After it warms up it wants to idel ruff and die. Then hard to start. It starts harder now then what it used to even when cold. I checked compression and it was reading 70psi. I then added a little oil to cylinder and rechecked. Read 90psi with oil then it went up to 120psi after a couple more test.
I finally found in manual it says 50-90psi average is normal. That sounds very low to me???

I have not check valve gap yet. But do you think my compression is low?

 

Check that valves have .006 clearance on intake and exhaust. With the decompression function on the cam compression is not always accurate. If valves are with in clearance,then I would check out carb also,could be just needle and seat worn causing engine to "load up" with gas and idle rough and die. If carb is ruled out along with valve clearance,then could possibly be time for a new piston and rings. Just eliminate the carb and valve clearance first.Also check around intake boot,could be cracked causing air leakage and rough running. OPT

 

....tech
Thanks, The valves were out. Intake was .018 and exhaust was .012. Since I do not have right tools to do a leak down check I did what I would call second best. I blew air in spark plug and check for air leaks in valves and in case(oil dipstick). There was no air leak past the valves but did have air coming through the rings. So I do think the rings are starting to go and the valves are good.

After the test and reseting the valves,gap, it does seem to be running better. I did not have time to do a good running test to see if the valve adjustment will fix it.

 

I have a cylinder leakage dual gauge that just screws into the plug hole and I usually cranked it up to about 90 psi at TDC. You can listen through exhaust for any exhaust valve leakage,plus at back of carb(for intake valve leakage) and crank case vent.DON'T think I ever found an engine that would hold 100 percent! Usually had about 5-10 percent leakage on the other gauge is what I would find on engines in "good" condition! This is considered "acceptable" on most engines. More than 20 percent indicates count down for future head work or new piston and rings! I would just run the machine and see how it does first! If starts smoking or still runs bad,then probably time to tear down. If you do be sure to have cylinder measured for wear(bore to next oversize if needed) as just replacing with "standard piston and rings"may not do the job.Plus I would clean the head and lap valves and new valve guide seals. Only two valves and you have take the head off any way. I always just considered this a "patch job" if you don't! Just run it and keep us up dated. OPT

 

I was able to test run it today. Runs like new--- almost new anyway.

.....Tech
I tested the valves as you stated. The air leak through the rings was quite noticable. I do not under stand when you say leakage 5-10 percent. I just do not understand the 'percent thing'. Percent of what? How do you measure it?

 

By percentage means approximately 5-10 percent leakage is acceptable of the amount of air introduced into the head and cylinder. That is 10 percent max loss from say 90 psi which is what I pressure up to on the main gauge, approximately 80-85 psi is acceptable on the other. This is considered "normal" percent allowed leakage! If you have 90 psi on the main gauge and over 20 percent leakage on the second gauge (which is actually divided into a green area(acceptable) yellow area(moderate leakage) and red (severe leakage) then you may need to check the engine out. Just look up Matco cylinder leakage tester (which I have) OR Snap-on. If you can see a picture of the gauge set will help you understand better (picture's worth a thousand words!) OPT