Howdy folks!
Happy to be a new owner of a 1978 R100RS. Also happy to be a new member of this wonderful community.
On to the problem at hand. I ripped my heads off to be rebuilt/converted to unleaded-safe by the master Ted Porter. Upon gaining access to the cylinders, I noticed one side looks to be in pretty bad condition. As this is the first time I’ve seen this sort of damage, I was hoping to tap the wisdom of you folks that have collectively seen hundreds of these things. So please, how concerned should I be? Should I trash this cylinder and use this as an opportunity to get some nikasil cylinders?
Oddly, I’ve got different size cylinders. The left (damaged) one is stamp A 1S. The right is stamped B 2S.
Thanks!
Welcome aboard !
• The important question is "how was the bike running?" If you had been riding the bike with minimal oil burn and good performance, then there's nothing wrong with the cylinders. It's not how they look to you, it's how they perform with the rest of the engine.
The cylinders need to come off anyway, to replace the base gasket and lower push rod tube seals. I'd have a (hopefully non-BMW) shop hone the cylinders with a "glaze breaker" not to remove metal, but so you can install new rings. After the cylinder is honed is the first time anyone will be able to discern pits in the glazing from pits in the cylinder wall.
• Same with the heads. Ted Porter's work is really outstanding, but the fact that the bike has been running on unleaded fuels for 2 decades sort of begs the question "Why now ?" It would certainly be nice if you plan on adding another 150,000 miles before you retire the bike, and it will certainly end valve adjustments every 3000 miles. But again, if the engine was performing well, the accepted mantra is "if it ain't broke..."
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Thank you for the reply Wobbly. The bike is brand new to me, so no real baseline for oil burn. Great advice having the glaze-breaker hone done on the cylinders.
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