Valve replacement.

[Deleted account 111026]

I've bought a 1977 R100RS which is to be the basis of a cafe-racer project.
I intend converting the heads to run on unleaded which will mean changing the exhaust valve seat, at the same time I'll replace the exhaust valve.
I'm sure I've read that the earlier airheads had problems with the valves losing their heads, does this apply to both the valves or just the exhaust?
If there is the chance of a problem, I would rather change both valves whiile the heads are off. The bike has covered about 90K kms.
Thanks in advance.

 

[(RIP) pastyman]

at that mileage, yours is ripe for the valves breaking. I believe its caused by worn guides allowing the valves to "twist" if thats the richt phrase, then as the heads are friction welded to the stems they break off. I think it is mainly the exhaust but I think the inlet can also let go.
I would be inclined to renew the guides then fit new valves etc
Im sure someone will be along to give you the proper advice though

 

[(RIP) Proff]

No need to Pastyman, you've told him exactly what I would have done

Before replacing valve seats tho' check they ain't already been done. you can see if an insert has been put in
Also regarding valve guides. take spring off and check for play by moving valve up and down guide whilst checking for play

 

[Wanderer]

MotoGS1100 - any pictures you could take whilst undertaking this job would be much appreciated

 

[Deleted account 111026]

Thanks for the advice, guides will be checked and 4 new valves fitted.
The cafe racer project will start next month, I would like it finished before May as it will be an ideal bike to use as the classic bike weekend at Dijon, 2009.