MV750 Soviet Flathead Rebuild

You poor, poor sucker. Hopefully your relatives won't have you also judged mentally incompetent.



Fortunately, you don't have the uglyass turnsignals to deal with.

I thought the Soviets were licensed to build the R71 (MV750) back when they were allied with the Germans, who already had moved on to the R75 by then.

Nicht Wahr?

You hear it both ways -
1) Germans licensed the R71 to the Soviets during the non-aggression act (Germans had moved on to the R75)
2) Soviets bought them and transported them home via Switzerland.

This machine is known as the M72 - plunger frame. I have one of those as well... civi-version

Nice lookin machine! How does she run?
Yes, they know I am sick. I know I'm sick. Somehow that makes everything better

Doesn't run bad.... but it will run even better when I set the valves properly (PO had zero lash on the right side, no wonder that side didn't run as strong)

Plus, I'm gonna apply some special 'speed' techniques gleaned from racing karts with 5hp Briggs flathead engines. They're essentially 'blueprinting' or machining to modern standards. I took the heads off, and this machine hasn't been rebuilt in a loooong time.

I'm planning on losing the ugly lights, but keeping the old rough primitive worn paint.

You have a very sweet looking machine with all the 'patina' Plus, the flatheads are just soooo much more better looking than the OHV engines.

Thanks for sharing your MV750, RomaDakota! Looks like a fine old machine. I'm looking forward to more details and photos. One doesn't get to see a machine like this one very often and not in this detail. Nice to get a look at the factory stampings, close up of the spark retard, etc. Have you figured out what year it is?

Compression checked, timing set, carbs roughly set. New plug wires, fuel hoses and fresh oil in the sump. The electrical system in bad shape, the wiring harness had seen better days. Not only that, it seems the PO went a little creative once he was faced with replacing the switch in the headlight bucket, lamp toggle switches.

Inside the headlight bucket was a mess including house-grade wiring and even connections done with wire nuts! I knew a harness would be in the future. But hey I am ready to hear this flattie run! Off to the local “batteries out the ass” store to fetch a 6V battery – not as hard as I expected. Placed new battery on the charger and I wired around things to get power to the coil.
Now we have a weekly guy-get-together where the guys hang out and wrench on their junk, drink beer and tell lies; you know it helps get everyone through the week and occasionally something actually gets fixed.

I timed the battery so it would be charged and ready to go for hangout time. A few wiring changes and few Balticas for the occasion… and I am ready to kick her to life!
Fuel on, carbs tickled and a couple of kicks with power off to pull in some mixture. Power on (jumper wire), throttle cracked… One kick, two kicks – boom, it fires! Now this caught me a bit off guard as I was not expecting it to come to life so easily. Third kick and she fires right up and catches! Smoke starts to puff outta the mufflers as I had put some oil in the cylinders ahead of time. Not running perfectly but on both cylinders! I let it run a bit before shutting it down. A cold beer and cheers all around pay homage to the moment.
After the beer, time to start again and dial in the carbs and monitor head temps etc. Starts on first kick – great sign! Still poppin smoke and running a bit rough. Some adjustments to the idle stop screws calms the idle speed. Some playing around with the cables get the off-idle response fairly compliant. But something just doesn’t sound right; kinda like a ringing sound coming from the upper portion of the gear tower. Common on the horizontally opposed Soviet bikes, the generator (or alternator) is gear driven off the cam gear. So from bottom to top you have the crank gear, cam gear then the genny gear. Having the gear lash too loose on the genny can make the gears quite noisey. So I loosen the generator and start the engine again.

Rotate the genny in one direction will increase the lash and the other direction with decrease the lash. Having done this a few times, I have a feel for it and the noises will change accordingly. The lash does change audibly as it should however the ringing remains. Dang, what is that? To eliminate gear noises, I remove the generator and start it again. Ringing remains, I kill the engine. Then I kick it over slowly with power off – you can hear a rattle from the gear tower. I have a thought. I probe the gear tower from the hole left by my removed generator. Yep, the timed breather is loose. The front engine cover must come off. Time for another beer.

Oh garsh.. you're giving me flashbacks- I worked on my Communist rats nest inside my headlight today... it was just a bit fubar. Not bad, just wrong. As in no headlight- ever. Not that a headlight makes much difference on these bikes.

My hi/low beam switch is junk as well- I've thought about the toggle switch. What are your thoughts? (Besides 'time for another beer') Your thread could come in handy!

Great thread so far- I'll follow closely. BTW, am I allowed to intrude on your thread in this manner, or is it bad form? Do I need to get my own Old Red POS Bike thread?

You're gonna need a really thick,soft gasket for that carb flange...

No worries - the more the merrier in this thread. I know us Soviet junk lovin' types tend to stick to ourselves.
On the light - I have two lame suggestions
1) Wire the bright on all the time - hey it is a 6V bright and should almost be enough light to drive 40 kph once dark.
2) Get the real switch. Not really that expensive and the bright/dim cable control is just f'in cool!

Thanks Tom! My first thought on your sighting would have been a Chinese CJ until you mention the 2WD. That shifts it to a MT16 Dnepr or modern Ural. The civi-version of the MV was the K750 (flathead with swingarm) but it wouldn't have a badge nor 2wd. So the mystery remains.

