In article ,
"Keith Marshall" wrote:

"Nick Hull" wrote in message
I feel like a fool for posting this since I should be able to fix it in
my sleep, but I can't. 1983 Kaweasaki Prairie 3-wheel ATV wouldn't
start. After digging into it I found the 3 screws sheared that transmit
starter torque to the flywheel. Fixed that; engine turns, has
compression (50#, admittedly low, likely dirt on valve seats that would
blow out on start since I measures 100# 2 weeks ago). Starter is
turning motor in the correct direction, the intake & exhaust valve
operate in the correct sequence when I turn the crankshaft by hand, The
spark is hot & blue and will jump a .250" gap in air. Timing is not
adjustable but a timing light seems to show a flash at the correct 10
deg BTDC.

My son had a 1974 Honda 100 that we did some work on and afterward it
wouldn't start. We had a similar situation to yours except that it was a
4-stroke and I'm getting the impression yours is a 2-stroke.

We had good fire. We obviously had fuel because the plug was getting wet.
We also had great compression though. No matter what we did it just
wouldn't crank.

We finally found out that the cam that lifted the points could be either 180
degrees out or 120 or 240, I can't remember whether it had 3 positions or 2.
At any rate, we moved it to another position and it fired right up.

But with the compression so low it seems like maybe you have a valve hanging
open.

OK, I tried the 'oil trick', it boosted the compression from 50 to 70
psi with a lot less than a teaspoon. I dribbled a very small amount of
way oil with a zoom spout oiler so it would get on the walls. Very
ecouraging result in that I could get it to fire a few times,
pop-pop-pop, whils the starter was cranking. Almost Zero power but
better than anything I had seen before. Then I stuck a soda straw in
thru the plug hole and was able to scrape up some black goo from the top
of the piston. Since the air filter was in bad shape, and it was just a
cheap ($30!) black foam filter maybe some of the black filter foam
disintegrated and got sucked into the cylinder?

The way the 3-wheeler failed was it was running great, then stalled as I
was parking it and would not restart. Did sound a bit wierd as it was
stalling but not like any heavy metal crashing.

Later today I'll hook up an air supply to the plug hole and pressurize
the cxylinder at TDC and see what I observe.

--
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