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1967 18 HP Fast Twin magneto cam question

H

Hoopy Frood

New member
Hi all,

I'm trying to get the above motor running for my grandson. I've broken two magneto cams, and I think it's due to tightening
the magneto down too strongly.

It appears there's nothing under the magneto cam that would prevent it from trying to move further down the crankshaft end.
And since the end is tapered, that causes the cam to break. Am I correct in this, or is there a piece missing that goes under the
cam? The torque is shown to be 30-40 ft. lbs.

I've been using a cordless drill motor to spin the engine over and I think when I do that I apply too much pressure to the cam,
and it breaks. Is my thinking here correct, and I need to stop doing that?

The compression is 120-125 PSI in both cylinders, new spark plugs, cleaned the carb. Big fat spark before the cam breaks. So
I'm thinking it should start if I can keep from breaking the magneto cam.

Thank you for any advice or condemnation. :)

Howard
 
Perhaps it was overtightened and expanded the taper in the flywheel.----Try another flywheel.-----No idea why anyone would use a drill to turn a motor over.----A magneto in good condition does not need that treatment.
 
racerone said:
Perhaps it was overtightened and expanded the taper in the flywheel.----Try another flywheel.-----No idea why anyone would use a drill to turn a motor over.----A magneto in good condition does not need that treatment.
Click to expand...
Yes, I'm sure it was overtightened. Completely my fault, but I had thought the cam bottomed on on a edge, not just the taper on the flywheel.

I'm old, :), and don't have the muscle to spin that motor over half a dozen times to get fuel to the carb and see if it will start. With the 120 psi of compression, it takes some oomph to spin it over.
 
Maybe the recoil rope is the wrong length and the recoil is not timed correctly.----When it is timed correctly it may be easier to pull over.
 
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