Motoscrubs.com

Hi, glad to be a new member. My question is about my '70 350 scrambler which I bought new. I have the cases split (rod knock put her out of commission many years ago) and am finally getting around to a restoration. I took the crank to a local machine shop which specializes in motorcycle work and asked them to split it for me, but they gave it back saying they were afraid of breaking it after putting a huge amount of pressure on it without success. Anyone have any ideas where to go with it? Uneasy about doing it myself as I have no experience with this.
THANKS

If in the UK, send it to Nigel Lacey. If not, hopefully someone else can advise.

Ian

it is a stepped bigendpin . so you cant push the pin out from one side thru the other .
you have to support one cheek and press the cheeks apart.

Eldert

Ducati crankshafts are not difficult to disassemble but do require some specialized knowledge and tools. If your machine shop does not possess these, I can understand their consternation.

What corner of the world are you posting from?

Matt

Also ...

Getting it apart is the easy bit . You've then got to put it together again .

As Ian: give it to a specialist - Nigel ideally, if you're in the UK (hint: please add your location to your personal profile )

Ciao

Craig

Thanks much for the advice, everyone! I am in the Northeastern US, so a little out of the way for UK. I wonder if shipping to Nigel is a possibility. I'll continue to search around here, and let you all know what I find.

Nigel would no doubt do a great job, but that's a heck of a distance to send a heavy item.
You need an hydraulic press, and some tooling that can be made up by a welding shop.
Alpha Bearings in UK gave away a booklet on crankshaft reconditioning methods, of which I have a copy.
It describes the tooling in enough detail.
If interested, I'll send you a pdf.

On the east coast, there's Falicon and Syd's Cycles who have experience with Ducati single crankshafts but they're both in Florida. There must be someplace in the Northeast but nothing comes immediately to mind.

Matt

Please let me know if I'm wrong, but I don't think there's anything unique about the crankshaft, to the extent that you need to find a Ducati specialist to work on it.

I agree that, to a certain extent, a pressed up crankshaft is a pressed up crankshaft. However, there is a distinction between two stroke cranks (which is what most shops who accept presswork will be dealing with) and four stroke crankshafts. Two strokes are typically solid, straight big end pins. Line up the flywheels, press the pin in with no regard to orientation, set rod side clearance, true and you’re done. Four strokes require that the oil passages in the pin are aligned with the oil passages in the flywheels. With stepped big end pins, there is no need to set side clearance providing the parts are properly dimensioned, but still needs to be checked. In the case of widecase crankshafts, the flywheels are different diameters, so aligning the flywheels requires some sort of approach to get the pinions in the same plane (unless you have a jig like Rick devised: viewtopic.php?f=3&t=2210&p=16800&hilit=rick#p16800).

Also need to know that the sludge trap should be cleaned out (and how to remove the plug without damaging the threads in the flywheel) , installing welch plugs in the big end pin, inspecting the big end pin ID for sludge deposits (providing you’re dealing with an OE type pin), removing the drive side set screw to clean the oil passage. Pressing the crankshaft apart requires placing shims next to the rod to take up the gap between the support plate and the flywheel, which will become apparent once pressure is applied. You also want a support plate that is as thick as possible since, as DHW has observed, it takes a good deal of pressure on the big end pin to get it to move. Thin support plates that work fine with two strokes will bend before the Ducati pin lets go. Not to say that a reasonably competent individual who has experience with pressed up crankshafts can’t figure these out, but apparently the place DHW took his crankshaft didn’t want to acquire the skills. Someone who has previous experience with Ducati crankshafts will at least know what he’s dealing with.

Matt