Bevel Drive Housing

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old guy
Posts: 5
Joined: Fri Mar 16, 2018 9:38 pm
Location: southern California

Bevel Drive Housing

Postby old guy » Sat Mar 17, 2018 4:02 pm

As a first timer to the forum I appreciate the opportunity to learn from your collective knowledge. I am in the process of rebuilding a mid-60’s 250 Ducati scrambler with an unknown history. It had a tremendous amount of crud on it yet the standard bore piston seems to be within spec and other internals look good despite a sludge trap that was completely blocked. I got the cases are apart and am selectively replacing bearings. Without much ball bearing experience, I am tempted to leave smooth feeling bearings in but the new bearings feel so much better. My first bearing replacement went well (main bearing) so I am tempted to replace them all. My immediate concern has to do with the lower bevel bearings and the housing. I don’t know what to expect with respect to housing removal or disassembly and welcome a recommended approach. It seems to be a tight fit and I don’t want to break anything. I am tempted to leave it alone, but want to be thorough. The manuals assume a factory gear puller type tool. I have not seen one for sale and cannot think of a way to make a substitute. I would think its removal and installation is desired to adjust the mesh of the lower bevel gears without spitting the cases. Any thoughts?

I have been postponing the head work, but can see an issue. The exhaust port threads are all but disappeared. The exhaust pipe had been attached via spring to a nearby cooling fin. I cannot imagine that is satisfactory, but others must have had this problem. Any recommendations?

Bevel bob
Posts: 1042
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: Bevel Drive Housing

Postby Bevel bob » Sat Mar 17, 2018 5:15 pm

Hi, I replaced my bottom bevel bearings, I warmed the cases and using an alloy drift just tapped out the housing from below ,I had to tap on the center of the gear and it probably was not good for the bearing ,but as it was being replaced no issue. Bearings that spin silently and smoothly after cleaning are usually good.

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: Bevel Drive Housing

Postby ranton_rambler » Sat Mar 17, 2018 5:38 pm

For my money, I would replace all of the ball/roller bearings while the cases are apart. In relative terms they don't cost much, except the big end.
Mine felt OK (ish) but once it was apart I was very glad I'd decided to have a look.
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Bevel bob
Posts: 1042
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: Bevel Drive Housing

Postby Bevel bob » Sat Mar 17, 2018 5:47 pm

Some of the bearings are angular contact specials. Be carefull which way they go in. Be prepared to spent lots of time getting the shims right.

Eldert
Posts: 771
Joined: Sun Nov 01, 2009 3:23 pm
Location: Hazerswoude Rijndijk Netherlands

Re: Bevel Drive Housing

Postby Eldert » Sun Mar 18, 2018 9:54 am

about the bigend bearing / pin new silverplated bigend bearings are for sale in Italy

on EBay.com some lady is selling the leftover narrowcase bigendpins from her late husband Joe from Eurorods
i bought 2 and they cost me 94 euro a piece shipping and customfees included .


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Eldert

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: Bevel Drive Housing

Postby ranton_rambler » Sun Mar 18, 2018 10:38 am

Thanks Eldert, but the inside surface of the rod was also damaged. I have had a rod refurbished with hardened sleeve pressed into the rod and a new pin made. I believe that many of the pattern rods are not very good, and I could not find an original one to use.

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: Bevel Drive Housing

Postby double diamond » Mon Mar 19, 2018 6:01 pm

In some engines, the lower bevel bearing cartridge slides out of the cases with little to no effort. On others, the factory cartridge puller is mandatory because the cartridge is so tight in the cases. If you have the cases apart, you can heat the cases in an oven at about 350 F and the cartridge might slide out. You want to heat the cases anyway if you choose to remove the transmission bearings. Do not remove the outer race for the countershaft in the left side case (this is the bearing with loose rollers that ride in the groove in first gear). The race is staked in place; if you remove it, you’ll have pieces of the case where it’s staked chip off. This race is not available anyway, so no point in removing it. You’ll probably need a blind bearing puller to remove the right side clutch shaft bearing if it doesn’t just drop out when you heat the cases.

