(29-06-13, 05:19 PM)Fazerider link Wrote: Have you got the inlet and exhaust cams the right way round?
Having the clearances slightly wrong won't cause the engine to jam.
It must be grossly mistimed if a valve is meeting a piston and, if that's what's happened, heaving on the crankshaft hard enough for the chain to jump could well have bent the valve unless the bottom sprocket was knackered.
Yup, the cams are clearly marked E and I, it's not the first dohc engine I've timed! :lol
You're right about the clearances, I tried it today with no shims which made no difference - absolutely locked solid from the start.
It's not mistimed, the valves are nowhere near the pistons. When timing it up, only pistons 1 and 4 are at TDC, whereas the cams are pushing Exhaust 3 and Intake 2 down.
I certainly didn't heave on the crankshaft :eek it was the lightest of pressure and it jumped, I've verified the valves are straight as I relapped them all when I received the head.
(29-06-13, 07:51 PM)red98 link Wrote: as FAZERIDER dont force it.....when aligning "t" mark on flywheel make sure the lobes on the cams on no1 cylinder are facing away from each other....that puts the engine at tdc on the firing stroke and not the exhaust stroke......saying that though if it were 180 out it would still turn over........go back and make sure the chain is seated properly on the bottom sprocket and then fit the cams again...its a bit of a fiddle but take your time and nice and gentle
Yup, that's exactly how I've done it, I've had the cams bolted in and out atleast 10 times now trying various things.
The chain is sitting on the bottom sprocket properly, it also rotates with the engine nicely with the cams removed. I tried it again today without the CCT installed. I held the cam chain up at the top, while rotating the engine, with a little pressure (still jammed) the chain rides straight off the two cam sprockets and then rotates freely.
It's definitely the topend that's jammed solid, my only theory at this point is the replacement head is actually warped, I didn't notice anything with the metal rule before I put it on though. I'm going to try again tomorrow with my old head and see if the cams rotate.
I suppose this might be why the head was only £50, with cams, buckets and shims included. For what it's worth, the bike it came off had clearly been burning oil for quite a while!
The bike's been off the road since march, and it's been a fight every step of the way, kind of gives the feeling that it doesn't want to go back on the road
