R50/5 motor to R75/5

[briana]

I have a 1971 R50/5 that is in rough shape at best. I got it cheap and was looking for a project. It will probably end up as a cafe racer style bike. The complete top end has to be rebuilt / replaced, and i figured rather then rebuild the 50 maybe i could bolt on 75 cylinders and heads. Is this possible and what else is involved, carbs obviously, but what about connecting rods and that stuff. I'm asking not only because it would be a little bit of a power increase, but it would also give me more options when looking for motor parts. Maybe this isn't even possible, but i thought i'd ask here.

Brian

[20774]

A quick check shows that the stroke is the same for the two /5s. However, I wonder about the camshaft...the part numbers are different. One lists it as a "284" cam while the other is a "336" cam. I'm not sure what that means in terms of performance. The pushrods and lifter part numbers are the same.

[mymindsok]

The conversion that youre talking about is possible but it would cost a lot less to simple swap in a good running 750 engine.

Think about this...

By the time you buy some 750 jugs and pistons, a 308 cam and all of the gaskets, seals and small parts to make the conversion, I gurantee that you'll spend more than $1000. OTOH, the 14K mile 1981 R-100RT engine sitting in my garage and ready to install is worth..... $1000 cash on the used parts market.

If your bike is rough, save your money, time and nerves. Buy a bigger, nicer bike and then start changing things.

PS: the 336 cam is the BMW "performance cam" and has nothing to do with conversions. If you need more top end performance, install the 336 but in an early or hi-comp engine you'd better know what youre doing!

[20774]

PS: the 336 cam is the BMW "performance cam" and has nothing to do with conversions. If you need more top end performance, install the 336 but in an early or hi-comp engine you'd better know what youre doing!

Yup...I see that now that I scroll down a bit more on my ETK listing!! Should have been 308.

[37071]

My friend Terry got some R90 jugs, pistons and heads cheap. He bolted them onto his R60/5 motor 10 years ago. He replaced the Bings with Mikunis and put on a SS 2 into 1 exhaust. This bike pulls a wicked wheely. It spends no time above 80 mph. He has had way too much fun with this bike.:nod

[briana]

Gar do you have his e-mail address, i'd be interested in finding out what else he had to do.

Thanks,

Brian