Snapped crank shaft

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Korto
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Snapped crank shaft

Post by Korto » Wed Sep 11, 2019 8:54 am

Least, I assume it is. I got as far as removing the gearbox before I lost the light, but the clutch (which is, PS, screwed) is all wibbley-wobbley--the entire, bolted together unit, that is (didn't do the casing to the gearbox much good, either).

Got the previous issues sorted, organised to get an engineer's inspection next week, took it out for a test ride, and snapped the crank shaft. No idea what other damage has been done.

Anyway, what's the easiest way to inspect the inside of this piece of $#!+? Am I going to have to remove the engine from the frame? Can anyone tell me what I should be doing/look out for while I'm doing it?

I'm starting to wonder if the sidecar is too big and heavy for it. It was always a bit of a worry, but when it wasn't running, I couldn't test it. Now it is running, and this happens. It's a wide two-seater, weighs 130kg if I remember correctly.
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Snapped crank shaft

Post by gobium » Wed Sep 11, 2019 10:22 am

Dneprlover to bat phone

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Re: Snapped crank shaft

Post by jaybird » Wed Sep 11, 2019 12:59 pm

You may have broken the crank but it could also be that the flywheel retaining bolt loosened up, causing the flywheel to come loose from the taper allowing it to wobble.
Either way you need to start by removing the transmission and clutch.

Happy trails,
Jaybird
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Re: Snapped crank shaft

Post by Peter Pan » Wed Sep 11, 2019 2:06 pm

It is way easier and faster to take out engine together with transmission then only transmission. Last occasion together with Rick - "Medio Tico" 3 1/4 hour
Photo my Sophie in March together with Fran
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Sophie Travelair = Patrol 2013
8 weeks 12.000km Oregon-Alaska-Oregon
With a DIY foam air filter the rig runs well even in tropical rain = :moto:
Final drives: 1. at 5000km, 2. at 34.000km(+friction plates) 3. at 42.386km
transmission: 1. 40.000km. 2. installed
Engine: 1. 43.388km crank replacement: Back on the road since 23.Okt.2019 :party:

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Re: Snapped crank shaft

Post by dneprlover » Wed Sep 11, 2019 7:30 pm

Lugging engine scraps crankshaft. Mt9 sweetest of Dneprs and softly tuned. Do snap cranks but not very common. Engine out , gearbox off, clutch flywheel off. see what damage. take pix and post of internals

what country and where are you?

Oh, and it's not a Ural so don't call it a piece of sh** PLEASE
Neval BMW/MT11 800cc hybrid, Neval 2wd MT10-36, Neval standard MT10-36, Neval MT16, another MT11, BMW/MB650 hybrid , K750m , MB750 and a standard MT10-36 outfit + 2 large sheds full of spares for them.

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Re: Snapped crank shaft

Post by gobium » Wed Sep 11, 2019 7:52 pm

dneprlover wrote:
Wed Sep 11, 2019 7:30 pm
Lugging engine scraps crankshaft. Mt9 sweetest of Dneprs and softly tuned. Do snap cranks but not very common. Engine out , gearbox off, clutch flywheel off. see what damage. take pix and post of internals

what country and where are you?

Oh, and it's not a Ural so don't call it a piece of sh** PLEASE
Can he remove the rod arms with crankshaft still inside?

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Re: Snapped crank shaft

Post by dneprlover » Wed Sep 11, 2019 8:00 pm

gobium wrote:
Wed Sep 11, 2019 7:52 pm
dneprlover wrote:
Wed Sep 11, 2019 7:30 pm
Lugging engine scraps crankshaft. Mt9 sweetest of Dneprs and softly tuned. Do snap cranks but not very common. Engine out , gearbox off, clutch flywheel off. see what damage. take pix and post of internals

what country and where are you?

