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Old 03-10-2012, 05:21 PM   #46
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Have a look at http://bcozz.multiply.com/journal/it..._Jiang_project for some modifications and improvements suitable for the M-72.
Thanks- that's a great thread. I actually stumbled across it myself. I've been thinking about using his air cleaner mod..
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Old 03-14-2012, 05:44 PM   #47
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How's the rebuild going? *nudge nudge nag nag* >_>
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Old 03-15-2012, 06:12 AM   #48
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How's the rebuild going? *nudge nudge nag nag* >_>
Still plugging away. I've been having problems with Photobucket- it quits right in the middle of trying to upload a photo. PB sucks out loud!
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Old 03-15-2012, 06:16 AM   #49
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<<>>

Jim, SMUGMUG!

<<>>
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Old 03-15-2012, 07:05 AM   #50
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I use imgur, meself, though it's not really right for an ongoing photo collection, I reckon.
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Old 03-15-2012, 07:17 AM   #51
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<<>>

Jim, SMUGMUG!

<<>>
Yeah, I've thought of that, but I'm kind of screwed now- I haven't figured out how to transfer my pics in a block, rather than one by one. It would take forever.....
Also, it would compromise the posts I've already put up, unless I leave just those pics in PB. Just a lot of time either way...

Has anyone else had this problem with PB? Is it their crappy servers or is my connection too slow?
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Old 03-15-2012, 08:14 AM   #52
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Badda-bing!

Another crisis narrowly averted... switched to Firefox and everything seems to be running smoothly. I WILL be switching to SmugMug, however. The aesthetics are 100% better just to begin with- PB looks like it was put together by a first year web designer compared to SmugMug. Anyway, back to the motobike:

The cylinders pulled off with a whumpff, so they still had pretty good ring-seal, despite the pitting in the bores. They are dissimilar in that one side allows oil into the bore through just by oil being slung around in the case, while the other cylinder bore is lubricated through three drilled oil holes. This has to do with the way the crank rotates, evidently.






The Soviets were pretty fast and loose with the machining- look at the chatter marks in this bore:

I read somewhere that the motors were "cold-broke" in- they were towed in gear behind a tractor to get all the badly machined parts moving together. Also that they were sometimes first filled and shipped with fish oil in the cases!

With the cylinders off I removed the pistons. Each is held on the conrods with wire-type circlips that look like they was hammered and rolled by a blacksmith. The wristpins were pretty tight- I knocked them through with a hardwood dowel.



Can anyone read these wristpin markings?


Note the four sets of rings- still the sides are scuffed-up! The clearance must be pretty loose until they swell up and stop slapping. I read they were mostly made out of whatever mostly aluminum scrap was lying around- old planes, pots and pans, hubcaps, auto trim, etc. Lots of impurities.
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Old 03-15-2012, 08:45 AM   #53
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So, pistons out. On the inside of the piston I found these initials cast:



Looks like KMZ to me. That's the Kiev factory in the Ukraine. Bikes made there were eventually referred to as Dneprs, while the bikes from the Irbit factory- IMZ in Siberia, were to be called Urals. Earlier I posted a pic of a case stamp I think means IMZ. Someone likely put this motor together with parts from both manufacturers- whatever was lying around!

Next the crank timing gear. This one took some muscle. I also used a heat gun and "Freeze-it". It came off finally with a loud enough pop that I was sure something had broken. I destroyed one cheapo gear puller. The second one I had to grind down the hooks to fit behind the gear.

First there's a bent over lock-washer and a bolt to remove.




This Fisher Price puller didn't make the cut..


Yay Harbor Freight! (I'm ashamed to admit that)



Finally the little bugger was next to his big brother Cam-gear.



Behind is the front crank bearing carrier. The bolts are supposed to be safety wired, but weren't.



That little macaroni tube on the left side of the bearing carrier is the oiler for the gear and the bearing behind.
Look at the oil passage holes top right and bottom left in the case. The casting is so rough it would cut your fingers. I might give those a file later. Can't hurt.
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Old 03-15-2012, 08:58 AM   #54
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Sorry for the gigundo photos- I'll get better at this new setup eventually.....

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Old 03-15-2012, 10:12 AM   #55
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Next the tappets/cam followers/push-rods thingamabobs came out. These follow the lobes on the cam and operate the valves.


They're held in place by a tapered keeper and 10mm nut. After that was undone they pulled out by hand slick as snot.





With those out the last things left in the case are the oil pump and the crank.

The rear crank bearing lives behind this retainer that is behind the flywheel. There are nine bolts around the perimeter, all safety wired. It is thoughtfully tapped to use a puller.



Note my pristine basement workspace. Like a surgical theater!



Made in the USSR!



Another KMZ casting inside the bearing retainer.



Inside is revealed the rear crank bearing, a bearing cover/spacer, and the notorious "wavy washer" that so many Russian Iron enthusiasts are familiar with- just where the hell does it go exactly? In my bike it was right behind the flywheel, acting as the end-play reducer, I guess. It will go back in the same way.



At the left is the oil pump shaft. It is inserted in the bottom of a gear that is actuated by the camshaft. The camshaft turns the gear, turning the vertical pump shaft, which turns gears in the oil pump, which sucks oil out of the sump and through oil tubes that transverse the bottom of the case front to back, to vertical passages to front and rear bearings and destinations above.



