6 replies to this topic

[Dr Simon Peach]

What is the minimum size the big end can be before the crank is useless. I think mine has been ground down past its best. I'm not sure +30 shells will be any good. That's the max I can find.

Cheers
Simon

[Tupers]

To start off you need to find out what you have at the moment so either measure your main journals or look at your shell bearings, the size should be etched into the back.


Mini Spares supply 998 shells up to +.060” or 1275 shells up to +.040”. For a fairly standard road engine you’ll be fine it’s only the higher performance end of the spectrum where might want to be careful about thinning down the crank.

Edited by Tupers, 11 September 2022 - 09:45 PM.

[DeadSquare]

To start off you need to find out what you have at the moment so either measure your main journals or look at your shell bearings, the size should be etched into the back.


Mini Spares supply 998 shells up to +.0060” or 1275 shells up to +.0040”. For a fairly standard road engine you’ll be fine it’s only the higher performance end of the spectrum where might want to be careful about thinning down the crank.

My Mimispares catalogue only shows up to +.030".  How recent is your information ?

[Spider]

Even for 1275's, you can get shells down to -0.060", though you may need to go looking. I know Matt Read usually has them.

 

You won't reduce the life of any crank by making the journals smaller, it's how much fatigue it's had that will 'set' it's fife.

 

Grid away without any fear.

[Tupers]

My Mimispares catalogue only shows up to +.030". How recent is your information ?

+.060” big ends for 998 http://www.minispare...|Back to search

+.040” big ends for 1275 http://www.minispare...|Back to search

[DeadSquare]

 

My Mimispares catalogue only shows up to +.030". How recent is your information ?

+.060” big ends for 998 http://www.minispare...|Back to search

+.040” big ends for 1275 http://www.minispare...|Back to search

 

Thank you.  I'd better get a new catalogue.  I'll ring tomorrow and see if they also do +.060" main bearings.

[Cheeser]

I can’t recall the details now, it was about 45 years ago, but had a 1098 midget crank (2”main bearing) reground beyond normal undersize. A Triumph shell was used which was very slightly narrower and it also required the oil way to be slightly realigned. It worked a treat on this road engine!