SOHC.co.uk Forums > CB750

Help! What's caused this?

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Bristolbadger:
Hi folks, I'm properly gutted after I finally finished my k3 750 sohc, got her MOT'd and finally on the road and driving sweet. After 30 or so fairly gentle shakedown miles I decided to pop the cover and check valve clearances and re-torque all the bolts... only to discover the cam seemed off centre on the right side holder...
Low and behold the horror in the pics! I'm mortified to say the least after 2yrs of ground up build.

What could have caused this? Only a bent camshaft that I can think of as I did a full bench check to check oil circulation to the head and all metering jets were clear and oil was getting up to the journals and everywhere nicely. Was getting good running pressure with a gauge attached to the pressure sender initially and also no oil light warning (yes the pressure switch is working) when I was riding it with that back in.

The left side cam holder/journals and camshaft are fine and unmarked as was everything up there when I assembled the engine.

I can't vouch for the straightness of the camshaft when I got the bike so I guess its possible the cam had been dropped or bent and I just had a dodgy one to start with.

Not sure my best course of action now?
 I'll strip all the parts off and take the cam fully off and investigate for any further damage I guess but then best case scenario is me left looking for a second hand camshaft and right side holder and journals. F**k f**k f**k!



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Bryanj:
That was caused by crap blocking the oil jets, did you use silicone goo on the crankcase?

K2-K6:
As above, classic head feed oil passage impeded (there's one for each side of the head) and consequently oil starvation.

You can see the heat range on the rockers as they've over heated too without oil.

sye:
I have no idea what caused it but it's bone dry. There should be oil everywhere.

K2-K6:
Certainly feel for you, it's horrible putting in all the time and effort to then get a failure like this.

It won't show on the pressure guage or oil light as even with this route completely blocked they will look ok.

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