Hello, new to the forums though I've been reading extensively.
The Deal: '75 R60/6 seen here
Looked at it yesterday and took a short trip down the road with it. The owner has only had it for a year and never registered or licensed it. (he has a couple other licensed bikes). He said he didnt really like the bike because of weight (compared to his honda 450F im guessing) and how expensive the parts are. He seemed to be honest and not really in a hurry to sell the bike. He actually vouched for the Honda CBs after i told him i was also looking at a '74 CB550F.
Issues that I could see: The seat is missing the rear hinge, Right carb leaks gas, Right cylinder pings while idling, the threads on the right carb where the choke attaches are busted off (choke still works). The odometer/spedo has been replaced at some point. It reads 22K but the title says 58k. The headlight switch is loose, doesnt 'click' into place. The clutch seems to grab late. (adjustment?) The transmission felt smooth and it didn't come out of gear at low rpms. The shift lever has about an inch of play at the end in neutral (normal?). Small ding in the tank. The emblem is all brown. The guy coated the tank because he said it was rusty when he got it. There is a small dent / crack in the front left side of the motor (!!!).
So the bike obviously needs some work and cosmetically it isn't perfect. I thought $2000 was a decent asking price. The carbs and valves probably need adjusting. I figure I should at least give an offer, like $1500. What do you guys think?
Definitely start low...I think $2000 is the top end given all that is wrong. You can buy other good running bikes in better shape for $2000.
As for the pinging, the R60/5 and 6 models were pingers from the beginning due to high compression ratio and aggressive cam profile. This was usually fixed with compression reducing base gaskets (takes the guts out of the motor, though) and the Boyer electronic ignition which has a delay in the advance curve. Pinging at idle is troublesome, indicating that there might be extensive carbon build up causing even higher compression. Did it ping when riding or accelerating? Maybe it's just loose valves or rocker arms.
The lever play is at the handlebar? That could definitely could result in late engagement. Also, you'll need to lube the transmission input splines. This is something you should do on any new-to-you Airhead just so you know the state of the splines. The clutch will shift better as a result.
The tank emblem has just yellowed...they do that, but it does show the "patina" of the bike.
Pinging and it's cousin, detonation, are definitely bad for the engine. What's happening is that the gas is combusting or exploding in advance of the proper firing point. Basically, the piston is still moving towards TDC (top dead center) and the gas is not burning and expanding, thus pushing against the piston. Normally, this happens just as the piston is clearing TDC and on its way to BDC (bottom dead center). Pinging will slowly wear away at the piston top and combustion chamber...eventually, you'll hole a piston and bad stuff will then get into the oil and bearings, etc. Detonation is a stronger version of pinging and can hole a piston or create enough forces to damage the wrist pin, bend a rod, or create forces that damage the main bearings.
Bottom line, you don't want pinging if you can help it. As I said, the trick on the R60/5 or /6 is to find a way to retard the ignition. The Boyer electronic ignition is a good choice. It has built in advance curves which are more gentle for the R60.
Yes parts are expensive, but the prices fluctuate depending on what's happening overseas. There are vendors who sell quality aftermarket products. There are relays, bulbs, etc., that can be substituted which are much cheaper. I use cheaper stuff once in a while, but for critical things like oil, cables, engine parts, clutch parts, etc., I'm going to use BMW. You can run battery from Walmart if you want to. You can use any old oil you want to. There might be reasons not to do that, but sometimes saving a buck here or there is going to bite you later.
If you haven't heard it before...sometimes "the cheapest thing on a BMW motorcycle is the rider".