RB261

[stokky]

Been asked a few questions about my 64ml crank and engine
I had a build blog on LCGB site, but seems to have been lost
So based on some saved pictures I had here is most of the build etc.
Details are :-
New Indian casings, heavily welded and strengthened for 64ml crank, and wider transfers etc.
Crank webs extra 5ml wider, believed to be same as Tino uses in his new 305cc Misano casing
Crank was sent off to be hardened
Fitted with a Vespa clutch bearing on main drive side (look closely and you can see an old vespa clutch bearing already fitted whilst some of the machining done. This held in via a groove and large circlip). Note all threads covered with bolts etc, to protect when blasted prior to powder coating
Mag side, uses 5ml packer to offset (so crank rod keeps same central position as normal). Some welding and grinding work to mag housing to match up with transfers.
RB250 barrel (extended my about 3ml, look closely on a couple of pic’s and can see weld marks)
Piston is a Wiseco 72ml, as per Kawasaki 750
72 x 64 = 261cc
Avanti Cylinder head, for better cooling, supplied as a blank and matched to kit.
Gearing is SX200 close ratio (cluster 4th gear dropped down from 21 tooth to 20)
Clutch is 8 plate, old school with crankcase packer, using normal springs (can pull in with my little finger)
Carb is Mikuni TM 38, with PowerJet
Exhaust is Adspeed Race 6, one off as had to be widened and lengthened to go round size of engine
Also uses MTech advance retard unit
All clever work done via Martin at Chiselspeed (Thanks Martin !!)

[Minority]

Wow!!!

Has it been dynoed?
Be interesting to know what sort of torque curve you got with those specs!

[molibdimum]

Ferkin show off

Seriously Martin its a thing of beauty.....well done.

[Knowledge]

Lovely work: both engine and chassis.

So the casing compensates for the crank's wider webs by replacing the standard drive-side bearing with a narrower bearing from P-range crank/clutch? Interesting.

A crank of those dimensions should be bullet-proof.

Have the engine been tuned for torque, or speed?

[stokky]

HI all,

yes all clever work done by Martin at Chiselspeed. (credit where credits due !!)
Although I did all build work.
Been on road all this year, without problems (other than vibrating at low revs, and loosening nuts etc)
Knowledge yes your correct thats exactly how crank fits in.
Have been sort of expecting to blow oil seal all year, but so far so good.
Not opened up too much, have been trying to run in properly, but you know how it goes with the temptation sometimes.
Popped a good few wheelies, and managed to spin back wheel when accelerating and was wet.


Also DC conversion, with battery hidden in void behind spare wheel. Includes both USB and cig lighter type connections for GPS or phone chargers etc

[tonydevon]

pure automotive porn

[stokky]

[stokky]

don't comment on kickstart, that was a bodge job whilst I got one welded up to fit snug and chromed

[bolzenanker]

As said, a thing of beauty. Very nice. Got a rear bumper thing going on there I see?

[Knowledge]

That looks like an AF lightweight flywheel. I would have expected a a heavier flywheel.

Are you able to get away with this because there is more mass in the webs of the crank?