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Old 03-05-2012, 05:46 PM   #31
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Back to work..

When I unscrewed the transmission drainplug about a pint of clear water poured out, followed by a stream of watery baby poo. Thankfully I missed a photo of that treat, but this sidecover shot gives you the gist.



I figured now it would all have to come apart for inspection and a good cleaning inside and out, so I started disassembling and bagging up the parts and fasteners.



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Old 03-05-2012, 05:49 PM   #32
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Schweet!

Just add PINESOL !
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Old 03-07-2012, 06:06 PM   #33
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With the valve covers off I could see the valves and the cylinder bores. Both bores had pitting where water had sat at the bottom. It was hard to feel by hand, but some WD sprayed in there puddled up where the damage was worst.



Not too much carbon buildup. Supposedly this thing was rebuilt in Lithuania. It didn't look like it had too many hours on the motor. Too bad it sat out in the weather.




The motor turned but sounded pretty raspy. Time to get it out of the frame and on the bench for surgery.
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Old 03-07-2012, 07:19 PM   #34
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I got the motor heaved up on the bench. It's a ball-breaker. Got the distributor off and the timing cover off. Underneath the cover are the crank and cam timing geras. When the whole motor is turning it's like a big clock.



The cam shaft goes through the larger gear and out through the timing cover through the rear of the distributor points case. The end of the cam shaft has two lobes that open and close the points and provide the ignition.





On the other end the clutch looked a little worse for wear. Heavy rust particles and black sludge at the bottom of the bell housing.



The outer clutch plate screws were punched all around the edges. Some had been punched three and four times. Whoever put it together really really made sure they wouldnt back out. I ground around the edges of each with a Dremel, but even with an impact driver it took about 15 minutes per screw. My last driver tip broke on the last screw, but I was able to get it out finally.





I was all set with some longer bolts and some nuts I was going to use to relieve the pressure of the springs behind the clutch pack, but they were so cashed that there was hardly any tension left. I could keep the plates pushed in with one hand while I undid the last screw, and they all just fell out at the end..



Not pretty. the friction plate material looked like it was swollen from all the water in the housing.



I was almost afraid to delve further in.
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Old 03-08-2012, 04:01 AM   #35
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Wow, that's the worst clutch I've ever seen. :P

Don't stop now! Even though I still have my doubts regarding the worthwhileness of fixing that engine, I find this thread very interesting and wait for each new set of pictures with bated breath. ;P

I'm not one to talk, though. I spent $1000 on a thrashed out hack for a $450 motorcycle that I still need like $200 worth of parts for. >_>

Those timing gears look pretty good to me, and I bet the valves are salvageable. Is there anywhere to get oversized pistons for those things, if you have to bore it, without paying a million bucks?
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Old 03-08-2012, 04:39 AM   #36
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Quote:
Originally Posted by Leaf View Post
Wow, that's the worst clutch I've ever seen. :P

Don't stop now! Even though I still have my doubts regarding the worthwhileness of fixing that engine, I find this thread very interesting and wait for each new set of pictures with bated breath. ;P

I'm not one to talk, though. I spent $1000 on a thrashed out hack for a $450 motorcycle that I still need like $200 worth of parts for. >_>

Those timing gears look pretty good to me, and I bet the valves are salvageable. Is there anywhere to get oversized pistons for those things, if you have to bore it, without paying a million bucks?
Can't stop!
I already resolved the piston question. That will be revealed in a future post. I'm trying to do this on the cheap too, so I'm keeping a tally. I'll post that up at the end just for information's sake.

I appreciate any thoughts, though- thanks for replying. Like I said, this is my first time this deep into the bowels of a motor, and I'm really winging it. Better to learn on this thing than something like a Ducati, right?
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Old 03-08-2012, 05:44 AM   #37
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Quote:
Originally Posted by MotoJ View Post
Can't stop!
I already resolved the piston question. That will be revealed in a future post. I'm trying to do this on the cheap too, so I'm keeping a tally. I'll post that up at the end just for information's sake.

I appreciate any thoughts, though- thanks for replying. Like I said, this is my first time this deep into the bowels of a motor, and I'm really winging it. Better to learn on this thing than something like a Ducati, right?
Thats the way to do it Id say! I havent jumped into a project like that either but if I did I figure this is the type of engine to start with..

Great thread man
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Old 03-08-2012, 09:49 AM   #38
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Behind the clutch was a pretty massive flywheel, also rusted. The clutch springs sit in the six recesses in the flywheel.

Besides the rust, it looked like someone threw a handful of sand in the case.



Behind the crank nut is a lock tab washer. I bent the folded part back with a cold chisel so I could get to the crank nut. Next I put a 36 mm socket on the crank nut, blocked the flywheel with my Stanley mini prybar, and gave the end of the longbar a whack with the BFH. That broke the nut loose and I spun it off by hand. The motor I clamped to the bench because trying to break the nut loose without it I was just lifting the motor.





So far, so good.
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Old 03-08-2012, 10:23 AM   #39
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You tease!!! Show us what is behind the flywheel! :P
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Old 03-08-2012, 10:35 AM   #40
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Great post! Thanks for keeping us teased till the next picture!
Funny...I should been put away from these flatheads just by looking at your pics....but I am more and more attracted...like a night butterfly to the light.... and its ultimate death!
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Old 03-08-2012, 10:57 AM   #41
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wow. I am in. But, you wont get away with it that easy, How much did you pay?
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Old 03-08-2012, 11:21 AM   #42
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OK, I'm back...

The flywheel very thoughtfully has tapped holes in itself on either side of the center so a puller can be used to detach it from the crank. The big nut had it pressed on there pretty well.



Nice, huh? Look at the clutch carrier studs. A little grooved up. Couldn't have been too smooth a pull.



So, under the flywheel was yet another obstacle. This plate is the rear crank bearing carrier. Around the inside of the center there is supposed to be a felt ring that is the seal between the flywheel and the bearing. It was pretty much just some lint by the time I saw it. You can see a bit of safety wire there, too. Not a lot of Loctite used back then, or at least, not by the Lithuanian guy.



Plenty of rust, oil, sand, and PB Blaster to mop up...

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Old 03-08-2012, 11:47 AM   #43
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Ennn Soviet Russia, Clutch pull You!

Russian bikes don't need loctite. You just have to leave them out in the weather and a brown-colored Russian Loctite forms. ;3 Your bike has plenty! XD

I'm not poking fun at Russian bikes in particular. Mine use West Virginia Loctite, as well, which is the same formulation with a different brand name.
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Old 03-09-2012, 05:34 PM   #44
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I left the rear bearing carrier in for the time being and worked at getting the cylinders off. It took a little pulling, even with a good dose of spray lubricant.



You can see the tappets and valve adjustors.




Flat-top pistons with four rings. They were both a little bit scraped up. This is the left side. It looks like it was run without enough oil. The right was even worse.

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Old 03-09-2012, 10:03 PM   #45
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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.
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