Ser 1 crank

[Wack]

I want to upgrade a crank in a Ser 1 to still use the original mag housing with the petroil lubed flywheel bearing but I don't have an original crank to hand so wondered if anyone has one and could measure the shoulder depth on the web so I can machine the new crank to match.

[Knowledge]

Interesting. I don't have the measurement you require, but I do know that Charlie Edmonds developed the Super Monza with the intention of having the flywheel side bearing lubricated by petroil, rather than grease. Therefore, I assume that Charlie saw petroil lubrication as an improvement.

The mag flange was altered to something like the SI item.

Having said that, I have heard of no one else bothering with this change when they fit the SM kit.

[Warkton Tornado No.1]

Ser 1 crank
Post by Wack » Sat Aug 13, 2016 5:49 pm

I want to upgrade a crank in a Ser 1 to still use the original mag housing with the petroil lubed flywheel bearing but I don't have an original crank to hand so wondered if anyone has one and could measure the shoulder depth on the web so I can machine the new crank to match.

I do not have a SI crank to hand, so it may be that you have to offer up the crank you intend to use with no bearings or seals fitted in the magneto housing to check fit.

I think you may find that very little, if any, modification will be required.

Apart from utilising an NJ (as opposed to NU) bearing, I think the geometry of the crank end will be similar. You may need to make a spacer ring to allow the circlip to retain the bearing outer within the magneto housing.

I would recommend you use an NU2205 if you want to keep with a roller bearing. It certainly is a modification that I have done, but, what with racing sometimes being a little secretive, I cannot say to what extent others may have done the same.

However, I believe that for some time, eliminating the inner seal of the magneto housing & even substituting the roller bearing for another type are/were relatively commonplace in racing two stroke engines. However, one of the objectives realised in doing so is to increase the crankcase volume & lower the primary compression.

Of all the bearing catalogues that I have utilised for years, the speed rating of any such type of bearing will also be greater when lubricated with oil than with grease.

I hope this helps....

[davej]

May have one, I'll have a look in morning.

[davej]

Have one! What is the actual dim you require ? Can you pm me a sketch ?