Remove the bevelshaft without dismounting the crankshaft?

[Rocla]

Hi,

I've suggested this topic because I am struggling for removing the bottom bevel gear and the bevelshaft too. Both are dented. I've removed the 2 bearings housing, everything is ready but there is not space enough to remove the bevelshaft... It normally requires to dismount the engine housings.

But if you see on this picture here below, it is quite amazing because such inverted cast "tower castle" seems too big in comparizon with its purpose. Given it contents a steel bearings guide insite, why a so big dimension? If you drill the blue colored part, it enables to remove the bevelshaft without dismounting the engine, and as I see it, without damaging the global resistance...

Is there somebody who tried such modification? Some points of view?

Dsc04950B.jpg

On my opinion, I prefer a modified engine housing with a brand new bevelshaft than a genuine housing with a dented bevelshaft pinion. Am I really wrong?

[Bevel bob]

Sorry Rocla, my memory let me down. have you tried re-shimming the gears to see if they can work? ,At least you can change the shimms now,although its a bit fidlly.Thit type of gear has a fair area of tooth in contact and the wear may not be significant.

[LaceyDucati]

Rocla

Yes a real oversight of design, but bottom line is if you want to remove the bevel you will need to split the cases.

I would loose that plastic timing gear before you rebuild your engine as they are prone to failure and easily replaced with a steel one.

Best Wishes Nigel

[Jordan]

There is a tool for removing the bottom shaft/bearing housing. It screws to the top of the housing, then pulls it out after preheating the aluminium.
I think, when these bikes were low cost (a new Monza cheaper than a Honda CB250 once) then crude methods of removal with improvised tools was justified.
But now that they have become so valued, it's time to reconsider improvised methods that can be risky. Also, it's so nice to work when you have the proper tool. If you can't buy one, make it. Or, give the job to someone who has the equipment.
A sketch can be provided so you can make a tool, or have it made, on a screwcutting lathe.

[Rocla]

Hello both and thanks for your replies

Jordan : The bottom shaft and bearings housing are already outside. The problem is relating how to remove the bevelshaft... And I am sure that metal resistance doesn't need a so strong aluminium tower around this bearings housing. It is a little bit shamefull that just for 1 or 2 cm, dismounting the bevelshaft requires to dismount all the engine... And I was wondering if somebody already experienced this modification (to know the best place to drill as little as possible).

Lacey Ducati : I agree, it is a mistake from the designer. Another is to have designed a so pointless aluminium tower around the bearings housing. But it seems that nobody shares my point of view

Bevel Bob : I can adjust the shims, I've planned that (in canceling 1 vertical shim and 1 or 2 horizontal ones) of course but I need more : some teeth of the bevelshaft are dented. Given the rest of the engine is in a very good condition and will last, I want to replace the shaft. Unfortunatly, 1 or 2 cm of metal empede me to do so...

[Jordan]

Hi Rocla,
I see now you've progressed more than I thought, with the bearing assembly out already.
I had to look up a drawing, to remind me that the bottom bevel gear doesn't lift out with that assembly.

OK - now please do reflect on your proposed workaround for removing the gear/shaft without splitting the crankcase by some inventive surgery!
It looks like it might well work, but if I may use a technical engineering phrase, "It isn't nice!".
Splitting the crankcase may seem distasteful, but won't you need to do something about the stripped thread on the crankshaft anyway? (metal spray?)

I know some very keen Ducati bevel enthusiasts who would buy a V twin brand new, then take it home and routinely dismantle the engine to check and improve the factory shimming (especially gearbox).

[LaceyDucati]

Plus one with the not being engineeringly nice and more the point not really necessary. Stripping the bottom end beyond this point is relatively easy and could be all done in less time than the planning and discussing this mod.

You would also probably need to strip the the engine after the ingress of all the aluminium swarf you create gets in the engine. Either sooner or later!!

Sometimes the correct solution is simpler in the end!

Nigel

[StewartD]

Hi Rocla,

I agree with Nigel and Jordan that cutting away this part of housing is a drastic step and 'not nice'

You've already done the top bevel gears. This is one of the hardest jobs on a Ducati. You are now fully qualified. Don't be intimidated about splitting the cases. It really isn't that hard.

First remove the countershaft sprocket and the crankshaft bevel gear nut. If you are only doing this to fix your bevel gear problem, then I think you can leave the clutch and primary gear in place. I haven't done this for over 20 years, so if anyone can correct me, I would welcome the input. It will make the job easier if this is the case. Taking the primary case off, will make the cases easier to sit down in a stable manner.

Next sit the cases, with all the main shafts vertical, on a couple of large blocks of wood, with the primary drive side down. Undo the 5 M6 socket head screws and the 2 cylinder base bolts. If you are careful about easing the cases apart then the multitude of gears will stay on their respective shafts, and the shafts will stay in the bottom case. The crankshaft, due to its weight will almost certainly stay in the bottom case, even if you have taken off the primary gear. The gear selector shafts may come adrift but if you lift vertically, the selector forks will probably stay engaged to the gear grooves.

If all the shafts have stayed in the lower case, check the inner races of the bearings on the upper case. There might be shims that are stuck to the bearing inner races. Remove these and put them over the end of the correct shaft in the lower case.

Voila.

Stewart D

[Rocla]

Hi again,

Shame on me, I did it!

So, facing your comments, I feel guilty and forced to justify my behaviour:
- even if I am a little bit more experienced with Ducati, I am still intimidated with splitting the cases (it requires tools and time I don't have)
- of course, I could only change the crankshaft bevel pinion but the vertical pinion was dented too, and it was my priority to ensure a long life to the engine. I prefer an ugly right case (for the sad fews that know how it is inside) with a sustainable bevel mecanism than a perfectly genuine right case, and a very dented bevelshaft pinion...
- when I drilled the case, all the parts inside (crankshaft bearings, oil ducts) where serioulsly protected by the mean of adhesive tape and clothes
- before knowing that it will empede me, I was atonished by the so strong and big tower that encloses the bevelshaft bearings housing. Why a so big cast? Just for 2 cm of metal, it wasn't possible to remove the bevelshaft without splitting the cases, that sounds like an design error. My decision was easy to make: as I see it, there is no risk, only advantages. Furthermore, have you seen, nobody in the forum replied on technical risks. I think it was only a matter of principles comments... Dont' you think?

But I confess it is not a gorgeous solution. I beg your pardon

[Jordan]

You rotter! I will never speak with you again.

Actually, that was quite brave, but I will not follow your example.
May we have a photo of the result?
We'll be interested in reports good or bad.