Cam bushings and washers

Joined
Apr 15, 2004
Messages
1,616
Country flag
I'm starting to put my motor back together and I'm a little confused about the cam bushings. This motor started out as a 1971 750 but was rebuilt with a set of 1972 cases at some point in the past. It has a scrolled cam, unscrolled bushes, and the chamfered thrust washer. The drive side bush is flangeless, the timing side bush does have a flange.

So what is the proper configuration of thrust washers, shims and bushings? And how much endplay should there be? I have another '72 motor on the bench. Its cam endplay is .032 inches with the sprocket in place and the nut tightened. That seems excessive to me but what do I know? I haven't split the cases on that motor yet so don't know what's inside for thrust washers etc.

I've read Fred Eaton's article about the bushings but it leaves a lot of questions unanswered, at least for me.

thanks,
Debby
 
Joined
Dec 5, 2003
Messages
287
Country flag
Debby

Let me see if I can help;
Scrolled cam and unscrolled bushes are OK just make sure the oil feed holes line up.
I guess the first question is "are the cam bushes new?" If they are new then they will have to be reamed to size. You will probably want to farm this out to a shop that has done this before since the cases need to be bolted together to properly line ream. If you are going to use the existing bushings do a dry fit of the cam and thrust washer and bolt the cases together to check the end play and to see if there is any up or down movement on the cam or if there is any binding when the cam is rotated. if you get either one of these you might as well spring for new bushes now cause it ain't going to get better. End play? hmmmm. well .032" sounds like a lot but I suppose the cam chain will tend to center the cam as long as the lifters are square to the lobes. I would probably like .010" better but maybe someone else has a more definite idea whats right. The shop manual has the spec for limits on cam bearing dimensions and bush bore size so you may want to mike them both to see if they're OK.
I don't think any of this is all too critical but since you've gone this far you might as well make it as close to right as possible. I suspect the cam flexes a little when running so having everything lined up and properly supported makes good sense but it would still work even if it wasn't perfect.
BTW did you get a new cam? Stock or otherwise?
Keep the faith and good luck,

Scooter
 
Joined
May 7, 2005
Messages
5,950
Country flag
Dynodave posted this a few days ago on Britbike about camshaft end float,

With the cases bolted together AND the sprocket/nut on, you will have about .015-.030" end play. This clearance is basically the same for all norton heavy twins.
 
Top