WDCO unleaded petrol

[PapyG13]

Hello everyone, here is how to modify your cylinder heads to go unleaded, there will no longer be any need to put any additives in your petrol.

It is necessary to measure the internal diameter of the original seat, then put the valve and measure the protrusion of the valve stem in order to put it back at the same height (or if the seats have already been rectified too many times, it will be necessary to reduce the valve stem protrusion).

you can now machine the seat housings. 
Either you go see a specialist, or you have to make an assembly to do it on a milling machine, and make a pilot that fits perfectly into your guide to perfectly align you. For tightening, you need 0.06/0.07mm of tightening (0.00236 to 0.00275 in).

to insert the seat, you can do it without heat the cylinder head If you have access to liquid nitrogen, otherwise heat the cylinder head to 200° to facilitate installation. Once the cylinder head has cooled, remember to tap on your seat to ensure that it is fully seated.

It now remains to rectify the seat blanks to the correct height. For my part I make a modern valve supports with 3 angles. width of my valve supports 1.2mm (0.047 in).

I'll put you before/during/after photos.

If you have any questions, don't hesitate!

Edited October 25 by PapyG13

[Ron]

Nice work and series of pictures. However I've never found unleaded petrol to be the problem it was threatened to be. Ethanol is more the worry these days. Ron  

[PapyG13]

Hello Ron,

The lead was also used to "cushion" the valve on the seat. I have seen several times people ride without additive and the seats were damaged / the valves were hollowed, or both.
Depending on the cast iron the results are different.