If you only wish to remove the lower bevel bearing to inspect/clean, it might be possible to push them out of the housing in situ. The bearings are not a tight fit; gentle tapping with a brass drift might be sufficient to remove the bearings from the cartridge. In order to shim the lower bevel, you have to be able to withdraw the lower bevel bearing cartridge. The lower bevel shaft gear cannot be removed from the cases with the crankshaft installed but the bearing cartridge can. So you remove the cartridge to change the lower shims if necessary, reinsert the cartridge, shim the play on the upper end of the bevel gear, install the circlip and check backlash/contact. I recently shimmed the lower bevel on a widecase 350. It would have been impossible to do without the extractor tool since the bearing cartridge was such a tight fit in the cases. I got this tool from Ian Gowanloch in Australia. I believe he had several of these tools, so if you decide you need one, Ian is worth a try. I would caution you to have him check the condition of the threads that engage the bearing cartridge on the tool he sends you. The threads on the tool I received were damaged and had to be cleaned up on a lathe. But before you go to these lengths, assemble the bevels with the original shims. You might get lucky and the factory shimming is OK. “OK”, of course, is dependent upon how meticulous you are. You’ll be amazed how much difference .01mm makes in setting backlash. If you don’t have an adequate selection of shims, the point is mute.

If your sludge trap was completely plugged, I would recommend you remove the welch plugs in the big end pin and make sure the inside of the pin is clean. The same 350 I’m assembling had A LOT of debris inside the pin even though the bearing journal looked OK. If there is debris inside the pin, the crankshaft should come apart to be inspected. If there is any sign of water entering the lower end of your engine, it would warrant disassembly and inspecting the big end components. Even if the big end feels OK, water may have made its way into the bearing and you end up with rollers that look like Ian’s. At the very least, the thrust washers will probably be worn and would benefit from replacing.

Matt

old guy
Posts: 5
Joined: Fri Mar 16, 2018 9:38 pm
Location: southern California

Re: Bevel Drive Housing

Postby old guy » Fri Mar 23, 2018 2:12 am

Thanks for the info. I had a further question regarding removal of the welch plugs in the big end pin and splitting the crankshaft. What is the best approach to removing the welch plugs? Punch it out? Drill? Presumably removal destroys the plug. I haven't seen the plugs advertised. Is it a generic item commonly sourced?
Also, I never have seen much discussion about actually splitting the crankshaft. The Haynes manual says to send the complete crankshaft to a Ducati agent for repair; it is beyond the scope of the average owner. Very accurate trueing is necessary entailing specialist equipment. I have seen ads for rod/bearing sets but not for assembly. This seems like a core issue for these engines. Is this a common machine shop practice?

Samurai
Posts: 137
Joined: Wed Nov 28, 2012 9:53 pm
Location: Somerset, U.K.

Re: Bevel Drive Housing

Postby Samurai » Fri Mar 23, 2018 7:16 am

I had my crank stripped and inspected by Brian Silver of Moto Marianna, a Ducati Singles specialist here in the UK. However I understand that he has now retired due to ill health.

I believe you need a hydraulic press to actually get the crank apart and the knowledge and skill to align and reassemble it. Seeing as this is the heart of your engine, I would strongly advise that you give the job to a specialist engineering shop unless you have the necessary equipment and skills.

It won't be cheap, Brian was very reasonable and I was charged about £600 or so to strip and inspect the crank, to rebore the cylinder and supply a new piston kit to match.

As it happened, he found it has probably been rebuilt shortly before I got the bike and the crank and rod were in good order. However it was peace of mind before I started throwing even more money at it on parts!

Eldert
Posts: 771
Joined: Sun Nov 01, 2009 3:23 pm
Location: Hazerswoude Rijndijk Netherlands

Re: Bevel Drive Housing

Postby Eldert » Fri Mar 23, 2018 8:16 am

the welch plugs are a generic item . i buy then in a box of 20 .

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Eldert


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