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Cam timing on z900 a4

Posted: Sun May 07, 2023 5:53 pm
Author: Peteypops23
:wink Hi guys,
me once again....apologies.
Firstly thanks for all the help with the z1b engine.
I was trying to balance the rebuilt carbs on the a4 and they just didn't want to play. I remembered what some of you had said before about checking everything else b4 blaming the carbs sooooooo......
Set timing mark on ignition to TDC for 1 and 4.
Took cam cover off.
Lobes pointing towards each other .....inlet cam cut out was halfway and level with head.....but...exhaust cam cut is, in my opinion, sitting too high.
20230507_152457.jpg

The cam sprocket mark is sitting a bit high too (mark at point of screwdriver) however I've counted 28 links from the one above the mark and it is fine.
Should the exhaust cam be taken out, moved to line up, then reposition the 28th pin on the inlet cam?
In my mind it should be but I just need clarification from people who know better.

cheers,
Pete

Re: Cam timing on z900 a4

Posted: Sun May 07, 2023 6:23 pm
Author: zed1015
If the timing mark is on tdc then i'd move the cams clockwise a tooth as you suggest.
It's better to have the camchain pin just below the gasket face than clear above it.
That way the timing can only drift closer to the correct timing as the chain wears as opposed to further out.
I take it that either the chain is not new or that the head or barrels have been skimmed.

Re: Cam timing on z900 a4

Posted: Sun May 07, 2023 6:44 pm
Author: Peteypops23
Thanks Rob.
I've no idea what the internals have had done to them as I haven't touched it. The chain was a bit slack but I don't think it was slack enough to jump a tooth but who knows.... and I think I'll take the adjuster apart as it didn't seem to spring when I loosened it off....
The bike was running when I bought it but couldn't take it on the road as there was no front brake.
I was going to leave a complete strip down till the end of this year.
I'll get the cam adjusted tomorrow and hopefully get it running properly :D
Cheers,
Pete

Re: Cam timing on z900 a4

Posted: Thu May 11, 2023 6:55 pm
Author: gray
I've been caught out this way on occasion - looking at your photo of the screwdriver pointing at a pin - the screwdriver is pointing at pin ZERO then start counting from there. It's NOT number 1.

Re: Cam timing on z900 a4

Posted: Thu May 11, 2023 7:07 pm
Author: gray
Another thing I have done is check the TDC mark on the points casing - using an old spark plug , with the centre knocked out and replaced by a thin +nut that will contact the piston crown. Rotate the engine forward (Gently), and note where the engine stops ( a timing disc helps here) then rotate it backwards gently till it stops again and note where it stops again. do the maths and work out the midpoint and that's your actual TDC then see how far the factory marks are out ( and grind a wee mark on the casting and a bit of paint then use that for all the timings in the future. Mine were about 2 degrees out. Then the cam timing marks will be more spot on ( hopefully)