SF750 cams

Fitz

Fitz

Senior member
Location
Cheshire UK
More questions FFS

I was setting about getting parts ready for rebuilding the motor of the SF, I have new camshaft bearings, easy enough to replace while it's apart so why not

I am not happy about the discolouration of the cams. They have a peculiar wear pattern but there are no burrs and the surfaces look quite good apart from what looks like a chrome surface treatment that has worn though. There is no ridge or edge to the wear marks, I can also see evidence of discolouring but that may be when they were manufactured and heat treated

Everything else I have found ties up with the engine and chassis number identifying the bike as a 1971 SF model, I am assuming these are standard cams as I can't find any marks on them

Any comments please or recommendations for refurbishing them (NW UK)
 

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The cams look fine to me. I always polish them up on my cloth metal polishing wheels to make them as smooth and slippery as possible and do the same on the rocker arm surfaces. Slipper rocker arms are very dependent on good oil supply, make sure there is nothing impeding it.
 
If they look slightly scored, I also smooth my cam lobes and rocker surfaces with very fine emery paper then polish as per Tippie's suggestion. I doubt that would be hardchrome plating on that cam lobe - the rockers are hardchromed and you would NEVER  run both together. Making sure they get as much oil as poss is the key to a long and healthy valve train life.

Interesting there are no markings on the cams - my SF1 was the same, even tho every year model has its own numbered cam profile but I would have thought yours was 4S (could easily be wrong).
 
Stamping 750 cams commenced somewhere around 1973 I would guess. Everything before that was unstamped.

Marnix
 
Thanks all, very reassuring

Has anyone had any issues pulling the gearbox sprocket. I removed the locking washer without a problem but the sprocket does not appear to have splines. It may just look that way after so long on the bike but it looks like the splines on the shaft have been undercut and removed

I tried a little pressure with a 3 jaw puller but don't want to force anything

I want to change all of the seals so one way or another, it is coming off, i'll take some pictures if I cant get it off this morning
 
Do you mean the sprocket for the chain to the rear wheel?

Cheap trick if your sprocket has the normal two M6 threads and you have no puller:

Solution A
- Take a metall plate min. 5 to about 15 mm thick with dimension about 80 x 120mm.
- drill two 6,5 mm holes coresponding to the two M6-threads in the sprocket.
- Place the plate on the shaft stub and look for two M6 screws that are long enough that they go straight through the thread in the pinion when screwed tight.
- Now alternately tighten the screws and carefully tap the screw head alternately.

Optimized variant B:
- Drill an additional 10.5 mm hole exactly in the middle of the metal plate.
- Weld on the outside an M10 nut exactly in the middle, if possible with a fine thread, to the metal plate.
- Screw a suitable M10 screw into the thread and place a thick washer or flat steel between the screw end and the shaft end so that the screw can support itself there.
- put oil to the thread and the contact-points
- Now tighten the M10 screw and tap the screw head briefly with the hammer.

This will bring the pinion safely off the shaft.

I hope Google's translation is reasonably understandable ...

Thomas aus LAU
 
I use the item in the pics as a puller support.
My friend made that on his lathe.
Has done the job several times.

Ernesto
 

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3-jaw puller works for me - as per other post put something in the hole to centre the puller threaded shaft and protect the gearbox output shaft. getting them back on is the tricky bit! whacking them onto the splines with a big fat hammer is NOT the way to do it - can force the output shaft inward and the retaining ring could damage the cases.

There are tricks in the forum somewhere for getting them to behave ... like chamfering the inside edge of the sprocket (or summit like that).
 
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