Series 1 Crankshaft Bearing Qusetion

[Cosmic Wizard]

Morning all,

Just a quick question regarding the early Series 1 Crankshaft and mag bearing. I have removed the original mag-housing & bearing and replaced it with the 'normal' type and also fitted a new bearing, spacer ring and seals.
Are there any differences between the early Series 1 Crankshafts and the later standard LI Cranks?

The reason for asking is, I had assembled the mag housing in the following, correct order; outer seal, seal retainer plate, bearing, spacer ring, inner seal and circlip. When I refitted the mag-housing and flywheel, there was alot of play, even after tightening the flywheel nut. Thinking I'd got the order of parts wrong, I stripped the housing and refitted the parts in this order; outer seal, seal retainer plate, spacer ring, inner seal and circlip. This has sorted the play out, but is it right?

The engine will receive a proper rebuild in the future, but I just wanted to get it running, hence the seal and bearing replacement.

The only other thought I had was, should I have fitted the wider GP bearing?

Anyway, just thought I'd ask as I'm curious.
Cheers
Jim

[Warkton Tornado No.1]

I stripped the housing and refitted the parts in this order; outer seal, seal retainer plate, spacer ring, inner seal and circlip. This has sorted the play out, but is it right?

Where is the bearing? I'm guessing that you have actually fitted it just outboard of the inner seal.

You appear to have successfully updated the magneto bearing to a 'captive sleeve on the crankshaft journal type' as adopted for S2 onwards which I believe has the same 'geometry' as the earlier arrangement.

So, for what it's worth I think you have got it right

[Wack]

The shoulder on the Ser1 crank is only 8 mm, whereas Gp’s are 12 mm. Therefore the bearing inner race won’t run correctly on the rollers I seem to remember. Done a few motors using the Ser1 mag and used a ball bearing and petrol lube with a machined down GP crank.

[Warkton Tornado No.1]

The shoulder on the Ser1 crank is only 8 mm, whereas Gp’s are 12 mm. Therefore the bearing inner race won’t run correctly on the rollers I seem to remember. Done a few motors using the Ser1 mag and used a ball bearing and petrol lube with a machined down GP crank.

I'd forgotten about the shoulder differences

It's a long time since I had to use a S1 magneto housing, but I must have made a tubular spacer to enable use of the NU type roller bearing. I know that some race machines use ball bearing races on the flywheel side, but I prefer the roller bearing as it not only copes with higher loads, it allows for axial differences between the crankshaft & housing, which continue to exist due to thermal expansion rates. However, I would say that the NU bearing functions just as well when lubricated by the petroil mix, which might appeal to those that wish to lower the primary compression ratio. IMHO a very worthwhile modification.

As far as Cosmic Wizard is concerned, the axial geometry needs checking, which @ most will involve a Vernier or Digital caliper.......