SF top end rattle

[LaverdaDave]

My 76 SF has 90,000 kms on it.  In the last 2000 kms has developed a top end rattle to the extent that I dare not run it.  I have had the engine out, removed the head, checked valve clearances and any signs of wear.  All looks good.  OHC chain looks OK and the tension spring seems to be working as expected.
Is there something common to this model that I should be looking at?

 

[phil37]

Take the plugs out and turn motor over by hand. If there's a clunk momentarily after you stop turning it will be a cam loose in its flange. Could be a million other things of course - regards - Phil

 

[breganzane]

Usually the camshaft keyway.  It's not so much the keyway, but the fit of the flanges on the camshaft half.  Some searching the archives should give you plenty of info.
Cheers
SteveB

 

[mikeringrose]

Hi,

My 750 SF1 developed a rattle in the top end. Having taken advice from this forum I took the cam covers off both sides of the head and removed the spark plugs. Then with my mate turning over the engine slowly I put a finger from each hand on the ends of the cams. There was a noticeable click and jump of the cam which confirmed the flange was loose.

Even though you can buy flanges cheaply, the cams are expensive. I found an engineering firm who could metal spray and machine the cams to the right size to fit the new flanges which saved a lot of money. I have the details of the engineer somewhere if you need it.

I could not help go through the top end in detail looking for worn parts. What I thought was a small repair job cost me ?600 in parts so brace yourself. And the pistons were OK!

Kind regards
Mike

 

[phil37]

I bought a cheap DIY nickelplating kit and salvaged a pair of cams by plating the ends. Andy wagner does different size flanges - also a flange with clamp is available - Regards - Phil

 

[Tippie]

And any decent machine shop could spin you up a pair of flanges with correct interference fit to your cams.

 

[piranha-bro2]

Does sound like cam flanges - once they've been off and on a few times the press fit loosens. Easy fix - definitely doesn't require new cams. I had an undersized crank journals on my (SFC!!) crank! Bearings would fall on by hand. Had them hard-chromed and reground - prob solved.

I have also pulled my crank apart after hearing knocking in the bottom end, fears of bad things, but mainly suspecting cam flanges - found out it was a loose splined drive on my ND alternator conversion!! Very difficult to pinpoint the source of noises - you should see the dramas alu bicycle frames can create - acoustic nightmares.
qf