Tight camshaft

[shaggy]

Hi am rebuilding a 75 Z1B engine have put new camshaft bearings (supplied by z power) in but when I bolt down (with no valves fitted )the exhaust camshaft spins freely but the inlet is as tight as a ducks chuff and doesn’t want to turn any ideas why as the word camshaft and valves are foreign to me as I mainly work on simple 2 strokes.

[Al]

Are they repro (OEM) versions that they sell or genuine ones that they also sell?

AL

[warren3200gt]

Make sure the shells are seated on CLEAN castings and are CLEAN and lubed before dropping in the camshaft.
It would only take a tiny bit of muck to lock up rotation.
Plasti guage will help you determine if its just one shell or all four pairs.

[Gray17]

Just going through similatr process with my cylinder head, when i first put exhaust one back in ,(no valves) using original bearings in original positions it ran fine and easily turned, however when i put the inlet camshaft back in agsin in original positions it was ok until i tightened up the bearing caps, then was really tight to turn. So i first removed 1 bearing cap leaving the other in place, it was still tight, so then i knew problem was the other one which also has the thrust bearing. I removed this and there was a very slight sliver of aluminium under 1 of the shells, removed this and all perfect.
They are very close tollerence doesnt take much to tighten it up.

[zed1015]

Is this with the head on the bench or bolted to the block ?
You need to be aware that these heads can have a slight twist in their free state which can bind the cams when on the bench.
This usually pulls straight when bolted down.
If that is the case you must bolt the head down to check the free running of the cams.

[shaggy]

At the moment head is on the bench when cam is bolted down but not torqued cannot turn by hand even if I loosen either cap but exhaust spins nicely.
Have put the old bearings back into there respective caps and still it won’t move?

[zed1015]

As stated. if the head has a slight twist the cam or cams will bind when fitted on the bench.
You need to bolt the head to the block to pull it straight and then test the cams for free running.
I've never had cams bind in a head once it's bolted down.

[Gray17]

Hi Rob, wasnt aware of the twisting and perhaps I've been luckier then Shaggy has. Before stripping mine i never checked as it had all the valve springs in place so impossible to tell, however as im setting up the valve clearences ive not put the springs back just bare valves to confirm clearences. Both of my camshafts turn perfectly and smoothly with no binding at all. I can only summise either my head is perfectly flat after the machine work done and all camshafts bearings perfectly inline on the bench. Of course unless you put the head on and then torque it down with head gasket but without valves and springs which you wouldnt normally do you would never know if camshaft rotates freely.
Im now concerned mines the opposite ie if Shaggy bolts his down to correct torque his will then turn freely, when I bolt down mine it could tighten up? I will check when i get that far, as stated when i 1st did it mine tightened up too but it was something under 1 of the bearings, so worth checking just in case.
Struggling with my spring compressor at mo as it allows collett fitting on outers but binds on inners ie it doesnt compress spring enough before it hits the edge of cam cover surface. They all came out ok though?
Ordered a different type online awaiting its arrival.

[zed1015]

Im now concerned mines the opposite ie if Shaggy bolts his down to correct torque his will then turn freely, when I bolt down mine it could tighten up? .

No! If the cams turn free on the bench it's not warped and gonna be fine once bolted down and a warped head should be pulled true once bolted down and again be ok.
Any "adjustments" that may be needed to rectify a binding cam if still required should be done with the head bolted down.
The danger is in taking an unchecked head that has a slight twist or bow when off the bike and having it skimmed flat..
This will retain the discrepancy on the cam journals when the head is fitted and then you get problems with journal clearances and overheating of the shells and cam etc.
I always check that the cams spin free on the bench before having a head skimmed.

[shaggy]

I have a spare set of camshafts tried one of them and not so tight the first one I tried has a number 2 on it the one I’ve just tried has a number 5 on it what do the numbers mean?

[zed1015]

Just batch/manufacturing codes .
All Z1 though to mk2 are the same profile and timing.
Have you bolted the head down as advised to check ease of cam rotation.
If not you are wasting your time.

[Gray17]

Ok so my camshafts rotated fine without valve springs in place on both inlet and exhausts. I have now re fitted all of the springs etc to the head, gave it a good dousing of oil on all of the needed surfaces and cam buckets. The cam shafts feel very tight now, how tight should they be when under spring tension?
I can put a flat screwdriver at eaither edge and it will move a mm or so which is the end float on both, i can also using a screwdriver move the cams. I wanted to re check the valve clearences before fully fitting the head. But dont want to damage anything.
Should it be this tight or as per Shaggy issue, has it now tightened them up due to spring pressures and needs clamping the head down onto the block to restore the rotation to normal?
Dont want to get it all clamped down and find its ot right.
Thanks

[zed1015]

Ok so my camshafts rotated fine without valve springs in place on both inlet and exhausts. I have now re fitted all of the springs etc to the head, gave it a good dousing of oil on all of the needed surfaces and cam buckets. The cam shafts feel very tight now, how tight should they be when under spring tension?
I can put a flat screwdriver at eaither edge and it will move a mm or so which is the end float on both, i can also using a screwdriver move the cams. I wanted to re check the valve clearences before fully fitting the head. But dont want to damage anything.
Should it be this tight or as per Shaggy issue, has it now tightened them up due to spring pressures and needs clamping the head down onto the block to restore the rotation to normal?
Dont want to get it all clamped down and find its ot right.
Thanks

That's normal, there's nothing wrong as long as the cams rotate freely in the bare head with no springs etc.
The resistance you feel now is just spring pressure.
Don't fit both cams at the same time to the head on the bench though and make sure the head is spaced clear of the bench surface.
You risk tangling the valves and bending one or two.

[Gray17]

Thanks Rob, yes they did rotate freely without the springs. Yes i did wonder about the valves hitting each other, will do as you suggest 1 cam at a time and check tollerences, i did as you suggested and left them on the loose side knowing theyl tighten up once running. I'd rather have a bit of rattle then a burnt out valve if too tight.
Incidentally i tried to use my sykes pickavant valve compressor, got all colletts off ok, but it would not press valves springs far enough to re fit. So i bought a cheap kit of ebay you get a u shaped handle with a thread on each end and some diff sized units that clip on and compress the springs. Didnt look that good or strong, however have to say it worked perfect and whilst not as substantial as the other one, and you had to wind it on and off rather then a locking motion.
Its worked great.
Im looking forward to getting engine back together as heard if you leave crankshaft bearings too long they can rust? I did oil them before re fitting so hope ok.
Ill keep you all posted.

[shaggy]

All now good with head bolted down