Oh, and it's not a Ural so don't call it a piece of sh** PLEASE
Can he remove the rod arms with crankshaft still inside?
Yes. big end shell bearings can be unbolted after removing cylinders. cramk comes out easy when timing gears off
Neval BMW/MT11 800cc hybrid, Neval 2wd MT10-36, Neval standard MT10-36, Neval MT16, another MT11, BMW/MB650 hybrid , K750m , MB750 and a standard MT10-36 outfit + 2 large sheds full of spares for them.

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Re: Snapped crank shaft

Post by Korto » Wed Sep 11, 2019 11:08 pm

jaybird wrote:
Wed Sep 11, 2019 12:59 pm
You may have broken the crank but it could also be that the flywheel retaining bolt loosened up, causing the flywheel to come loose from the taper allowing it to wobble.
Either way you need to start by removing the transmission and clutch.

Happy trails,
Jaybird
I would have really loved that to be the case. However...
Image

Image


The gearbox is already off. To be honest, while you're saying it's easier to remove the box and engine together than separately, I'm not sure if I would be able to handle the combined weight alone.
So I pull this engine out... all as one piece? Should I take the cylinders off first?
Got to figure out where I'll put the damned thing. And then whether I'll be able to get it there.

Australia, Newcastle. Maybe I should put that in my sig. I'll do that.

"Oh, and it's not a Ural so don't call it a piece of sh** PLEASE"
For a variety of reasons, only a few to do with this bike, I'm not in a happy place right now. Let's just say this hasn't been the best of years.
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Snapped crank shaft

Post by Lokiboy » Wed Sep 11, 2019 11:44 pm

92C76147-7994-47FF-A32E-14F75A39608E.jpeg
Dang! :lol:
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Re: Snapped crank shaft

Post by dneprlover » Thu Sep 12, 2019 11:27 am

See the problem. Never known it happen to a 9 but I've broken a few MT11 ones and seen a few others go. That could possibly be a later replacement. We can probably help with advice on here but I suggest you go on the Aussie section of Russianiron.com and try to get hold of Peter Williams for more local information. I think Aussie knowledge on here was banned.
Crank can be changed with cases still in frame if you wish to struggle with the timing chest area. I done it once but took forks and wheel off to give room coz I'm lazy

Pity you not in UK, I have a few good bottom ends somewhere at home and not a lot of use for them now.
Neval BMW/MT11 800cc hybrid, Neval 2wd MT10-36, Neval standard MT10-36, Neval MT16, another MT11, BMW/MB650 hybrid , K750m , MB750 and a standard MT10-36 outfit + 2 large sheds full of spares for them.

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Re: Snapped crank shaft

Post by Peter Pan » Thu Sep 12, 2019 1:52 pm

To take out the engine I took off the alternator and as you might see that we used a scissor jack for support. (tied the main stand for not flipping the whole bike) with 2 persons it was much easier to wiggle the engine out by pure muscle, then by using a hoist.
Leave cylinders put, there is a lot of space and you do not have to worry about damage to the studs.
Tilt the back a bit up, so the pan gets off the frame, and turn out the back towards left (kickstarter side), rest on frame, then the partner can come around and help to get the engine out on the work table.

You have done a bloody "full job" with your crank. Hat off, pal.
Sven
Sophie Travelair = Patrol 2013
8 weeks 12.000km Oregon-Alaska-Oregon
With a DIY foam air filter the rig runs well even in tropical rain = :moto:
Final drives: 1. at 5000km, 2. at 34.000km(+friction plates) 3. at 42.386km
transmission: 1. 40.000km. 2. installed
Engine: 1. 43.388km crank replacement: Back on the road since 23.Okt.2019 :party:

The Avatar are 2 rice grains stating life's essence:
"The most important you cannot see!"
=> Attitude makes the difference!

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Re: Snapped crank shaft

Post by Korto » Mon Sep 23, 2019 12:15 am

OK, so I've removed the engine. It turns out that the engine is light enough for one moderately fit and strong adult to carry any reasonable distance (with oil drained and gearbox already removed. No promises otherwise).

