Ural 650 crank small end bushing failure

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URALNUT60
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Ural 650 crank small end bushing failure

Post by URALNUT60 » Thu Mar 12, 2020 7:58 pm

Removed left side piston on 650 Ural crank left side rod big end bearing toast, when I pushed wrist pin out and removed piston small bushing came out in pieces, wrist pin didn't have any discoloration, some darkness on bushing pieces, anybody ever had problems with bushing?

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Snakeoil
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Re: Ural 650 crank small end bushing failure

Post by Snakeoil » Thu Mar 12, 2020 9:53 pm

That bushing is not the big end, it is the small end. Never saw or heard of a bushing crumbling. May be a blessing if wrist pin is okay. Measure bore to see if round and in spec. If good, press in new bushing, fit to pin if necessary, and run it.
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Rob
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Re: Ural 650 crank small end bushing failure

Post by URALNUT60 » Fri Mar 13, 2020 4:06 am

My bad Snakeoil meant to say big end bearing is tight on journal no side play when I removed piston small end bushing came out in pieces, was just wondering if before I install new crank if I should replace small end bushing with better quality product, didn't know if there was known problem with these or not! Thank you

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Re: Ural 650 crank small end bushing failure

Post by Tomcatfixer » Fri Mar 13, 2020 6:11 am

That's a new one to me, but I'm with Rob: if the crankshaft is still good, I would just press in a new bushing and carry on.

Since I've never replaced one, a question I have is: do they come with the (presumably) oil holes pre-drilled and, if so, do you just carefully align them with the holes on the rod little end before pressing or do the bushings come without holes and you're required to drill the holes after the bushing is installed, using the existing little end holes as a guide?
- Chad

Gordonsville, Virginia, USA

Current rides:
2015 Ural cT "Mobile Chernobyl", 2001 Ural Patrol "Little Red Bear", 1999 Ural Tourist "The RPOC", Mid-Nineties Ural Tourist "The Heap", 1994 Honda VFR750F

Previous rides:
2007 Honda VTR1000 FireStorm (Super Hawk in U.S.)
2001 Buell Blast! - - - - - - - 2005 Yamaha FJR1300
1993 Honda CBR600F2 - -1984 Yamaha FJ1100
Two different 1986 Yamaha FZX700S Fazers

URALNUT60
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Re: Ural 650 crank small end bushing failure

Post by URALNUT60 » Fri Mar 13, 2020 6:54 am

Crank is toast, left side rod real tight on journal and no side play, Have new crank just wanted to know if there was bad history on small end bushings, or maybe rod seizing caused this, I will chalk it up to isolated incident, have new crank ready to go

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Re: Ural 650 crank small end bushing failure

Post by Snakeoil » Fri Mar 13, 2020 7:27 pm

I'm curious, where did you get your crank? I think I bought the last NOS 650 crank from Terry Crawford when I did mine 5 years ago. Although, he did buy that huge lot of parts since then and might have found a few cranks in there.

Inspect your crank closely before you install it. I found huge machining chips stuck on one of the slingers. I also found a lot of crud. My guess was that Ivan Jr. dropped the crank into the degreasing tub and it went to the bottom and scooped up all the crud that has been accumulating since Khrushchev was in office. I put the crank in a clean plastic basin and flushed it with mineral spirits and was amazed at what came out. I suspect this lack of detail on those old engines is what led to so many early big end failures.

I'd also put the crank on centers and make sure it was straight. Better to find out it is tweaked now then 4000 miles down the road.

My 650 is electric motor smooth with the new crank. My best compliment was by buddy Jake said it ran quieter than his GS BMW. And Jake has put 100's of thougsands of miles on more than one bike in his 81 years.
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Rob
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Re: Ural 650 crank small end bushing failure

Post by URALNUT60 » Sat Mar 14, 2020 4:54 am

Thanks for the input

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Claus
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Re: Ural 650 crank small end bushing failure

Post by Claus » Sun Mar 15, 2020 9:34 am

Bad small ends are very common on 650 engines. The bore is very often oval and taper and the surface is far from being smooth enough.
What I do suggest is: ream the bore until it's cylindric and make a new bushing from bearing bronze (that would be RG 7 in german terms)The bushing should be with an outside diameter that is 1 or 2 /1000mm per mm diameter larger than the inner diameter of the small end. If you go to shovel head specs you don't go wrong. Press it in, ream it to between 1/100 to 2/100 mm play , drill the oil feeding holes and check for good function after appr 5 to 7 k km.
After reaming to cylindric shape in most of the times there will be no bushing available from any dealer.
I have experienced very often that just pressing in an available new bushing without bringing the small end to cylindrical shape will caus pre mature waer within 3 to 7 k km.
owned bikes: 93 Ural rig domestic model, 95 Suzuki DR 650 RSE, BMW R100GS, Suzuki GSX1100G rig, BMW R100R rig with Ural sidecar, Ural rig with BMW drivetrain under construction,

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Re: Ural 650 crank small end bushing failure

Post by URALNUT60 » Sun Mar 15, 2020 10:32 am

Thank you Claus

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