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Discussion in 'Airheads' started by lloydunknown, Mar 20, 2011.
Are you done?
I understand that the guides and seats are an interference fit. Would it be possible to heat the heads to remove the seats and guides? Then, could I freeze the guides and head the areas in order to install the new parts?
I can't afford the big bucks to send this out to a shop. I was hoping I could get away with not having to machine the heads.
Has anyone ever done it this way?
You're not going to be able to change your seats at home in your garage, but the guides are doable if you're handy, reasonably experienced, properly equipped and careful.
I don't know you, but it's probably not the sort of thing you want to try alone without a bit of guidance and the correct tooling. You could do a lot of damage if you weren't careful.
If money's tight, take the heads to a competent auto engine overhauling shop with CC Products guides and new exhaust valves in hand and specify 1.5mm valve seating surfaces. (iirc?)
Better double check that spec.
edit: or wait until you can afford to send them to a motorcycle head specialist like Randy Long.
If you have an electric welder ( stick, MIG or TIG), you might be able to do it at home although I would not recommend it unless you are sure you are up to it. Chances are the seat bosses are too out of round and need to be machined anyway. Be sure and have the base of the bosses straightened as well as the sides. Then be sure your seats are taller or they won't be proud enough. Typically, proud seats flow better and, of course, get you more compression. You can very often see where exhaust has been getting under the seat. You have to have the right setup to get them back in plus all the measuring tools. It not for the faint of heart!
But all of this is conjecture. Valve lash doesn't normally go away that quickly.
Give it some time to get more data. And, who knows - you just might stumble across some low-mile or recently rebuilt heads for a song. These bikes are actually pretty rugged and have travelled loooong distances with worse troubles.
Don't worry yourself into a dither before you really know if something needs attention. Ok?
Also, I wouldn't consider doing my own heads even though I do most everything else. It's one of those things bordering on art and can trash an engine all too quickly if not done right. Especially the seats! Don't even consider them!
get valves and guides as a kit from motobins and save yourself some cash. After market valves (swiss intervalves). A good engine machine shop can do the seats.
I agree. I too would have real serious reservations about your servicing your heads unless you're familiar with doing that kind of work on Airheads and are in possession of the right tools. Airheads engines aren't that complex but the work does need to be done correctly. (In the German sense of the word!)
As far as having them done at a non-BMW specific shop, you might inquire at whatever shop builds race car heads in your neighborhood. In my town, the local hot rod head shop does heads for all of the MC shops, including those specializing in Beemers. The work is first rate and there are real savings in using them.
More data? Absolutely! But beyond that, I'd do a visual inspection of those exhaust valves and I'd continue to look at em on a regular basis. Remember, I said look! The last couple of millimeters of valve frequently disappears very quickly (JAMHIK!) and if you drop a valve, the costs of repairs are going to skyrocket.
Also +1 on finding a set of good used heads. Keep your eyes open and good luck!
Heres a severely recessed exhaust valve:
Click for full size!
Heres the valve that might have lasted another 1K miles: