Crank bearing inside the Mag plate M engine

[old servi]

Do you have the thickness size of the bearing that sets in the Mag plate on the M engine. Bearing is on the crank and just back of the point breaker cam. This bearing is thicker than the bearing for the H engine. Or better than that, the bearing number.
Thanks for your time.

[Ricks]

They used 2 different bearings.  Both are 40mm OD x 17 ID.  One is 12mm thick, the other is 17.5mm.  I run the 17.5mm size in both of my model m engines. I just disassembled a late Model M on a sportsman that used the 12mm bearing.  My two that used the wide style are wico while the later is a phelon.  To be honest, I don't think it matters as the difference is taken up by the spring.

Part numbers:  40x17x12      6203
                     40x17x17.5   5203

I buy my bearings here:  http://www.thebigbearingstore.com/index.html

I try to buy them in advance and keep them at home to save the shipping charges.  Sucks to buy one bearing for $3 and pay $10 to ship it!  I usually keep a couple sets of main, rod, and stator plate bearings, as well as transmission bearings in stock for the next project!

[pd]

"To be honest, I don't think it matters as the difference is taken up by the spring."

Rick ,

From what I read in the manual , only the Wico mags have the spring .
My Phelon mag had no spring , nor was there any room for one .

[Ricks]

"To be honest, I don't think it matters as the difference is taken up by the spring."

Rick ,

From what I read in the manual , only the Wico mags have the spring .
My Phelon mag had no spring , nor was there any room for one .

Ah, have you ever disassembled a sportsman engine with an internal kickstart? It has a spring, but I'm not 100% sure it was supposed to!  Other than that, I have no experience with the phelon mag.  What size bearing is in yours Pete!

[Mike Sal]

No spring on my phelon equiped bike.  Rick what does the spring bear against on that late motor of yours?
Mike Sal

[Ricks]

"
Rick ,

From what I read in the manual , only the Wico mags have the spring .
My Phelon mag had no spring , nor was there any room for one .

Pete, I just went to the manual, and the spring is listed under the engine parts section and not the magneto section.  It doesn't make a distinction between the 2 different types!  Interestingly, it lists 2 different part numbers for the breaker cams!  I need to see if I have a spare Wico one laying around to compare it to the Phelon.

I like a good mystery!  Anyone else have some input on this?

[Ricks]

No spring on my phelon equiped bike.  Rick what does the spring bear against on that late motor of yours?
Mike Sal

It goes between the cam and breaker plate bearing, just like the drawing in the manual.  As we all know the quality of the build of that motor, I am NOT sure if this is correct. I suspect it may have been added to take up the space between the narrow bearing and cam gear, and it appears to have been cut to about 1/2 its original length.

On the Phelon, is there anything between the cam and breaker bearing?

[Mike Sal]

Hmmm....The phelon cam is held in it's location by the flywheel woodruff key.  A spring would be trying to push the bearing closer to the motor& not let it float I guess. 
Mike Sal

[pd]

I don't know which bearing is in there , Rick . I thought I might have written it in my shop notes , but nothing .
The mag bearing is the only bearing I didn't replace on the whole bike .
From what I could tell the installed bearing was/is still good . No side play or 'wobble' and it spun cleanly with little effort . So , I left well enough alone .

Good that you posted the sizes and numbers , in case I ever need one and can't read what's stamped on the bearing I have .

I want to pull the motor apart , again ... when I do , I'll see if I can see a number on the mag bearing ( might be a while before that happens , so don't hold your breath ) .

[pd]

The Phelon cam is directly against the bearing and held from spinning by a key , as Mike said .

In my 'M' manual , the spring : #189 - Breaker cam spring ( only with Wico magneto ) .

From earlier observations , I noticed that the Wico and Phelon magnetos are positioned about 90° different . That would demand that the cams also be 'slotted' about the same difference .

[Mike Sal]

I forgot to notice how close the bearing was to the cam on mine.  I didn't replace my bearing either as it was in good condition.

Pete, why are you wanting to take the motor apart? 
Mike Sal

[pd]

Mike ,

I'd like to take the motor apart to check ring to cylinder wear . But mainly , I'd like to see about making a sleeve that fits snugly inside the intake throat and reduces the clearance between the crankshaft and throat opening .
I'm thinking that may increase fuel transfer efficiency and improve overall performance by helping to eliminate back flow during the down stroke of the piston .

That or maybe mount a reed valve between the carb and case , but that just seems a bit redundant and more a patch ( less original ) .

[old servi]

Thank you for all the information on the bearing. I bought the engine and the guy that advertised it said it was a great
running engine. He had if overhauled by a specialist on small engines.
Yes he did?
There is no bearing at all on the mag plate. just blank space between the cam and the belt pulley.
I thought is should have a bearing there but the space is thicker on the mag plate than my H engine plate.
Is there a set screw on the M to hold the wide bearing in place as it is on my H?
Ricks, thank you for the number to use on the bearing.

[Ricks]

No set screw. There is a spring between the bearing and cam.  Check the 1960 manual in the manuals section for a picture.

[pd]

old servi ,

Just to satisfy my curiosity , which magneto does your M have ? Wico or Phelon ?

Rick or ,

Which years did Simplex use the Wico and which years the Phelon magnetos ?

Pete .