Short stroke crankshaft for 998
Turbo Mini Forums

Hi

I was wondering what crankshaft would be suitable for a 998 short stroke screamer. Was thinking about the 850 cranks but arn't they a bit weak?

Any body any ideas?

Thanks

Tom

According to Vizard the 850 crank is supposedly good for 9000rpm with the proper treatment.

The problem is that they need custom thrust bearings to be fitted to a 998 block.

I'm using one in my K100 build. 998 block bored +0.120" and 850 crank gives an all square 980cc.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thats exactly what i am planning to do. Currently got the K100 head and was thinking either +.080" or +.120".

In what way is the crank different in that it require custom thrust bearings?

Thanks for the reply. Just the kind of response i was after.

Tom

The centre journal on the 850 crank is wider, so you need thicker thrust bearings.

I've bought a piece of hollow phosphor bronze bar to make some thrusts.

At 0.080" you will have to relieve the block for some of the valves, as Miniboo has found out. But at 0.120" it should just clear with the standard bore centres.

Bit more here:

Edited by Paul S on 13th Jun, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yeah i have just dropped my block off for some more "mods" to allow the valves on 2 and 4 to clear. i reckon +120 will clear but only just.

Osselli can make you custom thrusts if needed. Just tell them the thickness you require

Paul

I seriously doubt it!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i am thinking about getting my machine shop to make a spacer that bolts on and then screw the normal thrusts to that. does that make sense? i am sure i saw a post on here, where someone had screwed the thrusts onto the main face.

Edited by miniboo on 15th Jun, 2008.