crackshaft bearings

[dougi]

hi all
i am about to rebuild a 1980 3 1/2 engine which i got for free but in bits ! the crankshaft has a ball bearing on one end and bush on the other end . i will be replacing all ball bearing but i do,not know if the bush bearing is useble. i need the tolerances of the crankshaft bushes.how can i find the tolarances.i have manual it tells big end sizes but not main bearing sizes

[3potjohn]

Some have replaced the bush with a roller bearing, I think this is an improvement over the bush but will require some work on the crank to accommodate the bearing etc. Haven't got any spec to help you,maybe ring NLM.

[EVguru]

Note that the ball race probably has a C3 clearance. The main bearing specification might be in one of the later manuals, I'll check at home.

The roller bearing conversion is worth doing on early engines (since it just drops in), but with later engines, I'd only bother if you're going to tune the engine. You have to grind the plain bearing journal off the crank and that's a lot of grinding.

[TonyH]

Hi Paul (or anyone else for that matter), i know this thread was a long time ago but i'm about to rebuild my early 350 and wondered where i would get the Roller Bearing Conversion you mentioned from? Is it the one offered by NLM?

Many thanks, Tony

[EVguru]

I'm about to rebuild my early 350 and wondered where i would get the Roller Bearing Conversion you mentioned from? Is it the one offered by NLM?

Yes NLM can sell you the bearing and arrange to have your crank ground to take it if it's the later plain bearing type. The bearing itself is just a standard roller type NU206 with C3 clearance. If you really want the best then one with a steel or bronze cage would be ideal.

Here's a couple of pictures of the bearing from Raymond Hamaker photo site;

http://mantaray.zenfolio.com/p396126308/e43d049e
http://mantaray.zenfolio.com/p396126308/e4d5c059

I buy most of my bearings from http://www.simplybearings.co.uk

[TonyH]

Thank you very much for advice and prompt response. Tony

[hombre]

but not main bearing sizes?

They are in the blue book (page 78 ). You can download it here; http://www.olisystem.it/morini/Service-Manual.pdf

In my Camel I had the bearing (the inside ring) replaced by a machineshop with one from a Toyota Hiace camshaft. You can buy a set of 5 rings which have almost the right diameter. They're too wide but my machineshop made them smaller. One of the rings is not usable because it has an oil channel so it won't maintain it's pressure. I hope i explained it right. it's worth while since the rings are way cheaper than the orignal bearing (and you can do 4 bikes at the same time )

[mantaray]

Here's a couple of pictures of the bearing from Raymond Hamaker photo site;

http://mantaray.zenfolio.com/p396126308/e43d049e
http://mantaray.zenfolio.com/p396126308/e4d5c059

url changed to
http://mantaray.zenfolio.com/p573222433 ... 9#h4d5c059
and
http://mantaray.zenfolio.com/p573222433 ... 9#h43d049e

Next time i use the NJ 206 M with bronze cage

[mantaray]

This are the ones with bronze cages

NJ206-E_M1A C3 and Qj306MA

_A021973small.JPG (29.82 KiB) Viewed 12581 times

[Alfonso70]

Hi, sorry to ask what is possibly a obvious question, but is there any difference between to two types shown? Which ones are best? the roller type or ball?

Thanks, Tony

[EVguru]

Hi, sorry to ask what is possibly a obvious question, but is there any difference between to two types shown? Which ones are best? the roller type or ball?

Thanks, Tony

The roller bearing replaces the timing side ball race on an early engine or the plain bearing on a later engine (requires grinding the crank).

The FPAC (four point angular contact) bearing was used on the 500 engine rather than a plain ballrace. Although it's really designed to take axial loads, it also has a higher radial load capacity compared to a standard deep groove ballrace. It's probably overkill on a 350 engine, but it does make dismantling the engine much easier because the inner race is seperable.

FPAC bearings were also used in the 500 gearbox.