BMW Crankshaft

[Jay]

We've been hearing a lot about what a monster the new BMW is. I was especially interested in the crankshaft as I was told it was considerably lighter than a GSXR1000.

Well Friday we got our hands on one. The rumors were true 16.3 lbs. This has got to aid in the ferocious acceleration. BMW is on to something.

The counterweight design is like a Honda 600 where there is not a lot of area the factory can drill holes for balance. This crank was 2 grams out on each end. Both on the same side, and heavy where they couldn't drill.

When this crank left APE it was virtually dead nuts on ( which doesn't always happen ). less that 1/10th gram end for end.

GSXR and ZX10 guys, we can make your cranks close to what this BMW is.

APE Racing Crankshafts and Crankshaft Services

[WANTSUMSAKI]

THANKS FOR THE RESEARCH AND THE HEADS UP!!!!!

ALEX HUGHES

[redline65]

Doesnt look like it would be friendly to big hp

[xclr82xtc]

in my experiance, a light crank might be good in road racing, but ive found that the extra mass help gets the bike up to speed without bogging the motor on launch (think flywheel) ...just my two cents, both ways work.

[Jay]

I think the BMW shows that if you have enough power, you don't need to store that much kinetic energy.

[xclr82xtc]

in the same sense, most lightened crank shaft 1000s are built motor high hp bikes..so...same deal lol. ill be sending a crank soon...can you de-stroke?

[Jay]

Yes we do.

[DOLLAR]

why destroke.

[not7fifteen]

"longer" pistons or revving to the sky?

[pafundi]

To dollar. Shorter stroke to turn it harder RELIABLY. Long stroke motors can be turned hard but they wont last. So shorten the stroke and turn it real hard reliably when chasing big hp (hp a factor of torque and rpm so design motor to make good torque at real high rpm for big power) shorter stroke will allow you to do this with longevity as creates much less stress on the pistons, rods, bearings, crank, cases ect.

[xclr82xtc]

why destroke.

you'll find out soon enough

[xclr82xtc]

To dollar. Shorter stroke to turn it harder RELIABLY. Long stroke motors can be turned hard but they wont last. So shorten the stroke and turn it real hard reliably when chasing big hp (hp a factor of torque and rpm so design motor to make good torque at real high rpm for big power) shorter stroke will allow you to do this with longevity as creates much less stress on the pistons, rods, bearings, crank, cases ect.

a engine is an air pump. there is 3 ways to get air into a motor. forced, chemical, and the third one relates to destroking...but there is more to it than that. lets just say i found the valve spring limit.

[Jay]

We actually do quite a few destrokes for the 600 mini spring guys, and others that race in a cc limit.

The idea is, by starting with an oversize motor, and destroking it to get to the limit, you wind up with a bigger head with larger valves, then if you took a smaller motor, made it larger, then tried to bring the head up to handle it.

[Jay]

Just finished a GSXR1000 with the counterbalancer gear removed. 16.4 lbs. Now this one gives up nothing to the BMW.

[HMI Racing]

Just finished a GSXR1000 with the counterbalancer gear removed. 16.4 lbs. Now this one gives up nothing to the BMW.