Ha - that was actually off my M72; some dork over tightened that poor carbie :eek1

Where was I?? Oh just a few screws before this…

Yep, that is what you get for buying a bike unseen. You know... I was riding along today thinking about this very thing. All bikes I own were bought sight unseen – SICK.

Anyway, here is a shot of the gear tower I mentioned in the last entry. The timed breather is dangling on the front of the cam. This is a shot of a different engine. Kinda crappy photo.

Here is a vid of the actual inside front cover with the breather sitting in it’s cavity. You will notice a hole that corresponds to an alignment pin on the cam gear. You can see the hole is a bit elongated. And…
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The positive.. the rattle-noise has been firmly located. The pin/elongated hole is fairly easy to fix by drilling out round and using a gauge drill bit that with some chilling in the freezer and tapping will be secured in the gear and matching the same size in the breather. The movement in the front case is another issue altogether. I had another lying around, so I swapped front cases. Maybe later, I will look into possibly machining it out and inserting a bronze bushing or something. Shame to bin it as it is original with a possible date of manufacture.


MeRide &#8211; generally, it is impossible to determine DOM for a Soviet bike. I have several and there are methods people use, however this is the first time I have seen any evidence I feel is concrete.

During the fix, more orange RTV noted, missing safety wire and a missing fold-over washer on the crank gear. This is a snap after I remedied these issues.

All of this is a-making me nervous; voices in my head saying you are going to have to take this entire thing apart. I try to ignore and carry on&#8230;

Oh yes, many of your ideas will be expropriated for the Good of the Commune of Ridership! Your pictures will be very handy, as I've not had mine torn down as far... yet.

I think my switch is ok, but the cable is kinda frazzled / nonfunctional. I thought of both your suggestions, it is possible we suffer from the same mental deficiencies. Actually, to one up you, I thought maybe I should wire together both the low and high. Its not like this thing will blind anyone. Of course, draining the battery / nuking the gen is a consideration.

Maybe one of those old GM floor mounted dimmer switches, held to the left cylinder head with baler wire would be appropriate.......

I took my fuel tank to my local radiator shop- it has some seepage issues and leaks on the air cleaner. Don't need anything bursting into flames.

This is my first trip into a Russian bike. I'm really enjoying it. More please.

no kidding. this thread makes me yearn for a soviet sidecar rig.

I felt accomplished after determining the rattling noise and being able to properly clean up the PO issues in the gear tower. However not seeing a fold-over washer on the crank gear, no safety wire on the bearing cage and more RTV, the seed was being cultivated.
The stud for the points box was bent and the threads were actually stripped. Small stud, so I knew I would have to order correct helicoil, tap etc; McMaster order placed. Once the items arrived, I repaired the threads. I buttoned up the front and started the bike – yes, the rattle is gone! Time to move onto the drivetrain. Drained the tranny, final drive and reduction drive on the sidecar, inspected fluids and refilled. 20 minutes after filling the tranny, there was a large pool of gear oil under the tranny slightly to the right. After looking it over it was obvious the reverse selector lever was leaking. There is a small o-ring that goes around the lever shaft. A small o-ring, no biggie, right? Huh-hum, the tranny has to come out and opened up to replace the o-ring…
At this point, it is just as easy to yank the engine/tranny combo. F-it! Gotta happen.
Here is the tranny yanked and on the bench. Sorry for the crappy photos; I was not expecting to show them to anyone except my hangout buddies.

Interesting about these trannys (KMZ factory only) besides having reverse is what is sometimes referred to as “Dneprglide”. The blue arrow points to a shaft that is actuated when the shifter selector is moved gear to gear. The shaft pushes against the clutch arm and actually disengages the clutch – Yes, one can change gears without using the hand clutch lever! This works best shifting up with the heal shifter.
The red arrow marks the reverse lever shaft that must be removed to replace the o-ring. Time to crack open the case. The PO had been in here as well evident by more orange RTV.


All looks well inside. Pulled the small pin and back out the shaft (red arrow). O-ring replaced and tranny closed back up.
Then it hits me… I need to open up A-N-Y-T-H-I-N-G with orange RTV evidence. No one who knew what they were doing would open up a Dnepr tranny and not take 5 minutes to replace a small o-ring that can only be replaced with the tranny opened up.
So in a fit with witnesses, I start taking the engine apart. My hunch was quick vindicated when I took out the first tappet - OHOHOHOHHHO!

Yep, that is the mating surface with the cam!! The remaining tappets looked the same. WOW. Who would put these back into an engine? Out with the bottom end.

For some needed therapy, I clean the case and take some time to inventory and put together a parts order.

Roma:

Where do you order parts for a rig like this? Is everything available?

Tom

Tom - amazingly you can still get parts out there mainly overseas. I takes some patience, digging, paying, waiting. Of course the older flatties (sidevalves) are more difficult than the OHV models. There are some parts that interchange. Bearings and many seals can he had in US - bearings are standard types like the crank front and rear are 207s. Etc.
Here are the good sources:
http://www.ural-zentrale.de/
http://www.oldtimergarage.eu/store/
Ebay is OK, but order quantity 2-3 to possibly get one good part. Sometimes it is a crap shoot. I have been collecting parts for 7 years or so, therefore I have many good spares.
I have made some good friends in Russia and time to time I ask them to assist.