I am restoring a Caterpillar 212 and would like to convert it to direct electric start. I have reviewed the parts book on the 3T and 79C machines and am thinking of using a bell housing from a direct electric start D-2. The part numbers are numerous. My concern is the flywheel. The numbers are one didget off. In reading all the posts, I have the impresssion that drilling and tapping the bell housing and bolting up a starter is what most people do.
Is that assumption correct?

The guy to talk to is Old Magnet on here as he has all the info on changeover to DES so I,m sure he will get back to you when he sees this post of yours.

I have had both, Pony start D2,s apart and also several years ago a 212 79C factory direct electric start grader apart but never thought too look at the differences in the flywheels? I think that the ring gear is different but am not sure beyond that. This will be interesting. Dave!

Hi Ages Cat,
I don't get around graders all that much but the flywheels would be slightly different to accept the bolting of the foot type clutch. As far as the ring gear goes they all used the same bevel tooth gear type. I'm also not quite sure whether the bellhousings are the same as the tractors but the starter mounting would be the same.
You can read up on the D2,4,6 conversions on my website.
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Be aware that around about 1959-1960, Cat changed the ring gear design from helical teeth to straight cut teeth for the pony start .. so that only one ring gear was required for both pony and DE.

If you have the straight cut teeth, you don't need to change anything - if you have the helical teeth, you need to acquire the nose adaptor to match the helical teeth .. or acquire and fit the ring gear with the straight cut teeth.

When I converted my pony start 12E years ago, I was fortunate enough to have the straight cut teeth ring gear already fitted. The MT40 bolted right up without any drama, and the only hard part was designing a battery box, wiring and cabling.

Hi Ozdozer,
I have not found that to be the case. Pony motors used bevel gear starters and flywheels throughout the life of the pony motors. Only if you ordered the later direct drive starters did you get the straight cut gears, all the way up through the D9's and the 11 or 12 tooth conversion pinion fits them all, along with the required drive end housing.

OM - That's interesting. Maybe the tractors were different to the graders .. or maybe it was relative to particular models. All I can go on .. is that my 1961 model Cat 12 (21F series - Aussie built), which was fitted with a pony from the factory, had a straight cut flywheel ring gear.

A check of the parts book for the machine, when I was doing the conversion, showed a change from helical teeth ring gears specifically for the pony (along with straight cut gears for the DE start) .. to straight cut ring gears for both pony and DE start, early in the 21F serial numbers.

The D644A of the same era is helical. Never seen a straight cut pony pinion gear. Always figured it was part of the design to make them work.

Thank you for all of this information. In researching the part numbers of the bell housings, I did find the housing called out for the D2 and the 212 DES have the same part number. Having had a D-2 with a pony motor that had a mind of its own, I will be converting the 212 to DES.