Bottom bevel gear removal

[Blimp]

Hi there, I'm stripping down my 250 scrambler engine. Almost there.

When removing the bottom bevel gear, the one with two angular bearings, is there anyway to remove it without removing the bearing housing and bearings?

Cases are split and crank is out, all other gears are out.

The bevel gear and shaft foul one of the bush bosses.

It seems likely I'll need to remove the whole housing and bearings, if so, whats the best way to do this?

Thanks

Blimp

[Rick]

To answer your 'best way to do this' question, the best way is with the factory tool. I'll attach some photos- the tool pulls the bearing cartridge out of the crankcase.
I remember a discussion of ways to push is out from the inside, but I couldn't recommend it. I spent my working life in machine shops, and more than once I've seen a good machinist trying to disassemble something that wouldn't come apart- frustration turns into anger, and in the wink of an eye it can turn into 'you SOB- you're coming apart or else' and out comes a big hammer or a torch- it rarely has a happy ending.
I'd suggest you find someone or a shop that has the correct tool- the bearings are expensive- one slip with a hammer and punch will wipe out what you save by doing it yourself.
I've pulled a few of these cartridges out- they're usually really tight- heating the crankcases didn't seem to help much, and even with the factory tool, about half of the time I only seem to catch 1 thread and I don't know if I'm going to pull the cartridge out or pull the top thread out.
Good luck, Rick

cartridge puller 1.jpg

cartridge puller 2.jpg

cartridge puller 3.jpg

[ducwiz]

This is my homemade extractor tool:

(click to enlarge)

It was made entirely from scrap parts. The bolt has a metric thread (10 or 12mm) and screws into the lower part, which in turn fits into the bush's thread, covering as much turns as possible, with no danger of ripping off the thread. Sometimes with quite vigorous hammering, it extracted a lot of bushes, even those seeming to be pressed in. No heat was applied to the engine cases for the job.
However, you need a lathe to make the outer thread, or a good friend or mechanical workshop round the corner ..

cheers Hans

[Blimp]

Thanks both, great info, but do I have to remove the housing in order to remove the gear? It seems like you should be able to take it out to replace the gear without taking out the whole thing?

Thanks

[dsmess]

If you are replacing the bearings in the crankcases (electric convection oven at 300f worked for me) the housing should drop right out. To remove just the gear you need snap ring pliers. Keep track of shim locations.
Dave

[Rick]

If you just want to get the gear out of the bearing cartridge you'll only need to lift it up until you can avoid hitting the oil pump casting- it doesn't need to come completely out of the crankcase.
I just remembered the other thing I don't like about driving the cartridge out from the bottom- I had one that was mushroomed out from someone beating on it, then they pounded it back in and got everything out of alignment- big mess.
Rick

[Blimp]

Many thanks all. Much appreciated.

[ducwiz]

Rick,

I'm interested in a comparison of the lower thread on our extractor tools. I identified and in turn fabricated it as 36.5x1, metric size. Could you please measure yours?

tnx/cheers Hans

[Rick]

Hans,
I would say 37x1, mine measures 36.9 outside diameter. Mine is definitely a tight fit into some of the bearing carrier cartridges, but fits others fine, so I've always thought the tight cartridges were compressed into a crankcase bore that was too small- can't recall if I ever checked if the tool fit better after the cartridge was out. I think mine is a factory tool, but I didn't get it from Ducati so I can't be certain.
Rick

[ducwiz]

Thanks Rick,

seems both diameters work. Mine feels a bit loose in some of the cartridges I screwed it in, yours has obviously a tight fit.

cheers Hans