My method, for those wanting to know, was to support the weight of the engine with a jack underneath (with a wooden board as a spreader. There may otherwise be a risk of punching through the sump), but not jacking it up, just taking the load; then undo the bolts restraining the engine, and then jack the engine up high enough to clear the lower bar of the fame and lift out. It's relatively easy.
Image

After taking off the front cover, and the cylinders, I feel relatively confident that the only damage done has been to the crankshaft (and one clutch-plate. I mustn't forget that. I'll feel annoyed if I wait a month to get a new shaft, and then realise I forgot to order the plate).
I'm trying to figure out how to remove the shaft. I can see how to detach the con rods through the cylinder holes, that seems simple, but I'm looking at the gears here...
Image

My feeling is
1) Remove that smooth silver disk thing
2) Remove the bottom gear
3) Undo the bolts holding the plate the top gear shaft is in. Remove top gear and plate together.
4) Undo the bolts holding the plate the middle (crank shaft) and bottom gear shaft is in. Remove plate and see what comes with.

However
1) When I undo the bolt in the silver disk thing, the silver disk doesn't want to come off, even when lightly tapped with a mallet.
2) The bottom gear doesn't seem to want to come off either. Maybe it's a press-fit?
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Snapped crank shaft

Post by dneprlover » Mon Sep 23, 2019 3:35 am

silver disk is centrifuge oil cleaner. should be cleaned out at service. will come off with puller once bolt removed but might separate exposing crud chamber.. keep seals safe and will be ok. All gears will pull straight off when bolts removed but may be a tight fit
Neval BMW/MT11 800cc hybrid, Neval 2wd MT10-36, Neval standard MT10-36, Neval MT16, another MT11, BMW/MB650 hybrid , K750m , MB750 and a standard MT10-36 outfit + 2 large sheds full of spares for them.

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Re: Snapped crank shaft

Post by Korto » Tue Nov 05, 2019 9:41 pm

OK, so I've gotten my new crank shaft, installed it in, and then noticed while playing with it a HUGE amount of slop between the big ends and crank pins. So pulled it all out again (swearing), and measured things up (wouldn't it have been wonderful to have done that BEFORE putting it in in the first place, idiot?), and found that the crank pins on the new crank are about a millimetre smaller then big ends (that includes those inserts).

The sizes I've got on the pins (in millimetres) are below. While these measurements were done with calipers, not a micrometre, I did 3 on each and averaged, so it should be fairly accurate.
Front : 46.76
Rear : 46.72

Does anyone know what they're supposed to be?

My pistons measure at 47.98 and 47.84 front and rear.


What's my best plan here? Should I get new, thicker, inserts? Should I have the crankshaft rebuilt?
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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Re: Snapped crank shaft

Post by Korto » Wed Nov 06, 2019 7:41 pm

The guy who sold me the crankshaft was surprised by the undersizing, and the best theory he can come up with was that the Loyal Soviet Comrade Worker! had hit the vodka a bit hard that day.

I find this theory eminently believable. Comrade probably had quotas to fill.

His solution is to send me (free of charge, of course) 1.25mm thicker shells.

Assuming my measurements are correct, this would effectively make the pins 48.01mm and 47.97 mm. I'm concerned, because this is larger than I measured the piston big ends. But not a lot bigger. Assuming my measurements are correct.

I could send the crankshaft back and buy from another supplier, who has a crank with conrods already attached (and therefore presumably fit). The problem with this is not only the time wasted, but it would cost something like an extra $200 to $300, and my finances are screwed right now.

Incidentally, resizing (building up) the existing pins here would cost around $500, more or less (more if it's cast iron, less if it's steel).

I need advice here. What do I do is the shells are a fraction of a mm too large? Am I seeing problems where none exist, or is this a real issue and I should send it all back and try again?
Australia, Newcastle. 1972 Dnepr MT-9... mostly... I think...

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