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Hello all,

New member here that recently posted in the main discussion thread. Looking for a set of 450 wide case bevel gears. If I understand correctly, I should ideally replace both the upper cam shaft gear along with the “lower” vertical bevel gear shaft that goes through the bevel tube to the bottom end.

Is it really, REALLY mandatory to replace both the upper cam and lower bevel shaft at the same time?

Reason being the only gear that’s chewed up is the upper cam shaft gear. The folks that were selling various sets didn’t have the right set/size and I’m having a bear of a time sourcing a set for my 450 wide case let alone the vertical bevel gear shaft. The vertical bevel gear measures-

202mm from peak of the bevel gears to the bottom of the semicircular shaft- or-
192mm from under the bevel gear to the bottom of the semicircular shaft

Fingers crossed hoping to find parts and also get some wisdom regarding how necessary it is to replace both parts…or can I just replace the upper cam gear?

Best,
Fpicabia

Just replace the long vertical shaft and the cam bevel gear as a matched set.
No need to replace the lower shaft and crank shaft bevel.
It is only the actual bevel gears that should be a matched set.
But, check that the coupling that joins the upper and lower shafts fits snugly.
You can buy various sizes of the short tube that slides over the coupling.
Or just replace the damaged bevel gear and take the time to shim it correctly.
Graeme

@graeme Thank you for the lightening fast response here! I appreciate the clear breakdown in your response. I'm a novice when it comes to understanding the mechanics of these engines. Perhaps I wasn't clear with my original question-

The long vertical shaft that goes through the bevel tube is the one that seems to be hard to find. The lower gears in the bottom end are in good condition. The only one of the gears that is chewed up in the whole bevel gear assembly is the upper gear that sides on to the cam shaft. It was the only one of the bevel gears that seemed to be damaged when the tachometer coupling seemed to have fallen off and broken off teeth of the cam shaft bevel gear before the previous owner shut the engine off. Wildly enough, the long, vertical bevel gear that goes through the bevel tube wasn't damaged at all. It appears that the semicircular coupling faces on both shafts, that connect near the base of the bevel tube, are in good shape. The tube that slides over the coupling to secure them in place seems to be fine as well. Whew. Though I will doubly confirm prior to reassembly.

If I understand you correctly, and it makes complete sense to me, one should ideally replace the bevel gears that interact with each other as a set. Though its possible to replace individual gears provided very special attention is taken to install and shim the replacement gear so both the replacement and the stock bevel gears line up as close as possible to the original position. Yes?

Lastly, are the upper cam shaft gears interchangeable with, say, 250 and 350 engines? Are the dimensions/cam shaft diameter/teeth count the same? I think I recall that they are NOT interchangeable but am hoping, hoping, hoping that I'm wrong.

Pardon the elaborate description here, I just want to be certain that I understand the options you described.

Best,
Fpicabia

You have a damaged cam bevel gear. How many teeth and what diameter is it ?
If everything else is in good condition? You could just buy another cam bevel gear.
But spend the time to shim it to get a good contact with its mating gear.
Not tight and not loose.
Take note where the timing dot is in relation to the key way or your timing will be out.
From the factory, the gears were installed and shimmed, then both mating gears had a grind mark showing where they mated best .
Another cam gear will possibly have the grind mark in a different position. (I don’t think the grind marks we're done by machine but by hand. So different gears may have the grind mark in a different place.
Good luck
Regards
Graeme

Hello and continued thanks to you @graeme for responding. My digital calipers are pretty good but definitely not Starrett or Mitutoyo and that’s why my dimensions are not exact. If necessary I can convert inches to mm with the set of Starrett analog calipers I have access to. Please advise.

The cam shaft bevel gear slid off the cam shaft surprisingly easy. There doesn’t appear to be any slop but should I be able to be slide it off with popsicle sticks and finger pressure vs a gear puller?

Question that might have been lost in the shuffle-
What are thoughts on stainless steel head/cylinder bolts vs stock steel. I have both.

Cam shaft bevel gear teeth count-
28 teeth

Accurate diameter measurement was compromised because a good number of the peaks of the teeth were chipped off.
C.S. bevel gear diameter from peak to peak of gear teeth-
48.90mm-49.00mm

FYI-
Actual Cam shaft O.D.-
14.85mm-14.95mm

C.S. bevel gear “sleeve” with key way thickness/depth-
12.65mm-12.75mm

I did find the bevel gear hand grind marks you referred to @graeme and if I understand correctly, the replacement cam shaft bevel gear grind marks will likely not correspond with my stock vertical bevel gear shaft. If I understand all this correctly, provided the cam shaft bevel gear is installed/shimmed correctly, the grind marks will not necessarily matter a huge amount?

Can’t thank you enough for all this information,
Fpicabia

P.S. If photo attachment files are too small, please let me know.

