750 camshaft assembly

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lavfancier

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Hi - can anyone offer advice installing/aligning the flanges on the camshaft on an SF750 motor?
It's a long time since they were disassembled for replacement of the bearings and I can't for the life of me remember if the flanges were a press fit or a clearance fit on the camshaft.  Mine seem to be a press fit and its proving very difficult to align the key-way without damaging the key- maybe the  key is a little distorted or I need to make a new one? Any tips/advice greatly appreciated.
Cheers
LF
 
LF, when i did mine ,they were tight too. So i ended up putting the cams and key in the freezer and warmed the flanges on the heater. They went together quite nicely then, just pulled the two together by tightening the studs.
Hope this helps.
Al
 
Thanks for the reply- problem I have is that when I assemble/align one of the cam half's the key is pretty firmly stuck there- maybe I'll make up a new slightly smaller version - can't be too loose though as I'll loose alignment.
LF
 
It is good that your flanges are tight (should be assembled in a press), it is a problem with SF that after removing a few times they can get loose in operation (undersize flanges are available if they are not tight enough). It should be simple to align the keyway holes on each piece, press barely on and check/adjust before continuing. The key often has burrs after use, I carefully file these off, then carefully tap the keyway into one side of the assembled cam half. The other half will slot in when you put the cams together in the head. From experience the two halves can be knocked together easily with a plastic tipped hammer before tightening with the studs. It should not be a problem if it needs to pull with the studs the last little bit. I always use a heatgun and preheat the head to warm touch with a bare hand so that the bearings go fairly easily but not the cam flanges before pressing onto the cams. Check that the cam bearings are C3 before you fit the flanges.
 
The key can also be cut in half, aids assembly enormously. 

The cam halves are held together by the press fit in the flanges and contact pressure to the chainwheel only, the key is for location only and will not transfer any forces.  Fit each half in one cam/flange assembly.  Not too good to pull the halves together with the studs, Tippies tip with the heat gun is spot on, only need a few degrees to get the cam bearings to slide through the casting quite easily.

Flanges must be a tight fit on the cams or problems soon arise!

piet
 
OK,
Finally got it all together but flanges are close sliding fit, certainly not what I would describe as a press fit.
I guess this one has been apart a few times-I think my main problem getting the component parts together and aligned was due to burrs pushed up around the keyway slots in the cams, after I dressed these it went together OK however I'm a little concerned over the fits now.
I'll pull it back apart and apply some 648 to the flanges- anyone tried this or do you think I need to make some undersized flanges?

Thanks again for the replies chaps.
LF
 
Find yourself a set of tight fitting flanges.

Van Dijk has flanges that incorporate a pinch bolt for this purpose.  Can get a set for you beginning of March when I visit him.

piet
 
Thanks for the offer- is there a lot of history of the cams slipping/shearing the woodruff key?
LF
 
lavfancier said:
Thanks for the offer- is there a lot of history of the cams slipping/shearing the woodruff key?
LF
Click to expand...

You gotta be joking!

Seen it dozens of times, especially while these bangers were run on a shoe string.  Seems to be less these days, owners are more aware of certain problems and have the skills/time/money to rectify before havoc breaks loose.

piet
 
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