Crank bearings

I was wondering about the race motor that I am building, is there any reasons why I could not used sealed crank bearings? I would still use the crank seals but I thought that maybe using sealed bearings could be an advantage.
Thanks

Hi Andy,
The bearings will fail quite quickly, as the engine heats up the hot grease will get past the seal and there will be no lubrication at all.
Better to leave the bearing open and as close to the crank as possible so that it can get some mist from the crankcase. Most racers space the bearings so that they seat against the crank and use seals outboard of the bearings.
Good bearings will last a couple of seasons racing even with the highest of revving engines, a low revver will last 4 or 5 seasons. I use standard sized bearings and have no problem with them at all, some of the top racers modify to larger bearings... your choice.
See the drawings on the www.bsabantamracing.co.uk web site under bikes/tuning/general preparation, plenty of info there.
Cheers,
Alan

Hello again Alan,
Compliments of the season.
Busy rebuild x 2 motors here.
What are your thoughts on C3 or std clearance bearings for the crank ?

Hi John,
I thought you had gone to sleep john!
You must be getting ready for the festival in February? hope you have got that ignition sorted by now.
I prefer to use the C3 rated bearings where ever possible, but have found that they are a bit more expensive over here than the C2 rated.
You get really nice free running with these bearings, and they seem to hold the oil better with he larger clearances.
Let me know how things go at Pukie!
Alan