Where in the world are you ?
The cam bevel gear usually comes off easily (but not wobble on the cam loose)
I would just replace the damaged gear.
Where did all the chipped teeth go ?
Did you find all the chips in the oil ?
I would use the original steel bolts. If you use stainless in aluminium best to use copper grease or never sieze on the threads to prevent seizures later on. Stainless and alloy don’t go well

@graeme you, my friend, are a champion. I recently returned to the high deserts of the western United States to Orem, Utah after living in north Brooklyn, NY for about 40 years. I see you're in Tasmania, Australia? Beautiful. I have a handful of friends from eastern Australia that are in the surfing and music world. Great people.

I understand that Australia has quite a number of "vintage" Ducati and Guzzi afficionados. I do know I've envied some curved stainless Conti replicas that were well out of my budget when I was building a Guzzi some years ago. There nothing like the sound of a big block Guzzi with Conti pipes. Serious hot rod gear heads there, from what I gather.

Thanks for the responses re: the cam bevel gear ease of removal, etc. and the head/cylinder bolt question. I should've known the galvanic reaction between stainless and aluminum. Jeez, I did have that info in my mental files but for some reason it completely disappeared from the forefront of my mind. Might very well be due to the scrambled thinking that can come from a big move in living situations. Thanks for your patience.


Great, great news to hear your thoughts on just replacing the cam bevel gear. Are the cam shaft bevel gears interchangeable with the 250, 350 and the 450?


Oddly, I have no idea where the chipped teeth or the damaged tach coupling went. I'm actually quite puzzled/concerned about just HOW the tach coupling failed in the first place. I definitely do not want that to happen again. I can clearly see some damage done to the surrounding alloy area, primarily the lower spots where the bevel gears mesh. Luckily it's not too bad. I'll just need to smooth the area and clean every single thing out, top to bottom, REALLY WELL. I bought this bike quite a while back and when I originally drained the oil, I seem to remember that it was pretty iridescent so, yeah, I suppose I DO have a good idea where some of those chips went though I don't recall larger hardened steel teeth chunks in the oil. It was a few years ago. I have yet to dive in to the bottom end and hope that I don't discover a catastrophe.

Again, I can't thank you enough for sharing your knowledge.
All my best,
Fpicabia

Hello Fpicabia,
I know that discussing a problem can sometimes jog your memory.
I’ve heard of the tach drive bits doing exactly what yours did.
But luckily never to one of my 450’s
Probably why the long shaft bevel is very hard to find.
I personally don’t know if the 250 / 350 had the same cam bevel.
Is there anyone near you with Ducati single knowledge and tools,?
Might be worth looking inside the cases and the bevel tube to be sure that a chip isn’t going to damage something else. ??
Also be a good time to check and clean out the sludge trap in the crack.

Regards
Graeme

Thank you @graeme and agreed regarding questions/dialog and jogging memory. That’s not good news about the tach drive bits. Uh oh. Wonder if I should not use the tach and just listen to the engine/rpms or if there’s a better solution that someone figured out that’s more secure than the original stock coupling method. Hmmm. I definitely don’t want this to happen again. Especially given the apparent rarity of spare parts for the 450. Hmmm. Lucky you regarding your own 450’s.

What models do you have? Have you experienced and found a “solution” to the vibration I’m told is inherent in the 450 engine? Perhaps the heightened vibration in the 450 is partially the reason behind the tach coupling not being reliable? Someone in NY suggested a handle bar snake to at least minimize it in the hands…

Thanks re: clarification about your knowledge of the bevel gear dimensions. I’ll hopefully find the right size somewhere in the U.S.

I don’t know anyone near here with ANY vintage ducati experience let alone any vintage bike experience. I knew a bunch of folks on the east coast. I suppose I’ll either have to fabricate my own tools or source the more specialized ones elsewhere.

I will definitely be checking every nook and cranny inside all areas inside this engine and thanks for the reminder about the crank sludge trap. I’m not sure yet if I’ll have to separate/split the crank- a new concept to me- and remove the connecting rod to access the sludge trap but regardless, it seems like a “must do.” 2 part con rods I know, crank shafts that separate? Not yet…

Thanks again for your great communication and sharing info.

Best,
Fpicabia

Special tools for singles,
A good manual, the Haynes isn’t bad,
Clutch holding tool, you can make from old clutch plate,
Flywheel puller, available online. Note widecase and narrow case are different.
Good feeler gauges and micrometer.
Various shims and gaskets
Etc, etc.
Sludge trap can be removed without splitting the cases, but be careful not to push the sludge in.
Small magnetic pick and vacuum cleaner should work.
Look carefully inside the clutch cover and the oil pump / points cover for debris.
Maybe poke a magnet inside the bottom of the cases, see what comes out.
These engines are fairly simple to work on, just take lots of time shimming everything.

All 450’s vibrate, some more than others. I’ve seen a Scrambler engine vibrate terribly in the Scrambler frame but way less in an RT frame.
I’ve tried various different balance factors with varying success. Same balance factor, different bike,, different vibrations.

I think the later enclosed tach drive casting gave less trouble than the earlier made up version. But I have no proof of this.

I think I have a spare cam bevel gear ? But post to the US will be expensive these days.

Regards
Graeme

Ps, RT, ‘74 Scrambler, ‘74 Desmo, and a Desmo track bike. All 450’s