hi,
I am rebuilding the heads on my R80/7 1980. i would like to change the valve seats so i can use unleaded. on the parts sites i can only find exhaust seat.
For models listed with 38mm exhaust valves ( Suitable for unleaded fuel )
I would...and did on my R100/7. I changed seats as well as the valves. Who is doing to work for you? If some shop, can they get the parts you want? And are they familiar with the details of Airhead valves? I don't know specifically what that is, but I've heard it from many people that all heads and valve jobs are not the same.
Kurt in S.A. wrote: ↑Thu Oct 03, 2024 11:00 pm
Sadly I don't think Ted does Airhead heads anymore. He might have sources for parts though.
Kurt
The Beemershop no longer does that type of work anymore. They concentrate on suspension aka shocks and other parts. It’s a bummer as they were a great independent shop.
Jeff in W.C.
1988 R100 RT
2018 R1200 GS
"I've got my motorcycle jacket, but I'm walking all the time." Joe Strummer/Clash
Kurt in S.A. wrote: ↑Thu Oct 03, 2024 3:13 pm
I would...and did on my R100/7. I changed seats as well as the valves. Who is doing to work for you? If some shop, can they get the parts you want? And are they familiar with the details of Airhead valves? I don't know specifically what that is, but I've heard it from many people that all heads and valve jobs are not the same.
Kurt
i am getting a local ish (UK) engineering company same guys do re bores, crank re grounds amongst other things. i will ask when i drop thr jugs off.
billy
It is not normally necessary to replace inlet valve seats unless there is some obvious issue. They aren't affected by the 'unleaded' problem which affects exhaust seats.
I would echo the comments above that it is important to find someone who knows the airhead engine and who has suitable tooling. My nephew who ran an engine rebuilders wouldn't work on my airhead heads because they didn't have a suitable tool although his shop did other work on the engines for various well known british BMW airhead specialists.
billy192 wrote: ↑Thu Oct 03, 2024 3:07 pm
hi,
I am rebuilding the heads on my R80/7 1980. i would like to change the valve seats so i can use unleaded. on the parts sites i can only find exhaust seat.
For models listed with 38mm exhaust valves ( Suitable for unleaded fuel )
do i need to do the inlet seat also?
Thanks
Billy
The mechanism that causes valve seat recession would suggest that the inlet seat doesn't need to be changed. Lead in petrol acted as a sort of lubricant to the valve seat. In it's absence micro welding can take place between the valve face and the seat which slowly removes material causing the valve to recede into the seat and the clearances to close up. This is a temperature related effect so the cooler running inlet seat is not affected to the same extent if at all. Also because it's temperature related, a smaller capacity cooler running airhead that's not used at sustained high revs might not suffer recession at all even if the original cast iron seats are retained. Anything ridden hard is much more likely to suffer particularly if they have BMW's first attempt at unleaded seats from 81 which because of poor thermal conductivity, turned out to be worse than the older cast iron ones.
