Dneipr running at last BUT

Are ya having a problem with your rig? We'll try to help. Share your tech tips and experiences here. Dr. Billy Glaser, author of the "Unofficial 750 Ural Service Manual" site myural.com, is moderating this section.
Forum rules
Here is the place for you to ask questions about or share your experiences about servicing or repairing your Ural or Dnepr. Please post topics concering modifications or accesories in the "Modifications and Acessories" section. Please post oil related questions in the "Oil Threads" section.
Post Reply
gadge
New Member
New Member
Posts: 19
Joined: Tue Jun 12, 2018 2:48 pm
Location: France

Dneipr running at last BUT

Post by gadge » Fri Mar 15, 2019 8:20 am

Ok guys ,
some time ago we bought a MT-16 which holed a piston ( you may have read my post) ,since then we have had many ups and downs , mostly downs . We could not get it to run at all ,so did away with most of the new bits we had bought went back to the old stuff but remodelled , and it started first kick. Ho the joy, but after a few moments the left hand cylinder started to smoke ( a lot) , but no worries as we were going to completely rebuild it over the winter, which we have now done.
When we dismantled the left hand cylinder ( again ) we noticed a small piece of the lower oil ring had broken , a bit disappointing as they are all new, but at least we thought we had found the problem....
Well started it today after replacing new rings again, and again it started first kick ,and again started smoking badly from the left side. And the same as last time oil coming out of the exhaust.
So any ideas please , we have checked the valves and they fit well , we have honed the barrel and checked the ring gap and all is correct. So not sure if it's valve guides or some thing there abouts .
So before we start again on the left side we just thought we would ask if any one had some idea or knowledge of this problem so we can buy the right part .
Cheers Gadge
Born to ride, Forced to work

Dnepr MT16
Ducati 916
Ducati 600
Suzuki Savage bobber 650
TDM 850
Honda Dax

rivers
Hero of the Soviet Union - 2019
Hero of the Soviet Union - 2019
Posts: 9407
Joined: Sat Jul 24, 2010 10:04 pm
Location: 48*N, 122*W

Re: Dneipr running at last BUT

Post by rivers » Fri Mar 15, 2019 9:48 am

I don't know zip about Dneprs or why your rings keep breaking but my first thought would be when you installed the new rings did you use a new piston or if old piston was used, you cleaned out the ring lands absolutely clean and in spec? Serious smoking before you broke your new rings cold be a plugged oil return drain in the head allowing oil to pool in the rocker box and travel down the valves? Could be sludge or head gasket blocking the drain hole on the offending side?
Joe
014 GU
"I'm lost but I'm making good time."

User avatar
propwash
Order of Lenin
Order of Lenin
Posts: 1615
Joined: Wed Jul 18, 2007 11:45 pm

Re: Dneipr running at last BUT

Post by propwash » Fri Mar 15, 2019 10:03 am

If it smokes right away, I doubt it is the valve train. It takes time for enough oil to build up for that. Even a blocked return tube would take time. This can be tested by removing the valve cover right after the smoking and seeing if excessive oil is present in the head.
A cracked head usually will smoke a bit, but generally once it is warm.
The immediate smoking would likely be ring related.

rivers wrote:
Fri Mar 15, 2019 9:48 am
Could be sludge or head gasket blocking the drain hole on the offending side?
This scenario is impossible with OHV Dnepr.

gadge
New Member
New Member
Posts: 19
Joined: Tue Jun 12, 2018 2:48 pm
Location: France

Re: Dneipr running at last BUT

Post by gadge » Fri Mar 15, 2019 11:26 am

Thanks for the reply's .
The pistons are new and the rings are new .
I have been looking at it today and have taken off the head and barrel just to see, and the piston and rings this time are fine, i have check the gaps of them in the bore and all full well within the guide lines and the barrel looks fine.
There is no blockages any where ,have just checked again ( has you do) but there was a normal amount of oil in the rocker box but quite a bit in the cylinder head and exhaust port, but not a abnormal amount in the bore . So i think i well rebuild the head as the exhaust valve spring seems quite weak so might as well do the lot to be sure.
Thanks again
Born to ride, Forced to work

Dnepr MT16
Ducati 916
Ducati 600
Suzuki Savage bobber 650
TDM 850
Honda Dax

User avatar
propwash
Order of Lenin
Order of Lenin
Posts: 1615
Joined: Wed Jul 18, 2007 11:45 pm

Re: Dneipr running at last BUT

Post by propwash » Fri Mar 15, 2019 11:57 am

What is the ring gap?

