Remove the bevelshaft without dismounting the crankshaft?

[Bevel bob]

You have gorn an dunnit now!!. Ducati should have incorporated a cut out in the design, so you can blame them. We are still unsure how this helps you get over the thread problem. One thing that will not work is to leave out the shim behind the crank bevel to access more thread. This will put the gears out of mesh and load up the shaft joint stopping the head from seating, guess how i know this. I suspect that the gear damage was caused by the bearing bushing being free to move up ,missing shim from the top??.

[Rocla]

Hi,

Bob: I removed the bevelshaft only because its pinion was dead. Changing the setup doesn't need to remove the shaft, just the bearings housing and the circlips. By the way, the thread was OK, it was mainly the nut that was damaged, fortunately. So, no welding spot! Concerning the setup itself, I've did many trials, with many shims dimensions, upt to the point I reduced the play (just a tiny play but no noise or almost) while the rotation remains free. Anf I've replaced the bearings and the circlips, in addition to the bevel gear itself. You were right, one of the two bottom bearings was fired, and the 2 circlips as well... I did my best to ensure maximum longevity to my engine

Jordan: here below the picture of the (petty ?) crime

Dsc04982Z.jpg

And more details about the bevel gears setup here below on my webpage (almost real time updated):

http://strv.pagesperso-orange.fr/motode ... Ducati.htm

[Paddy]

Does the OP realise the bevel gear comes out the top ?
slacken the 4 head bolts, undo the top bevel bearing casing, lift head and bevel tube remove bottom bevel tube o ring housing, remove bevel tube, bevel shaft and top bearing.
Withdraw bottom bevel unit using the puller available for the job.
20 mins max.
Or have i misunderstood something

PS as nigel says.lose that plastic gear,i have spare steel gears.
As for butchering your cases like that ? I'm speechless.

[Jordan]

Thanks for the photo.
Ouch!

Your gear mesh is good, but I'm worried about the outer edges of the teeth relative positions.
They are usually much closer to being on the same level - yours look to have about 1mm step?
That may change the valve timing, due to the helical tooth shape. Bad news would be power loss or valve-piston contact.
But, maybe it's OK, even if cam timing is altered a little.
The mesh can also be good if shimmed so as to move the tooth edges closer together.

Jordan

[Bevel bob]

Hi Paddy, I had the same thoughts, but i was also wrong!. The gear mesh does look very wrong , but we are (i think ) seeing an unmatched and unground pair, not something most ever use.As long as the tooth contact patch is good (blue the gears) it should work , i would check them after a few K miles as they may wear in.(or out!).

[StewartD]

Gear teeth terminology.jpg

Hi Rocla,

If the faces do not have a ground flat to enable them to be fitted flush, you still must try to get both gear's (cone shaped) end of tooth surfaces to be mutually flush.

Gear teeth are profiled to an involute curve. Check the attached diagram. Note the Pitch circle of the two gears; they only intersect at one point. (Pitch circle diameter of two gears divide by 2 gives the gear centre distance). In the diagram the gear teeth are in contact at this intersection point. When the gears rotate a small amount the contact point will move to a point closer to one gear's tip, and at the same time move to a point, on the other gear, closer to its centre. The geometry of an involute curve ensures that the rotation speed of the driven gear is in constant proportion to the rotation speed of the drive gear.

As bevel gear teeth are cut to a base surface that is conical, the outer end of the teeth are thicker than the inner end. If the gears are not as closely matched, regarding the tooth thickness or profile, as possible then the teeth will not smoothly engage and disengage in the way they are designed too. Not having your gear's end of tooth surfaces mutually flush will means there will be as mismatch between the drive gear and the driven gear's tooth thickness and involute geometry.

The wear will be high and they will be noisy as well. This is a job worth doing well.

Cheers,

Stewart D

[Paddy]

Also.......dont follow the link to his sight as it is infected with Malware.

[Rocla]

Hello everybody,

The picture I've displayed was not with the last bevelgear setup. I did many trials to minimize the plays and the noise. Here below is the last one, without any noise, just a little play (it turned freely)...

Dsc04977.jpg

Here below the bevel gear of the camshaft. The noise is barely audible (the headcylinder was still apart from the engine)

Dsc04971.jpg

I've remounted the engine on the bike. All the gasket are OK, the oil too. Everything is OK except for the ignition: there is no spark at all. I have to fix that (it was the cause of the problem I've got when I was coming back from my holidays trip in August)

[machten]

That's still a long way off what a bevel gear alignment should look like.

Here below is the last one, without any noise, just a little play (it turned freely)...

Maybe, but compared to what? (what you've heard so far probably isn't too good) and under what conditions (no compression, no load, no valve spring induced backlash, no RPMs)?

I'm with what I think StewartD is implying (correct me if I'm wrong StewartD)...there is some small chance those bevel gears could mesh well looking like that, but the chances are small. Worth a try perhaps, but assess before running too far at all would be my advice, and I'd be very suprised if you didn't have some noise through either meshing issues themselves or lash through to the to the top end (which adds from the bottom bevel lash + oldhams coupling lash + top bevel lash)

Of course....you could be lucky!!!

Kev

[Bevel bob]

I hope you gave it all a good wash-out, plenty of crapp in there, also i would think about fitting a roll pin restrictor into the bevel end of the cam to give a bit more oil to the cam/rockers,The bottom gears looked like they needed shimms removing from both gears.