Loss of power

TexasDav · #1 05-08-2009, 04:21 PM

I thought I have run into every problem that could happen with the 80 (69cc) china motor.
I have fixed my motor with the help of the great people on this forum, but I am stumped this time.
My motor has been running great after many bugs were worked out. It has been dependable transportation to and from work. I just hit 1,100 miles and then after a good ride to work, it started hard, and had no power going home. I did one thing at a time (learning the hard way, not doing too many things and get lost) to fix the problem. This is the list of things I tried. After each one I did a test ride with no improvement.
I put a new plug, I checked for air leaks, I checked motor mounts, I cleaned carburetor, I tried another carb, I tried fresh gas, I checked the exhaust for blockage, I pulled the head and checked for carbon and scratched cylinder walls, replaced the rings. I bought another motor and it runs great, (so there is no drag from the bike causing power loss.) I hate to trash that motor, but more important is, I would like to figure the problem out so if I run into it again I can fix it. I was thinking of ordering a head and piston for my next step. I can't see where the power could have went, It is such a simple motor, and it looks in good condition.

**Dave31** · #2 05-08-2009, 04:45 PM

Hmmm... you may want to check to see if you are starting to shear the key way, you may be "out of time" a little.

Maybe a weak mag?

TexasDav · #3 05-08-2009, 04:54 PM

I forgot on the list of things checked was I tried a new Magneto, and a new CDI Igniter . I did not check key way though

**Dave31** · #4 05-08-2009, 04:56 PM

Is it possible your clutch is slipping? Maybe it needs adjustment?

TexasDav · #5 05-08-2009, 06:13 PM

not clutch, but I will have to check out that key way, that sounds like a possability

**2door** · #6 05-08-2009, 07:11 PM

Dave,
While you had the mag cover off did you notice any oily residue in the cover, under the mag? There is a possibility that the crankshaft seal went away on you and you're seeing a very lean condition. Air leak checks won't show this unless you spray whatever you're using directly on the magneto cover or around the wire exit opening. If you get an rpm increase while spraying carb cleaner on the cover you've found the problem. Seal the cover and the wires with silicone and give it a try. If the right side, clutch side seal is gone you're scr**ed, cause there's no good way to seal it from the atmosphere. PM me, I've got some more info for you.
Tom