Anyone???

 

I don't know if I am way of base here........but I don't think that it will read properly unless you remove the decompression pin from the camshaft.........

 

I think you nailed it on the head yourself! [img]i/expressions/face-icon-small-wink.gif[/img] I think he was on the wrong TDC when he adjusted the valves. Same thing happened to me. I went off the wrong Top dead center(four stroke remember?, so there are TWO TDC's.) with my valve adjustment, and it clanked and clattered like crazy, wouldn't start, etc. That sounds EXACTLY like what it is too me. Ask your father if he had to REALLY back off on the adjusters to make it come into spec. If he did thats my first guess, and I'm willing to bet thats your problem.

 

Yeah, I think its the cause.

I dont know about the decomp pin, I checked it once before with a stock piston and it was low because of valve problems. I would think that the decomp pin only works some of the time because you dont want it working while the engine is running. I know what they do, but I guess I'm not clear on how or when.

I would really appreciate any info on the proper compresssion for the engine though. Maybe If I covert the engine size from cc to sq inches and then multiply that by the compression ratio to get proper PSI readings???

 

This is straight from the manual (worded by me). Make sure valves are adjusted correct. Make sure the battery is fully charged. Start the engine for a couple minutes for warm-up. Shut the engine off and install tester. Hold the throttle wide open and crank the engine over until the guage will not read any higher. At sea level you should get 181psi with 149 being low limits and 192 being high limits. If high PSI = check for deposits atop piston or combustion chamber. If low PSI = squirt a few drops of oil in the cylinder and re-check. NOW, If the PSI reads higher = worn or damaged rings cylinder piston. If the PSI stays the same = blown head gasket or defective valves. Remember this is for a stocker. Hope this helps.
Gary

 

Thanks gary, you and the other raptor veterans are always around when I need ya.

I've got sand drags saturday, If I can get her going. I'm going to experiment with the jetting, maybe drop to 175/180 and see how it goes. Thanks again.

 

UPDATE:

So the compression was 110 psi at 600 ft elevation. The decomp pin in the cam is installed backwards, valves are way out of adjustment, ring gap is huge, and timing was questionable. Its being rebuilt right now by a tech I know and trust. He was a dealer service manager for a few years until the dealership moved out. It was a toyota dealership that sold yammis, go figure... Anyway, thanks for your help and I may be getting a new 686 soon, whether I want it or not.

 

Thanks for the update. It seems like you had more problems than expected. I hope you get your bike back soon bro.