Won't start

[Mang]

Excellent and clear instructions Evil.

I am still confused as to what I do with the shim sizes as I believe the inlet valves are permanently compressed making the maths difficult as I can't get an existing clearance figure.

Your help to overcome my stupidity is much appreciated.


Mang

[Evilchicken0]

OK - take your measured tollerance as 0 and your desired tollerance (0.11 to 0.20mm) as the widest value 0.20mm

[ Measured Tollerance + Existing Shim Depth ] = [ Desired Tollerance + New Shim Depth ]

[0 = Existing Shim Depth] = [ 0.2 + New Shim Depth ]

Existing Shim Depth- 0.2 = New Shim Depth

It's not ideal but when you get into the whole thing you'll need to round up and round down a little anyway. It's a bit suspect that the all the inlets are at 0, the engine would have stopped running before this so you'd expect 1 or 2 to be measureable. have you tried measuring with the cam lobes at 12 O'clock ... it takes longer but it can easier to wiggle the feeler gauge in there. Maybe somebody tired to this before and got their maths wrong then lost heart.

[hunter]

If you have any tight valves, Remove the shim fit something thinner,
Then calculate.

[Mang]

Evil
Thanks for explanation. Your methodology and logic was what I had guessed at but good to have confirmation.
5 of the inlet valves have no clearance.

Hunter
Thanks for your input and I think that I will try your suggestion.

[Evilchicken0]

5 of the inlet valves have no clearance.

I guess we know why it fire up then

[Mang]

Hope to get onto it this evening. As I have not dismantled yet but found a bucket full of shims can anyone tell me what diameter the shims are and I will see what sort of selection I have.

[hunter]

I think they are around 7mm.
7.48mm.

[Mang]

Decided whilst I had the bike in bits to take head off to inspect the valves as something may be wrong as the inlet clearances were very low. So on inspection nothing really wrong with the inlet valves and seats but the exhaust valves and seat are very poor so I think I need the seats recutting and replacement exhaust valves

How much does seat cutting cost. Can you do it yourself? Is it easy to get second hand valves that are in good condition?

Also is it advisable to replace the base gasket, do they leak if the head has been removed?

Again thanks in advance of your help.

[Evilchicken0]

New seats really need to be machined - youre better off getting a seconhand head or just close your eyes a bit
Clean up the carbon, clean up the valves and piston crowns, nail it back together and ride it.

Yes you should replace the head and base gaskets. Best practice would be replace the gudeon pins for the small end bearings and the valve stem seals

[Mang]

Well a good inspection of the the valves and valve seats has lead me to the conclusion that a replacement head is the way forward.

Someone, at some time in the bikes history, has modified the the valves on a lathe. I have no idea what they hoped to achieve but they ruined all the inlet (not exhaust valves as I said) valves by badly (and I mean badly) turning their own profile on the valves which means there is no sealing surface between valves and head! The "land" that should be ground in to get a good seal is smaller in diameter than the valve seat diameter. Not content with this appalling modification some work was undertaken on on the inlet seats replicating the surface finish on the valves, a shocking seat recutting job. No chance of the surfaces mating.

Why did the compression show good when checked - totally in accurate compression gauge?

I am now looking for a new cylinder head!!!

Mang