Rod bearing longevity

[professorfate]

I have an 83 R65 with 86,000 on it and was wondering how long the rod bearings last, and can you hear them when they start to go.  If you had the cylinder off and wigled the small end of the rod could you tell how worn?  Also I heard you need a special socket to get the rod nuts off?
Thanks

[Bob_Roller]

It seems to have been a bit of a problem with the '79 and '80 model year bikes, and I think we had a member here I think it was Wiemer, had a connecting rod failure about a month or two ago. I would think that by the time that it was noticeable by wiggling the the piston with the cylinder off, that there would be a knocking noise when running. Best I can remember about the connecting rod cap nut, is that it was a 12 point, some would consider this a specialty tool. But it is a commonly available tool from either Sears (Craftsman), or any other quality tool outlet. But being an aircraft mechanic some years ago, I'm sure you wouldn't consider it out of the ordinary.

[MrRiden]

Apart from having a 'rod knock' a very distinctive sound, or trying to wiggle the rod side to side the only general indication I can think of might be lower than normal oil pressure. Of course there are many other things that could cause this as you well know. If I had the cylinder off and felt any rocking play when manipulating the small end I'd remove the rod & mike the crank. I'm Just reassembling a Britt engine and got lucky using standard bearings on an in spec crank.
rich

[professorfate]

Someone told me this year not to use a plain socket on it or it will break,  I don't know.  I just read in the latest BMWMOA news that the airhead guru said something like 60,000-100,000 miles on airhead rod bearings but I thought the R65 might be more delicate as they don't hold up to higher compression pistons.

[Bob_Roller]

The torque on the connecting rod bolts is 35-38 ft/lb , so not exactly a high torque application. Now if someone is using a 1/4 inch drive, then I might believe it. I don't think that these engines are delicate at all, there are reports of 150,000 + miles without a problem, and then there are reports of catastrophic engine failure before 50,000 miles. I've got 80,000 miles on my '81 R65, and I'm not going to get concerned about, it until I get an indication that all is not well inside. I'm inclined to believe that previous owners not knowing what they are doing would be a more convincing cause than the bike itself.

[MrRiden]

I thought the R65 might be more delicate as they don't hold up to higher compression pistons.

Ditto to Bob and as for your concern, keep in mind the R45/65 are short stroke/higher rev motors than their big brothers = more revolutions per indicated distance. At least thats my thought.
rich
64k indicated before the odo died.

[professorfate]

OK thanks guys, I wont worry about it.  Next time I have the jugs off for whatever I will ook at the rods then.