Conrod kits ?

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Bevel bob
Posts: 764
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: Conrod kits ?

Postby Bevel bob » Mon Jul 30, 2018 2:09 pm

Its not a daft question,but the answer is complicated. You would need a re -design of the motor with a high pressure system and seals,an oil filter ,better piston rings, better head drainage, altered cam lubrication ,room for a bigger pump, a pressure release system etc. Was done on the last of the big bevels .

Scottish888
Posts: 27
Joined: Wed Feb 07, 2018 1:47 am
Location: Scotland

Re: Conrod kits ?

Postby Scottish888 » Mon Jul 30, 2018 3:29 pm

Damn! didn't realise the difference in engineering.
I have a 1981 bonneville so was just thinking about that but obviously totally different engineering.
All those conrod types out there and no two the same.

double diamond
Posts: 390
Joined: Thu Apr 28, 2011 1:20 am

Re: Conrod kits ?

Postby double diamond » Mon Jul 30, 2018 6:19 pm

Re: Mazzuccelli rod set. I have a few factory Ducati big end pins for NC 250 that measure ~27.3mm. Also have a set of flywheels with big end bore ~27.3mm. The flywheel big end bore was obviously rough cut too big for 27mm (a small portion of the rough cut is still left) so the flywheels were finish bored to 27.3mm and the oversize pin installed to save the flywheels. Since Ducati didn’t even list the rod set in parts catalogs, let alone individual pin/bearing/thrust washers, I’ve never seen any reference to these oversize pins. Perhaps the 27.3mm Mazzuccelli pin Eldert encountered was an oversize set by design rather than poor quality control. This pin might be for one of the rare 27.3mm flywheel sets. Also, if the press fit in a set of flywheels became too loose, the big end bore could be resized to 27.3mm (not a simple operation) and save the flywheels.

On the Guzzino website there are some NOS Mercur rod sets listed. The box says “Ducati 250cc” but the big end pin is shorter in length (58mm) than a NC 250. The NC flywheels are wider on the timing side so the pin is wider on one side as well. The rod set depicted in the Guzzino listing is the same width on both sides where it presses into the flywheel. I suspect this isn’t a 250 rod set. It looks more like an early 200 or maybe 175 rod. Might be worth an inquiry with Paul at Guzzino to get detailed dimensions.

Matt

ducwiz
Posts: 266
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: Conrod kits ?

Postby ducwiz » Tue Jul 31, 2018 9:29 pm


LaceyDucati
Posts: 242
Joined: Sun Sep 19, 2010 10:30 pm

Re: Conrod kits ?

Postby LaceyDucati » Tue Jul 31, 2018 10:21 pm

Yes these have already been discussed and are the same as the ones you have already shared a link from Ducati Classics. As I already mentioned, if you have anything other than a late 32mm crank you will need to machine 2mm from each thrust face to fit. They don't make a big mention of this, which has caught a few out.

Nigel

LaceyDucati
Posts: 242
Joined: Sun Sep 19, 2010 10:30 pm

Re: Conrod kits ?

Postby LaceyDucati » Tue Jul 31, 2018 10:24 pm

I stand corrected they have altered the listing to mention this now.

Scottish888
Posts: 27
Joined: Wed Feb 07, 2018 1:47 am
Location: Scotland

Re: Conrod kits ?

Postby Scottish888 » Wed Aug 01, 2018 9:08 am

How difficult would it be to source roller bearings of the correct original Ducati width allowing the conrod to be machined instead?
Does the small end also need machined or is that the same as Ducati original?
I guess original Ducati sizes were 18mm width for big and small end?, wider should make a longer lasting bearing I think but if you machine the crank maybe you should need to buy 2 conrods in case production ceased? Or would you be able to shim a machined crank if you could only source 18mm conrods?
I would rather have a big end engineered to last as long as possible, is wider is "stronger"? or has it proven not to matter (for 250's at least)

Eldert
Posts: 561
Joined: Sun Nov 01, 2009 3:23 pm
Location: Hazerswoude Rijndijk Netherlands

Re: Conrod kits ?

Postby Eldert » Wed Aug 01, 2018 9:57 am

your bike is a very late type . you could have a crankshaft with a 32 mm bigendpin

then the kit would be a straight fit .

so what diameter is your pin 30 or 32 mm ?

Eldert

Scottish888
Posts: 27
Joined: Wed Feb 07, 2018 1:47 am
Location: Scotland

Re: Conrod kits ?

Postby Scottish888 » Wed Aug 01, 2018 12:22 pm

Hi Eldert,

I have not removed the crankshaft yet, I only took off the head and cylinder to have a quick look as why little compression and check the big end...it had play so I re-asembled all as I did not want to lose any parts in my garage which has too much stuff and not enough room.
Can the crankpin diameter be measured in situ?
After I tidy my garage I will strip the crank out and hopefully it will be the larger size :)
Can you tell me what are the special tools I must have to strip the motor, I have a good tool set but no special Ducati tools

Regards,

Alex

Eldert
Posts: 561
Joined: Sun Nov 01, 2009 3:23 pm
Location: Hazerswoude Rijndijk Netherlands

Re: Conrod kits ?

Postby Eldert » Wed Aug 01, 2018 2:45 pm

Hi Alex

you cannot measure the pin but you could look how wide the rods bigend is . 18 mm for the 27 and 30 mm pin
or 22 mm wide for the 32 mm pin

good luck Eldert


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