C3 crankshaft bearing

Hi All:​

Please, two questions:​

1. what is the difference between a cranckshaft "C3" bearing (Fag-30x72x19-NJ306-E-XL-M1A-C3) or not "C3"?.
2. is a good match to use a drive side roller bearing (Fag-30x72x19-NJ306-E-XL-M1A-C3) with a timing side ball bearing (FAG-30x72x19-

QJ306-XL-MPA-C3)?.​

Thank you.
Piero

pierodn said:

1. what is the difference between a cranckshaft "C3" bearing (Fag-30x72x19-NJ306-E-XL-M1A-C3) or not "C3"?.

Click to expand...

A C3 bearing (either ball or roller) has more internal clearance than a standard bearing and C3 is the recommended bearing for a Commando crankshaft.

pierodn said:

is a good match to use a drive side roller bearing (Fag-30x72x19-NJ306-E-XL-M1A-C3) with a timing side ball bearing (FAG-30x72x19-

QJ306-XL-MPA-C3)?.​

Click to expand...

For what, exactly?

The bearing prefix C3 means a clearance (gap - roller/ball to race) as opposed to other bearings.
C3 is more accommodating to misalignment and temperature increases than other bearing classes (eg: C1, C2)
There are risks in using C3 where the clearance is not required - can cause skidding and premature wear.
Not sure about your specific questions but I believe C3 to be a "safe" specification for Norton main bearings

BTW - I was not aware of commandos using balls on the drive side - thought this to be pre-commando heavy twins (and singles).
Those earlier bikes used single row ball plus parallel roller on the drive side.
I am not aware a a ball bearing being used on the timing side.
Cheers

robs ss said:

I was not aware of commandos using balls on the drive side - thought this to be pre-commando heavy twins (and singles).

Click to expand...

Piero asked about using a ball bearing on the timing side (as Commandos had pre-200000, NM17822, MJ30).

pierodn said:

I asked if is a good job to fit a drive side roller with timing side ball bearing.

Click to expand...

Yes, but for what?
If you mean a Commando then personally, I don't see any logical reason not to use two roller bearings.

The QJ306 is an angular contact bearing.
I don't know if there would be any reason to use an angular contact ball bearing in place of the standard NJ306E roller.
The QJ306 MA (MPA?) is a 'Duplex' ball bearing with an inner race in two half sections.