Cam gap - what's happening ?

[ADRIAN H]

personally i would change the bolts in the cam caps & start again


https://www.matthewsvolvosite.com/stret ... bolts.html

+1 replace the cam cap bolts. As the threads on these do stretch quite easily.

[1975-S1C]

Ok, that sounds like the way to go to start with anyways. I'll get some ordered up and see if that sorts it.

Ref my last post, is it ok to leave the exhaust cam alone as that's all in good shape and I'd rather leave it alone if possible, or can I just remove the inlet cam and upper idler ?

[z1bman]

yes you can leave the exhaust cam as it is

[z1bman]

it could also be down to weak threads in the cylinder head as its a very common problem

[1975-S1C]

Thanks amigo. I'll give that a go and report back. At least if nothing else it'll rule that out.
Appreciate all the help as always.
Paul

[warren3200gt]

You sure the cam shells are clean and seated correctly?

[zed1015]

Is it ok to leave the exhaust cam bolted in place and just remove the top idler and inlet cam ? Or must I remove both cams ?
Cheers

Answer to that is YES! just don't rotate the crank afterwards.

If the clearance keeps changing you either have a sticking valve / sticking bucket / debris on the valve or seat or possibly a bent valve or out of true valve stem tip if they have recently been ground to increase shim sizes .
If the cap is bolted down tight I would rule out any chance of the cap shifting under hand rotation and it appears you have eliminated the cam bucket for stiction and if you have had the valves out and they refitted with no difficulty then that would suggest that they also travel freely in their guides.
You have to rule out the valve seating first so you need to flush the valve seat with some petrol and simultaneously spin the motor on the starter with the plugs out to clear the seat and settle the valve.
Do this 2 or 3 times with a wide clearance to be sure the valve hits the seat and then go back to setting the clearance.
Hopefully that should do the trick and you will get a consistent reading.
If not you will need to do a leakdown test to confirm the valve is seating and go from there.
No point in complicating this reply with more possibilities until the above test has yielded it's result.

[1975-S1C]

Ok I can give that a go also.

Just took the inlet cam and top idler off. All seems well with the shells being clean and well seated. The cap did seem to be down tightly I'd have to say, and No visible signs that the bolts are stretched / waisted, but I may as well replace them anyways just to be certain.

The bucket moves easily with my finger and the valves moved freely in the guides when I assembled it.
I suppose it's possible that some crud has gotten onto the valve seat, though I was careful to make sure it was all clean when I assembled it. Will flush through and see if that helps anyways.

I'd be surprised if the tip grinding was out of square and they only took about a quarter of the amount off that this is jumping around by.

The strange thing is, it was just under tolerance until I put the shim tool in to hold the bucket down and switch shims. The gap did seem to get bigger each time I subsequently switched to a larger shim in an attempt to close it.

Anyways, some things to try now to see if I can narrow the problem down.
Cheers

[Steve Cooke]

Where the valves checked for trueness? any sort of bend can make the valve bind up.

[1975-S1C]

Zed1015 was correct.

I decided to just take the head back off again and rule out anything to do with the valve.
Poured petrol over the top of all of the valves and hey presto the one where I was having problems pissed out fuel, whereas the other 7 didn't leak a drop.

Took out the valve expecting to find a piece of crud or maybe have to re-lap it, but what I found was a valve that is bent I'm guessing I must have done this somehow when I tried to swap the shims over, so I'll put my hand up for being a muppet. Not sure how though as I didn't feel or hear anything when I was turning it over slowly and carefully with a spanner on the crank.

Anyways, what's done is done I guess. I'll have to get a replacement valve and get it ground down to the length I had the other ground to so that I get back to a healthy shim size.

Thank you all chaps for your help with this, I do appreciate it.

I shall now go and stand in the naughty corner (after I've ordered a new valve of course)
Cheers
Paul

[z1bman]

camshafts should be in this position when the valve timing is set correctly noting the position of the notches in the end of the camshafts

[1975-S1C]

Yes indeed, it was exactly like that.
I think the fault is all mine and I'm sure I know what I did wrong, and it was a misunderstanding of how to use the shim tool correctly. I think the exhaust valve and inlet valve must've come in contact and that's how the inlet valve bent. I've checked the exhaust valve and it's fine, so just need to replace the inlet valve and move on.
I feel like such a plonker and am frustrated with myself, but at least I know what went wrong and how to put it right.

I will get a new valve ordered tomorrow, get it lapped and then calculate the adjustment I need in length and get it re-ground to the correct length and hopefully all will be well.

It's so frustrating as I could have had it finished if I'd known what I was doing, now I feel like a bloody idiot and have set myself back a week or so.

Anyways, much as I am a plonker, at least I know what the problem is now and how to sort it.
Should be back to where I was before in a week or so.

Cheers

[Pigford]

Yes indeed, it was exactly like that.
I think the fault is all mine and I'm sure I know what I did wrong, and it was a misunderstanding of how to use the shim tool correctly. I think the exhaust valve and inlet valve must've come in contact and that's how the inlet valve bent. I've checked the exhaust valve and it's fine, so just need to replace the inlet valve and move on.
I feel like such a plonker and am frustrated with myself, but at least I know what went wrong and how to put it right.

I will get a new valve ordered tomorrow, get it lapped and then calculate the adjustment I need in length and get it re-ground to the correct length and hopefully all will be well.

It's so frustrating as I could have had it finished if I'd known what I was doing, now I feel like a bloody idiot and have set myself back a week or so.

Anyways, much as I am a plonker, at least I know what the problem is now and how to sort it.
Should be back to where I was before in a week or so.

Cheers

Don't sweat it - I've bent 2 x sets of valves over the last +30yrs due to not thinking properly .... last time it was whilst adjusting the cam chain, about 15yrs ago

[1975-S1C]

Thanks Pigford. It's so bloody annoying though !

Where's the best place to be buying a replacement valve chaps ? And are there any makes to avoid / prefer ?

Cheers

[zed1015]

You either want a new stock valve from say Cradley Kawasaki of maybe Debbens or one of these from Nick at Suzuki performance.
http://www.ebay.co.uk/itm/Kawasaki-Z900 ... 3641.l6368

Beware those cheap valve sets that work out at around a tenner per valve as they are shit quality.
I have dealt with a few of those and they are very inconsistent, mostly being too long with the keeper groove too high up which makes it almost impossible to get the correct valve height without some serious machining.

Also make sure you get the correct keeper groove type as your other valves.
Square on the early valves and round on the later.
Either type can be used though as long as you use the matching collets.