Magento mystery 71 9.5hp

[Greg O.]

I bought this 71 9.5 a couple of years ago on a boat. It didn't run very well so I set it aside. I could not get it to idle even after cleaning the carb. This winter I decided to make it run as it does have good compression. I decided to start with the mag and get it tuned up. The plate has some play in it so I took it off to see what I could do to tighten it up. Underneath the cam someone had put 8 snap rings to shim the cam high enough so it would engage the crankshaft key. The snap rings are riding on the seal, not good. What is missing here? Do I have the wrong cam and the tried to make another one work?

Another idea I had was to abandon the points all together and replace them with those electronic module that are made for small engines. I used one in a chain saw and it worked great.

 

[Greg O.]

No Title

Snap rings underneath the cam. I do not like the fact the snap rings are riding on top of the seal. The only part I see between the cam and the seal is an o ring. I assume it is inside the crankcase.

 

[Greg O.]

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the cam rides to low to engage the key without shimming ( the snap rings )

 

[F_R]

I don't have a clue. But I wonder...has somebody cut the cam to make it shorter? Maybe to compensate for a stretched flywheel taper on some other motor?

 

[boobie]

Get the original cam and try it.

 

[boobie]

You may also want to get the original flywheel key from a BRP dealer.

 

[Greg O.]

Thanks for the imput. I am thinking it might be the wrong cam, as there are no markings on the cam, or it has been cut.

 

[Greg O.]

I just looked more closely at the cam. It is obvious one end has been cut. There are no markings and the edges are very sharp. The jaw marks from the vice are even visible in the sides of it. The taper in the flywheel looks fine as well as the shaft. And the flywheel seems to sit properly on the shaft. So I bought a used cam from ebay. Stay tuned I will see what happens.

 

[F_R]

So, that was a lucky guess. Anyhow, the usual scenario there is that somebody will overtighten the flywheel nut (Impact wrench ?), which forces the flywheel down on the taper, expanding the hub. It also goes down far enough to break the cam. So, it would seem that some genius cut your cam to compensate for the lower flywheel. What we don't know at this point is if all that happened on this motor or another. I don't think you can tell about the flywheel taper simply by looking at it.

BTW, the proper torque on the flywheel nut is 40-45 foot pounds. Very important as just proven.

 

[Greg O.]

Thanks FR. When I get the new cam, I will have to do some measuring to see just where the flywheel sits. I think I could use some Prussian blue or something like that to leave marks. Of course all of it would need to be cleaned off the taper before final assembly.