Z900 Valve Clearance issue

[aggerz]

Hi All,

I Need some more advice from the experts out there please.

Still in process of getting motor back together (76 z900a4) I sent the head off to get reco'd while it was all apart, now come time to put it all back together I've put it on, torqued up, cams back in and I have ZERO valve clearance on any valve.

It's no surprise that the valve clearances needed doing but I guess I didn't expect to have no clearance at all on any when it went back together.

For example, Exhaust #1, current shim 265 , I went to a Dealer and picked up the smallest they had (215) and I still have no clearance (using a .038mm feeler gauge)

I would have thought by dropping to a 215 surely I would have seen some sort of improvement but it appears not, So should I find the smallest (200) and try again? or is there some other issue at play here? Would the reco really bring it back to requiring only a 200 shim?

And if I do get a 200 and it still doesn't fit what are my options, was the head done wrong?

Sorry for the maybe basic questions but I'm no bike mechanic just someone trying to take their time and learn the process and wants to get it right first time.

Thanks for your help. Cheers.

[Gosling1]

what did they actually do in the *reco* ??

Machine the head surface ? How much came off ?

Replace valve seats ? What brand did they use ?

Replace valve stem guides ? What brand and what deck height did they set the guides at ?

There are a lot of reasons that clearances can be nil, but the smallest shim you can get is the 200. If you cant get any clearances using this shim size, then your next option is to *tip* the valve stems.......but be careful doing this, as you can really only give these a slight touch-up - if you take too much off the tip of the valve stem, you won't leave enough meat on the valve so the valve-keepers can seat properly - this will cause problems with the valve springs.....

I would talk to the mob that did the reco, and ask them some questions about the valve stem guides.........and the valve seats. Did they actually get *replaced*, or did they just get a 3-angle valve job ? If this was done with a bit too much enthusiasm, you will lose a lot of adjustment clearance right there.....

[Angry Emmet]

In the Kawy workshop manual there is a dimension measurement that gives minimum and max distances for valve stem height above the valve spring height, this should have been set by the machine shop BEFORE assembling the head, ask them if they did it. If they didnt you will need to pull the head again, dont worry,you havent started it so the headgasket will be ok, be careful not to disturb the barrel, you might like to make some spacers (or use appropriate half inch drive sockets) to slip onto the studs after removal of head, put spacer on and clamp down finger tight with nuts on studs. I have been caught with this before, even after telling them to make sure measurement is correct....AND giving them the bloody measurement itself!
ARE YOU SURE you are checking clearances with lobe pointing upwards? Its called "lobe away method", means lobe is pointing directly AWAY from the valve stem tip, not directly vertical but directly away from valve stem, for example, exhaust will point upwards and slightly towards the front, inlet will point upwards and slightly to rear etc. Dont panic yet, just double check it first, its part of the game unfortunately. ALSO, if you are fitting new cam bearings get the head back off them if pulled apart to tip the stems and fit up your bearings and cams and check the bearing clearances with plasti gauge to make sure clearances are within specs. ONce head returns you can fit up a cam at a time on the bench, check your clearances,even adjust them, WRITE IT DOWN which shim goes where. THEN pull cams and fit the head again etc. MAKE SURE everything IS SPOTLESSLY CLEAN WHILST YOUR AT IT!

Cheers.

[aggerz]

Thanks for the replies so far I'll answer what I can

The head work was done best part of a year ago, I only just got around to unwrapping it and putting it back on so I am not sure what sort of information if any I will be able to get from who did it (3rd party, a bike shop sent it off). The person I'm told had done many of these heads before and reckoned for whatever its worth all things considered the head is in pretty good shape compared to others he had seen.

I don't have a specific list of the work performed, but ALL valve guides were replaced as well as 4 valves (i got given all the old parts back, no idea of brand fitted) The surface was only lightly machined from what I can tell, no specs on material removed couldn't be much.

There was no measurements (that I have) taken before the work was performed (other than shim&bucket location - i have installed these back as they were of course)

- New cam bearings have been fitted.

I will double check the lobe angle that I have when checking the clearance but without going out there right now (too cold!!) it sounds consistent with the approach I'm taking.

Thanks for the tip re using sockets as sleeves.

Sounds like overall this going to take a bit more work than forethought Thanks for the help and suggestions I'll start digging for more info tomorrow and see what I can turn up.

[Strika]

All other things being equal, it sounds like they havn't put new seats in, but rather refaced the seats.

[Sulli]

last time i did this I just set them the whole unit cams head valves told them to regrind the cam to race specs and fit they tunnel bored the cam bearings and fitted new bearings set tolerances. The valves were ground an seats replaced if necessary and reset heavier springs were put in this was at the request of the engineer , so he could warranty the job very professional shame he is out of business now bty all clearances can be done on the bench

[aggerz]

Thanks for the help all. I agree the seats appear to just be refaced than replaced.

