Plastic pump gear?

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aerojack7654
Posts: 17
Joined: Thu Oct 22, 2015 1:39 am

Plastic pump gear?

Postby aerojack7654 » Thu Aug 03, 2017 1:47 pm

Hello all,
It's been awhile since I posted anything on my long rebuild of a '71 350 frame and engine, the engine having been built for racing and then put on a shelf never having been run. It's pretty well done now, as shown in the pic (polished aluminum fenders have been added since then), and I've been diligently working out the carburetor situation since the thing came with a brand new 34mm smoothbore Amal that I chose not to use for a street application. I've almost homed in a 32mm Mikuni configuration, still a tad rich, working my way through JetsAreUs jets. The event that prompts this post is that as I was starting off to work the other day (my first actual functional application of the bike) and after about 100 yards the bike just shut off, not to be restarted. Pushed it home and after inspection that night, there was no spark, and I tracked it down to the Sachse ignition module not firing. Pulled the cover and the unit was lit up, but the rotor shaft wasn't spinning as the engine was kicked over! Further disassembly revealed that the oil pump gear had disintegrated - it was plastic, old and brittle at that.
I've found an NOS gear (metal) in France and it's on it's way, but my question is what possessed Ducati to put such a thing in there? It seems like all the other gears that I've been able to find are metal. I'd have to also question why the folks that built the race motor (the former Europarts in Florida), after putting a lot of very expensive other parts in the engine (which had been running really well to this point) left an old plastic pump gear in it?
I guess I'll be looking for all the gear train alignment links here soon...

Regards,
Jack
Shine.JPG

Jon Pegler
Posts: 217
Joined: Sun May 16, 2010 6:19 pm

Re: Plastic pump gear?

Postby Jon Pegler » Thu Aug 03, 2017 2:13 pm

The plastic oil pump drive gears were fitted as standard by Mototrans in Spain, but never by the Italians in Bologna.
It is always worth replacing a plastic gear with a steel gear as they are so prone to failure.
At least when they do fail the points drive gear stops turning and the ignition cuts out, before any damage is done.
One thing to check on your replacement steel gear is that the shaft length is the same as your existing plastic gear, or shorter.
There are two different lengths of shaft.
For those who want to retain a plastic gear, new reproductions are available in Spain.Quite who would want one, I don't know.

Jon

aerojack7654
Posts: 17
Joined: Thu Oct 22, 2015 1:39 am

Re: Plastic pump gear?

Postby aerojack7654 » Thu Aug 03, 2017 2:34 pm

Thanks for the info Jon, I was suspecting that it might have been a Spanish thing. And thanks for the info on the shaft length - I'll definitely compare when it shows up, but as far as finding any of these things it appears that the options are limited - I found one at Back to Classics for 90 euro (no mention of the shaft length and not sure of the application) and the one on ebay for 25 euro, with no coherent application other than "250, 350, 450". My list of other US and European vendors didn't appear to stock the things (probably since metal ones don't break?). I don't want to replace with another plastic one, that's for sure!

Thanks!
Jack

ducwiz
Posts: 186
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Plastic pump gear?

Postby ducwiz » Thu Aug 03, 2017 6:15 pm

Old gear's shaft length = 34mm, new one 28mm (from gear to shaft end).

...

aerojack7654
Posts: 17
Joined: Thu Oct 22, 2015 1:39 am

Re: Plastic pump gear?

Postby aerojack7654 » Sat Aug 12, 2017 11:05 pm

Hi guys,
Got my metal gear installed and I have a question about the timing. I've got the dots lined up on the top and bottom bevel gears, so my question is can I now align the oil pump gear so it's dot lines up with the dot on the gear on the crankshaft, and then align the points shaft gear in so it's dot lines up with the oil pump gear. Does this satisfy the gear alignment situation in order for me to go on to the engine ignition timing? Or does the engine have to be at some other condition as well, like TDC, for example, along with the dot alignment.

Thanks for your help
Jack


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