being pulled into the engine and "coking" (proper term) the valve head. Low power use can allow buildup due to higher than normal vacuum (running at small throttle settings). Modern multi weight oil (like 10-40 automotive or 15-40 diesel grade) can make a great difference. Thanks for posting back Jim

On my little 1977 cub I switched to Shell Rotella. Also changed over the 300U. So far the stuff runs very clean.

Had a problem with valves in Cyl. 3 & 4 hanging up in the guides. Started using a couple ounces of Marvel Mystery Oil in the fuel at each filling - problem solved.

Congratulations on getting it going NAT. One note, that is not a thermostat housing, only a water outlet. If someone has put a thermostat in it, it will restrict the coolant flow and cause it to overheat if worked very hard in warm weather.