I pulled the head back off again tonight, going to take it down to an engine builder mate see if he can help measure up a few things for me.

Few pics attached FYI.

I noticed that all the Exhaust valve stem protrude a noticeably past the retrainers whereas the Intake stems not much at all (All Exhaust valves are brand new)

INTAKE


EXHAUST


VALVE FACE


CLOSE UP

[Strika]

Gotta be honest, any machining shop which can't work out that there is no meat left on the vavle seat, needs fuckign up the arse with a pineapple!!!!

[Angry Emmet]

[quote="aggerz"]Thanks for the help all. I agree the seats appear to just be refaced than replaced.

I pulled the head back off again tonight, going to take it down to an engine builder mate see if he can help measure up a few things for me.

Few pics attached FYI.

I noticed that all the Exhaust valve stem protrude a noticeably past the retrainers whereas the Intake stems not much at all (All Exhaust valves are brand new)QUOTE

Cant see your pictures. BUT, here is a tip, MAKE SURE you get the correct tolerances to your mate to measure, I can dig thme up if you dont have a manual. YOu may not necessarily have needed new seats BUT if their old it is best. Now, the valve stem can be ground down until just above top of collets, you can even take some off the collets BUT you need to be aware the bucket sits correctly pushing on stem and not on the spring cap, pushing on the cap can be a disaster...Depending on your seats you WILL need to take some off the collets after you take some off the stems to get within the height specs. LET ME KNOW if you need the measure, i meant to get it on here but forgot again....MRI will do that to you apparently !!!

A.E.

[Strika]

Thanks for the help all. I agree the seats appear to just be refaced than replaced.

I pulled the head back off again tonight, going to take it down to an engine builder mate see if he can help measure up a few things for me.

Few pics attached FYI.

I noticed that all the Exhaust valve stem protrude a noticeably past the retrainers whereas the Intake stems not much at all (All Exhaust valves are brand new)QUOTE

Cant see your pictures. BUT, here is a tip, MAKE SURE you get the correct tolerances to your mate to measure, I can dig thme up if you dont have a manual. YOu may not necessarily have needed new seats BUT if their old it is best. Now, the valve stem can be ground down until just above top of collets, you can even take some off the collets BUT you need to be aware the bucket sits correctly pushing on stem and not on the spring cap, pushing on the cap can be a disaster...Depending on your seats you WILL need to take some off the collets after you take some off the stems to get within the height specs. LET ME KNOW if you need the measure, i meant to get it on here but forgot again....MRI will do that to you apparently !!!

A.E.

A.E. you probably have forgotten more about machining heads than I will ever know, but to my mind, if you are having to shorten collets or valve stems, then really, the valves are seating too far into the head, which reduces compression for one. Unless you are of course recessing them for a reason, as in you have decked the barrells and increased the comp ratio and therefore need the valves to be recessed to stop them hitting the piston. Does that make sense???

[Angry Emmet]

[quote="Angry .

[/quote]

A.E. you probably have forgotten more about machining heads than I will ever know, but to my mind, if you are having to shorten collets or valve stems, then really, the valves are seating too far into the head, which reduces compression for one. Unless you are of course recessing them for a reason, as in you have decked the barrells and increased the comp ratio and therefore need the valves to be recessed to stop them hitting the piston. Does that make sense??? [/quote]

100% corrrect Mr Strika! It will, i reckon, be in a situation where new seats should be done, they werent much chop in quality back then, but new seats WILL HURT and he will then may need more valves, i'd prefer seats but its commone to take some off the collets and stems and these rockets dont do a lot of miles these days, spose depends on what he does with it versus how much $$$ left in the kitty. I know mine WILL get new seats next time, but hopefully that will be my 60th birthday present....in 2021...hint...hint...

[Sulli]

looking at the pic the head has not been skimmed as the residue of gasket element is still showing on the face of the head
provided the valves are standard they will extend above the retainers this is normal provided the matching collets are used
again looking at the pics I think that all he has done is lap the valves in opinions ??

[aggerz]

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.

I agree Sulli, head has not been skimmed upon second look.

Pic of the some of the left over bits from what I got for the $600 privilege.


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

[Gosling1]

Why weren't the inlet valves replaced with new ones ? The combination of re-facing the existing inlet valve seats, and re-using the old inlet valves, is why there is SFA clearance now.

[aggerz]

Right or wrong, there was one completely seized (stuck open) exhaust valve, the stem was bent/warped and it had to be belted out. I was informed that a couple of others were not in good shape either so that's why all exhaust valves and guides were were replaced.