The disc behind the bearing is one of two "oil slingers", one at each end of the crank, that help distribute oil in the case but which principally serve to collect debris in the oil. The manuals tell you to disassemble the motor every 30,000 km and scrape the goo out of the slingers, or else replace them. Along with this strainer around the oil pump in the sump, there is no other oil filtration. Makes you appreciate screw-on filters!





I gave up on those gloves after awhile, BTW. It was a nod to health consciousness.
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Old 03-15-2012, 10:31 AM   #56
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The Evil Empire fights back..

The absolute biggest PITA disassembling this heap was getting the oil pump gear cap out of the top of the case. Years of running heat had galled the steel cap in the aluminum case. I tried everything. I soaked it for days in PB Blaster, heated around the cap with a torch, put an ice pack on it, put a long bar on and beat it, you name it.

Finally at the local auto parts store I saw a can of "Freeze-Off". Basically WD-40 and compressed air. That's what did the trick. This is my official endorsement of Freeze-Off!




I was pushing and pulling so hard on the end of a long bar with a knurled handle, trying to get that cap busted loose, it bit me back..

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Old 03-15-2012, 11:08 AM   #57
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You haz some laydeez handz Jim.

On a serious note, what is the point of bending the one side of the washer? It isn't bent over the end of a bolt or anything to keep it in place. I've seen the internals of several Soviet bikes that had this done in various places in the engine.

Are you finding more KMZ cast parts than IMZ? How was the tolerance in the cylinders with the pistons in? Enough for a good amount of slap?

Looking good, eager to see how this turns out.

Oh. Where's you get a ratchet that big?
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Old 03-15-2012, 11:56 AM   #58
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You haz some laydeez handz Jim.

On a serious note, what is the point of bending the one side of the washer? It isn't bent over the end of a bolt or anything to keep it in place. I've seen the internals of several Soviet bikes that had this done in various places in the engine.

Are you finding more KMZ cast parts than IMZ? How was the tolerance in the cylinders with the pistons in? Enough for a good amount of slap?

Looking good, eager to see how this turns out.

Oh. Where's you get a ratchet that big?
  1. I know- girly-mon. that shot doesn't even show you the color of my nail polish..
  2. The bent lock washer is designed with two bendy parts. Where they are used, there is a hole in the surface the washer is applied to, under the bolt. The washer has a protruding tab that is bent 90 degrees and inserts into that hole. Then, once the bolt is tightened up, one side of the washer is bent up against one flat side of the bolt, usually opposite the side the tab is. In that way, the tab and bent part keep the bolt from unscrewing itself. If you scroll back up to one of the gigundo photos you'll see a closeup example...
  3. Hard to say what this bike is for sure. The Lithuanian paperwork/title says IMZ, but that doesn't really mean much- it just had to look official to get it through customs. I found that IMZ stamp on the case, but that's the only place so far. Besides the pistons and bearing carrier, folks have told me the valve covers, mufflers, and tank (or at least the pads) are KMZ as well, from a K750. I've found a couple other stamps that I'll post pics of later on that aren't either IMZ or KMZ. I suspect when the previous owner went looking for a bike in Lithuania, the old gent who built this one put it together from whatever was on hand and gave it a quick paint-job.
  4. Thanks- me too!
  5. I don't have the experience to say what was causing the piston damage I saw. First guess is no oil, but otherwise, they were either too tight and starting to seize or they were slapping and getting scuffed up that way, or both. They measured about 78mm, which is the stock bore, I think. Actually there were a few measurements- I don't think either piston or bore were perfectly round, and the bore tapers towards the outside.
  6. That bar I got years ago at a huge flea-market on the outskirts of Baltimore. it was at an old drive-in and if you hunted around for a few weeks eventually you could outfit your whole garage- USA tools for a fraction the price of new. Haven't been there in a long time. I remember there were boxes and boxes of VHS porn too- that stall was always covered over with old dudes like crows on a run-over badger.
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Old 03-15-2012, 03:02 PM   #59
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I 'spect you don't want to see my pianist hands, then. >_>

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Yay Harbor Freight! (I'm ashamed to admit that)
Nuffin' wrong with Horrible Fright! I rock a bunch of HF junk for the tools that I don't use often enough to justify spending much on. :3

Heck with their power tools, though. :/ I burned up my Horrible Fright drill faster than my cats can lick their backsides. :<
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Old 03-16-2012, 08:12 PM   #60
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The birthing of a crank

Last bit of innards to come out was the crank. The front crank bearing stayed with the front bearing retainer. The rear bearing stayed on the crank. The conrods are pressed on the shaft in between the lobes, which means they can't be removed like on a BMW, and so the whole shebang has to come out the back end of the case. This turned out to be some kind of Chinese puzzle.


AARRGH!


WTF!!!

I had it turned and pulled this way and that and it was always a red C hair too big to make it out, either at the back or at the end of a conrod on one side or the other. I was ready to hurl the whole hunk onto the floor, but instead a took a deep breath and left it for the next day. The next morning I had a link from Roma Dakota in my Inbox to Mr. Bill Glaser's Ural page: http://myural.com/crank_removal.htm

Eureka! I went downstairs, set down my coffee, flipped the crank this way and that and it practically fell out the back end in my hand.



I thought this was analogous to holding a human sacrifice heart or something...

So, finally the case is empty. Crap, what have I done?!

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