Z900 Valve Clearance issue

[Gosling1]

OK fair enough - on a job like this, I would have replaced the inlet guides & valves as well.......and it looks like the seats will have to be done anyway ? Its worth the coin in the end, because once you have done all this, you should only need to re-set the valve clearances once more in 6 months time (assuming the bike is ridden every week ) - and then you can basically forget about the clearances......

[Sulli]

ok thanks for the last pic tells a good story the top valve in the pic see the black ring on the 45 angle thins a bit on the side facing if this black mark goes around the whole valve face the valve is good It will take more time than I've got atm to guide u through the hole process
do not dispose of those valves as they could be a cheap fix for ur issue

[Angry Emmet]

Thanks Angry - I dug my book out and got all the specs so I'll take that with me in the morning. I have a bit more confidence this bloke can help me out. Cheers for the tips i will keep all of that in mind.

Gottah love that this is stirring up some really interesting discussion. Thanks all.

No probs mate. By the by, a head doesnt/shouldnt be machined on gasket face unless its not "flat" or is burned etc from gasket failure, heads have a min thickness and lots of them cant have much taken off, for instance XJ6 Jag cant have more than .005thou from memory, WRX is 12 thou max etc.

Your VALVE STEM HEIGHTS SHOULD BE BETWEEN 37.77-38.07MM, you really want 37.77 max. By the look of your exhaust valves they have not been "tipped" and would be way too long, your inlets will be too long as well. If you dont want new seats (cant afford etc) you can take some off the collet, down to just above cap surface BUT must keep stem tip surface above that for the bucket to push on, you bucket has a raised section in middle under to push on stem etc (shim on top buckets). You might, when doing this, end up less than 37.77mm, if your going a lot under I would do seats. Measure all first, that way can save your valves, fit seats and start again. Bonus is that new modern seats are a LOT better than O.E. 70s Kwaka seats. Good luck with it.

A.E.

[aggerz]

Well I took it down to mates workshop he measured up the valve heights and yep they were all very high, I don't have exact measurements on me but they were either just on max or over spec

He said at a glance the seats don't look surprisingly too bad but did say there had been a bit of butchery as the valve seats don't look like they've been cut just lapped but are rough as guts so he'll try clean that up as much as possible without taking material off and see where it leads us however in other news the inlet valve faces are all pretty thin (Below spec) they should never have been refitted so hes recommended we replace those.

So once I get the new valves we'll get it all together again and look at the measurements, at this stage looks like seats can be saved and tip the valves and right to go but if I have to do seats after all this so be it. The bike was my dads from new, so it has unlimited sentimental value and I want it done right.

Also, the dark ring around the combustion chambers on the face is actually a a noticeable low point around 2 of cyls, you can feel it with your fingernail so he wants to ever so slightly just skim and see if we can clean that up.

Cheers.

[s man]

Just dock the top off the valve stems to get enough to fit the shim. We did it in the old days. In fact ive done in on my racebike with a 5 angle cut. Works fine.

[Sulli]

Just dock the top off the valve stems to get enough to fit the shim. We did it in the old days. In fact ive done in on my racebike with a 5 angle cut. Works fine.

yes that's a good solution in this case if you know someone with the knowledge to do it correctly How ever Aggers mate appears to be on the ball unfortunately it won't be cheap but it will be a better spend than the last $600 all the best with the project keep us informed

[Sulli]

Also, the dark ring around the combustion chambers on the face is actually a a noticeable low point around 2 of cyls, you can feel it with your fingernail so he wants to ever so slightly just skim and see if we can clean that up.
Cheers.

Check the tolerances as this was common as the head gaskets had metal rings for this purpose also correct tension of the head to the block was often overlooked and re tension after heat cycling the motor was unheard of

[aggerz]

Ok. Thread grave digging time.

Just an update .. When I last left this thread I'd already ordered some new valves and seals from Z1 Enterprises (love these guys!) but thanks to a little muck up it got shipped Priority not Express like I asked AND somehow ended up in Mexico for a few days and then when it arrived sat in customs for another 4 days!! When it finally landed on my desk this week it had an Austpost label on it for "HEAVY - BEND KNEES" ..the box weighed barely 1kg.

Whilst this was happening I also managed to score some cheap shims from a wrecked bike on ebay US so we got plenty to play with.

I got our work courier to drop all the parts off at the workshop for me, he rung today saying the head is all good to go, I don't have the list of everything he did to it but he did say that the clearances are perfectly in spec now and ready to bolt back on. I'll find out all the nitty gritty when I go grab it - stay tuned - I can't wait!

[Gosling1]

sounds good mate, looking forward to more updates on this rig as you go.....

[Strika]

I posted up a long post on my phone and it appears to have been lsot in the ether. In a nutshell, I suggested going back to square one and just doingthe head up completely while it's apart. I know it's exxie, but having new seats, guides, seals, valves, collets and retainers will make sure it has enough life left in it that you won't have to pull it apart ever again!!!