Firstly, thanks to admin for welcoming me to this forum. I hope to contribute as well as learn from it.
I'm Ted. I'm a motorcycle technician with 20 years experience and eight years experience with a BMW main dealer. Although that was from 2012 onwards so as you can imagine, airheads were mostly unseen. I now work for a Kawasaki/ Suzuki dealer. I also run my own independent workshop at home for older bikes. Mainly from the 90's and 00's. I also work on BMW's from this era too. Although the R45/R65's are a new beast to me. But I'm learning quick.
Well, to the point. I bought an R45 from a customer who had a problem. He took it for a service at his local shop and after it came back the the engine would race away at high RPMS. Like a stuck throttle. He took it elsewhere where they rebuilt the carbs and it still did the same thing.
It came to me. I re-checked their work and they had re-build the throttles badly (choke parts mixed up etc). But after correctly rebuilding, that wasn't the issue. They also massively over-filled it with oil. Like 3x times the amount it should have (More on this later).
The old guy didn't want to spend a penny more on this bike so I bought it off him as project....
It has the old mechanical bean can. I suspected sticking bob weights so converted to an Electronic ignition. But still the revs still ran away.
Perplexed, I decided to pull the heads and barrels and measure up. Even though worn and a bit smokey, they wouldn't cause the run-away engine condition. However, there was a lot of burning and scoring on the pistons.
My theory is that the engine was so over-filled that the crank case breather was chugging oil into the carb manifolds and into the cylinder. Like It was running like a bloody diesel. This burning has ruined the pistons and cast iron cylinders. They're 40,000 miles old anyway.
The price of a re-bore and new pistons for the R45 is around £500. Nikasil cylinders from the later 1980 models aren't compatible with my 1979 due to a machined 'step' on the motor.
I could buy older cast iron R65 cylinders but they'd probably need a re-bore and new rings too. All expense.
I was considering spending £950 and buying the Siebenrock 860cc big bore kit. In for the penny, in for the pound
I was hoping folk on here would have experiences of the kit for the R45 ? Can she take it ? The con-rods run very smooth with no knocking.
I'd love to hear your views.