Craftsman/Murray Snow Thrower Drive Specs

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Old 12-23-07, 04:29 PM
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Craftsman/Murray Snow Thrower Drive Specs

Working on a Craftsman 11HP - 30 inch cut.

Model 536-881112.

When I took possesion of this machine it was a mess. Among other things the drive linkage was way out of adjustment. The friction wheel contact point was equidistant from the center of the friction plate at the R2 and F6 positions. This resulted in wicked fast reverse operation and virtually no forward speed.

I have no tech manual, so I just winged it and set the linkage so as to place the friction wheel at nearly the outer edge of the plate (maybe 3/4" in from the edge) while in F6 mode.

Removed the glaze on the plate and rubber wheel with some 100 grit emery. Cleaned all with carb cleaner and removed the slack in the actuating cable.

It is running much better as can be imagined. Now my question:

What is the proper static clearance between the face of the friction plate and the bearing surface of the rubber ring on the friction wheel?

And secondly, at which position should this be set? It appears that the plate is not perfectly flat with respect to the drive wheel. In other words, the clearance between the two faces looks to be closer as the wheel is moved towards the center of the disc and increases as the wheel is moved outward.

Make any sense?

I ask this because I am getting slippage at higher forward speeds and no real free-wheel effect in the reverse mode.

Could it be that the -hex shaft assembly- is not parallel to the friction disc? If not, is there a means of adjustment?

Or; is the drive mechanism designed this way for a reason -i.e. to allow for slip in case of a sudden halt at high speeds?

The components on this unit are in near mint condition and it does not appear to have been abused. Everything I have attempted to repair thus far has been done without replacement parts.
 
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Old 12-23-07, 05:17 PM
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I hope you can make sense of this without a photo. This is from an owner's manual I have for a 536.885020. The adjustment procedure should be the same.
Looking from the handlebar end, the friction wheel should be positioned 2-5/8" from the left side of the drive disc with the shift lever in first gear(forward). To adjust, loosen the jam nut on the rod, then remove the ball joint. Adjust the rod to the correct length while holding the shift lever connected to the friction wheel in where you want it. Then re-assemble.
As far as clearance, I am just guessing at about 1/8 -1/4 inch. There is no adjustment for the clearance. If it is off, you most likely need new bushing.


Originally Posted by chengny View Post
Working on a Craftsman 11HP - 30 inch cut.

Model 536-881112.

When I took possesion of this machine it was a mess. Among other things the drive linkage was way out of adjustment. The friction wheel contact point was equidistant from the center of the friction plate at the R2 and F6 positions. This resulted in wicked fast reverse operation and virtually no forward speed.

I have no tech manual, so I just winged it and set the linkage so as to place the friction wheel at nearly the outer edge of the plate (maybe 3/4" in from the edge) while in F6 mode.

Removed the glaze on the plate and rubber wheel with some 100 grit emery. Cleaned all with carb cleaner and removed the slack in the actuating cable.

It is running much better as can be imagined. Now my question:

What is the proper static clearance between the face of the friction plate and the bearing surface of the rubber ring on the friction wheel?

And secondly, at which position should this be set? It appears that the plate is not perfectly flat with respect to the drive wheel. In other words, the clearance between the two faces looks to be closer as the wheel is moved towards the center of the disc and increases as the wheel is moved outward.

Make any sense?

I ask this because I am getting slippage at higher forward speeds and no real free-wheel effect in the reverse mode.

Could it be that the -hex shaft assembly- is not parallel to the friction disc? If not, is there a means of adjustment?

Or; is the drive mechanism designed this way for a reason -i.e. to allow for slip in case of a sudden halt at high speeds?

The components on this unit are in near mint condition and it does not appear to have been abused. Everything I have attempted to repair thus far has been done without replacement parts.
 
  #3  
Old 12-23-07, 05:49 PM
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Thanks for the response but I'm confused. While looking forward - as if operating the machine:

While in any of the forward gears the wheel makes contact on the right hand (passenger?) side of the friction disc.

Moving the shift lever to reverse brings the wheel back past the center axis and to the left (drivers side) of center shaft.

Is that 2 5/8" dimension maybe from the far right edge of the disc?

This setting is not too critical - you get used to variations in speed settings. What I was really looking for was the face to face clearance with the engaging grip released.

Like I said below, I have nice tight engagement in reverse and in the lower forward range but a certain degree of slip in the F5 and F6 range.

You know what, it's probably just the conditions that I have been using it in.

Trying to clear all this snow at once - up in the White Mountains. Also the driveway is wicked steep at the top and the snow is heavy. It is most likely operating just as designed.
 
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