crankcase wont split

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Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

crankcase wont split

Postby Scottish888 » Mon Apr 08, 2019 12:19 pm

Hi Folks,
Began to strip the engine of my 1974 Ducati 250 mark 3 so I can get the crank out for a big end replacement.
All went well until trying to split the crankcase, it just won't split.
Removed the 6 allen bolts and two hex bolts at the top, been tapping with a rubber mallet but it is not moving much.
I can get a 0.05 feeler blade all the way around but no amount of rubber hammer hits make it move anymore, was 4 hours yesterday trying to coax it, end result is 0.05mm gap. Any tips?
Also noticed the timing end of the crank where it sits in a bush has some scoring, how critical is that area and any solutions?
I could polish them out with varying grades of emery roll but are new bushes reamed to fit or just a standard diameter?...if they are available.
Stripped many bike engine mainly japanese and some british yet never encountered a crankcase that would not split, the puller idea is great for the clutch case but nothing in the crankcase.

Regards

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

Re: crankcase wont split

Postby Samurai » Mon Apr 08, 2019 12:36 pm

Had similar problems splitting my narrow case 175TS. In the end a combination of heat, oblique tapping around the joints, perseverance and WD40 eventually made them give up.

It was a right PITA though, but once you've started to to get even the slightest gap, things should start to get easier and at some point you should be able to get some of those plastic wedges used to level up window and door frames in to the gap.

You can then carefully and evenly use them to help get it wedged open, but at that point I found that they were starting to come apart anyway.

Patience and heat are your friends ;)

Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

Re: crankcase wont split

Postby Scottish888 » Mon Apr 08, 2019 1:08 pm

Thanks Samurai,

I applied lots of WD40 around the case joint but not enough to get any small plastic wedge in as a 0.05mm feeler just fits.
The oil pump on my bike engine has security wires through all the oil pump screws, is that standard?, the cases were beautifully clean and shiny inside, quite surprising.
b_edited.jpg
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Jordan
Posts: 1380
Joined: Fri Dec 24, 2010 11:29 am

Re: crankcase wont split

Postby Jordan » Mon Apr 08, 2019 1:14 pm

Rubber mallet absorbs too much energy. Try a heavy lead or copper one instead.
Timing side bush wear was mentioned mid-January. See thread, "350 crankshaft question".
Good news is that the low pressure oil system doesn't seem to mind if this bush is not in perfect nick.
Security wired screws for oil pump is standard.

Crankcase splitting tool.jpg

I've never needed or even seen one of these tools, but I guess it could be made up if needed.
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Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

Re: crankcase wont split

Postby Scottish888 » Mon Apr 08, 2019 1:59 pm

Thanks Jordan,
The rubber mallet did not seem to be effective but I was too worried to use std hammer, will get a copper head hammer, still worried about damaging these cases though.
The case splitter pic would be an interesting last resort.
Thanks for the info on the bush.

Regards

ducwiz
Posts: 604
Joined: Tue May 22, 2012 12:52 pm
Location: near Frankfurt, Germany

Re: crankcase wont split

Postby ducwiz » Mon Apr 08, 2019 5:14 pm

Code: Select all

Removed the 6 allen bolts and two hex bolts at the top, ...


Have you also removed

- the left crankshaft nut, the primary pinion and the alternator rotor
- the right crankshaft nut and the bevel gear on the crankshaft end
- the clutch's center nut and the entire clutch assy
- the chain sprocket together with it's nut

If all this was done, at least one of the three shafts inside seems to be stuck in either of it's ball bearings. Try to find out which shaft it is, and on which side it is obstructed. A copper hammer then might help. Or a kind of pressing tool has to be constructed from a steel bar and pressing spindle or screw.

?? Hans

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

Re: crankcase wont split

Postby ranton_rambler » Mon Apr 08, 2019 6:35 pm

I didn’t enjoy splitting my cases at all, never mind the further several times to set the shimming! First time was hardest, and I used a block of hardwood and a normal steel hammer.
Ian

Bevel bob
Posts: 1043
Joined: Thu Apr 15, 2010 8:01 am
Location: Bromley Kent UK.

Re: crankcase wont split

Postby Bevel bob » Mon Apr 08, 2019 7:04 pm

I once watched Vic Camps mechanic strip a motor at a race meeting. He worked really fast in order to split the cases while the motor was still hot from running. Put it in an oven.

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

Re: crankcase wont split

Postby double diamond » Mon Apr 08, 2019 8:21 pm

All the shafts should be a slip fit in their respective bearings. But the dowel pins can be very tight. If you can fabricate a drift that is exactly the I.d. Of the three bolt holes where the dowels are located, you can split the cases by knocking the dowels out. Dowels are located front and rear of the cylinder and the lower rear engine mount bolt.

Matt

LaceyDucati
Posts: 521
Joined: Sun Sep 19, 2010 10:30 pm
Location: Wales UK
Contact:

Re: crankcase wont split

Postby LaceyDucati » Mon Apr 08, 2019 8:28 pm

Use a hard plastic faced mallet and alternate between the front filler neck and breather, but keep the taps "moderate". The casing will be stuck on the dowels, so another trick is to place a bar (alloy/brass/nylon) in the selector drum and give that a sharp crack with a steel hammer. The drum is next to the rear dowel so will exert force close to the dowel. the case is thick around the small end of the selector drum so it will take it okay. I've never had to resort to a case puller or wedges (plastic should be okay, but still not keen) and never had a set of cases that didn't respond to these methods or had any "collateral" damage either. This is assuming all engine nuts etc have been removed. Don't be to worried about the scoring, they are all like that to some extent. A light polish in a lathe would be fine.

Nigel


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