Valve clearances

[Zomerset Zed]

Well only done 72 miles of running in and on my last ride noticed the top end was a bit noisier than previous ride. So off with the cam cover and have a look.

Measured all the valve clearances (stone cold engine) and below is what i measured:

1st no. in brackets is clearance as initially built, second number is today's measurement.

Inlet 1 to 4:
(4)2
(6)3
(6)6
(5)5
Exhaust 1 to 4:
(7)5
(11)12
(8)13
(9)5

All measured in thou's

I guess its no 2 and 3 ex that are making the clatter.
Valves, guides, and all valve gear is Unitrac standard kawasaki, including shim under bucket and Unitrac cams.
So what's anyone's opinion on how to proceed?

Options as i see it are:

Keep on riding it and see if it improves (sticking valves)
Take the head off to assess

Also had a wee bit of smoke on start up after a couple of days without running time before last. But no smoke on last start up.

[Pigford]

Rob will be along in a bit - but until then, target gaps at top end 0.10 - 0.15mm.

Hopefully they're just settling in a bit

I have the correct shim tool & a wide selection of shims if that helps

[ADRIAN H]

Not sure what the numbers you’ve given refer to. Correct clearance is 0.10 - 0.15 as Pigford said. Always aim for the larger gap.

[Zomerset Zed]

Not sure what the numbers you’ve given refer to. Correct clearance is 0.10 - 0.15 as Pigford said. Always aim for the larger gap.

All measured in thou's

Yes, i know what they should be. I am asking what people think may be the reason for some of them opening up a wee bit.

I have the correct shim tool & a wide selection of shims if that helps

Thanks Piggy, but they are 13mm shims under buckets. At least i know what size shims are in so i can just re-shim to get correct clearances back, but would like to understand whats going on first.

[z1bman]

yes no 2&3 are double the maximum clearance required

[Zomerset Zed]

yes no 2&3 are double the maximum clearance required

Yes thanks i know they are, actually over x2

[Julian_Boolean]

Unusual for clearances to open up, possible causes

1. You didn't measure them properly
2. The valve isn't fully closing
3. You've had sudden wear on the part of the camshaft that shouldn't touch anything
4. The cams aren't in properly
5. Your buckets have suddenly worn
6. Your shims have suddenly worn
7. You've bent two valves

[Zomerset Zed]

All possibilities Julian, other thoughts were maybe valve seats are dropping out of the head?

I missed a gear on one of my rides but tell tale tacho tells me 8,600 rpm which shouldn't be a problem as i have loads of piston to valve and valve to valve clearance.

Next is to get the endoscope out and see if i can see anything in the combustion chamber. Doubtful, but worth a try.....

[z1bman]

have you checked the compression ?

[Zomerset Zed]

Some crap pictures off the endoscope showing nothing particularly useful. Also did some video, but cant get them off my phone for some reason.

When you look at the camera live you can clearly see that there are no witness marks on the top of the pistons where valves may have contacted pistons. So that's good news at least

Inlet valve:

20180427173521.jpg (62.28 KiB) Viewed 4060 times

Exhaust valve:

20180427173555.jpg (58.15 KiB) Viewed 4060 times

Exhaust valve pocket on top of piston:

20180427173756.jpg (58.4 KiB) Viewed 4060 times

[Zomerset Zed]

have you checked the compression ?

Not yet as i can't find my gauge. Now did i lend it to someone?????

[zed1015]

Rob will be along in a bit - but until then, target gaps at top end 0.10 - 0.15mm.

Sorry for the delay . Been to Mallorca for a week.

All gaps should be up around 0.15mm when first assembled .
0.16mm to 0.17mm is better than 0.11mm as a fresh valve and head build usually settles and the gaps may close slightly after a few miles..
Even 0.20mm is ok with race cams but those initial 8,9 and 11 numbers are too wide for any cams..

Main common causes for inconsistent or widened clearances are.
1 - Bent/ Sticking valves.
2 - Valve stem tip ground out of true.
3 - Dished buckets/shims ( depending on follower type).
4 - Fractured shim.
5 - Excessive cam wear ( unlikely after only 72 miles unless you have a severe lubrication issue )
6 - Flawed measurment method.
7 - Debris/grit on upper valve train when taking initial readings which has now been crushed or washed away during running.

6, 7, 2 and 1, in that order are the likely culprits.

I would..
1 - Take feeler gauge readings fully on the base circle with the cam lobe facing 180 degrees from the shim
2 - Re-shim to correct 0.15mm spec.
3 - Check compression and Leakdown..
4 - Spin motor with plugs out and re check gaps.
5 - If all ok go run the bike a good few miles .
6 - Re-check and if ok leave it and if not ok it's head off time.

Also check that the cam caps are not loose.

[Zomerset Zed]

Cheers Rob, as always you are a beacon of sensibility and Zed knowledge. Agree with everything you say btw.

Uncannily i am currently in Mallorca riding bikes!

After having a chat with Dippo, who built up the head we have come up with a plan. We think that it is just the shells bedding in. Remember the cam cap/shells/cam binding saga??

So when i get back i will first do a compression leak down test to see if we have possibility of valves getting hung up. I will order shims to correct clearances , then run for a bit and see what happens.

Have already checked the caps and they are solid. Don't think there is any lubrication issues as all very wet in there, so that's good news.

Will do all the other things you have also suggested and i will inspect ALL the shims. Interesting point about the valve stem grinding out of true. Hadn't thought of that one as Graham did grind some of the valves to get sensible shim sizes in.

Thanks for your input and will let you know how i get on....

[zed1015]

Uncannily i am currently in Mallorca riding bikes!

Yes! a bit of a coincidence.
Could have met up for a beer if I had known.
A bloke wearing a Z1 owners club t shirt would have been easy to spot.