DneprTim
Party Member
Party Member
Posts: 165
Joined: Wed Nov 07, 2007 9:29 am
Location: Virginia

Re: Dneipr running at last BUT

Post by DneprTim » Fri Mar 15, 2019 7:49 pm

Make sure the gaps in the rings are not lined up …

gadge
New Member
New Member
Posts: 19
Joined: Tue Jun 12, 2018 2:48 pm
Location: France

Re: Dneipr running at last BUT

Post by gadge » Sat Mar 16, 2019 4:15 am

The gaps are a tight 0.30mm, and the Dneipr book say's between 0.25 and 0.50 , it say's that in the English book and the French book and Russian.
Yes i made sure the gaps are not in line and there is no gaps out all between the wall of the barrel and the rings.
Born to ride, Forced to work

Dnepr MT16
Ducati 916
Ducati 600
Suzuki Savage bobber 650
TDM 850
Honda Dax

User avatar
Claus
Hero of the Soviet Union - 2019
Hero of the Soviet Union - 2019
Posts: 479
Joined: Sun Jan 04, 2015 1:19 pm
Location: Germany
Contact:

Re: Dneipr running at last BUT

Post by Claus » Sat Mar 16, 2019 9:48 am

gadge, you might want to make shure, it´s not old oil in the exhaust that´s smoking.
I would take the complete exhaust down tubes off and start the engine.
There are two things you can detect now:
idle mixture: yellow flames: too ritch, Bunsen blue flames: correct
Oil smokes: if it smokes instantly you know it´s something wrong with piston or rings. If no oil smoke appears, the oil is in your exhaust.

Have you made shure, your pistons are within tolerance talking about install clearence? It should be between 0,08 and 0,10mm . The piston should be measured 90° to the wrist pin hole and appr. 10 to 15 mm from the lower edge (the open side). That´s where the widest point is of a cool piston.
Once warmed up, the piston should become cylindrical. I had plenty of Dnepr pistons in the late 90ies, that went oval and taper when warm. If that happens, the piston can´t seal the combustion chamber to the crankcase and oil smoke appears. Sometimes this causes broken rings as well.

Some of those pistons lost shape completely while holding in hand for some seconds. They were made of "Coke-can aluminium" :-)

The barrels should be measured at three points in X and at three points in Y direction (from bottom to top and turned 90° from bottom to top)
So you can see taper and ovality. Maximum taper and ovality is 0,030 mm
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

gadge
New Member
New Member
Posts: 19
Joined: Tue Jun 12, 2018 2:48 pm
Location: France

Re: Dneipr running at last BUT

Post by gadge » Sun Mar 17, 2019 4:14 am

Thanks Claus,
I think you might be on the right track, the standard of the bits i have brought has been very poor and i have had to make things fit or throw them away. It took along time to make the wrist pin fit the piston it came with because of bad casting and i think the holes are not quite in line ,but will check that.
thanks again
Born to ride, Forced to work

Dnepr MT16
Ducati 916
Ducati 600
Suzuki Savage bobber 650
TDM 850
Honda Dax

User avatar
Lmo
Hero of the Soviet Union - 2019
Hero of the Soviet Union - 2019
Posts: 4833
Joined: Wed Jun 10, 2015 3:19 pm
Location: Central California via So. Indiana

Re: Dneipr running at last BUT

Post by Lmo » Sun Mar 17, 2019 6:26 pm

I nominate Claus for Kavalier der Straße.
Lew Morris
Dnepr w/ '06 Ural Drive Train
C5 Power Arc
125/42 jets
Drilled slides/
.030" shims

1973 BMW R75/5 (original owner)
1947 HD FL (long gone, forever regretful)

User avatar
Claus
Hero of the Soviet Union - 2019
Hero of the Soviet Union - 2019
Posts: 479
Joined: Sun Jan 04, 2015 1:19 pm
Location: Germany
Contact:

Re: Dneipr running at last BUT

Post by Claus » Mon Mar 18, 2019 6:14 am

Too much of an honor, Lew

gadge,you can buy reasonable Dnepr parts at ural-hamburg.de in Germany. They sell Almot pistons that should do well in different sizes
https://www.ural-hamburg.de/index.php?l ... ram=kOLBEN
And they sell the usual crap if you want to buy really cheap :D

Also available: Whole set of pistons, barrels, rings, wristpins,clips
https://www.ural-hamburg.de/Dnepr-Teile ... ER%20dNEPR
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

gadge
New Member
New Member
Posts: 19
Joined: Tue Jun 12, 2018 2:48 pm
Location: France

Re: Dneipr running at last BUT

Post by gadge » Mon Mar 18, 2019 1:40 pm

Well Claus,
you are right , i did some checking on the new piston and you were spot on , have replaced it with a better one and voila no smoke, no oil , so thanks again and if you know any one who want's 4 new crap piston ashtrays ( 5 if you count the one with the hole in it) i'm the man
Thanks for the links , i will check them out.
Born to ride, Forced to work

Dnepr MT16
Ducati 916
Ducati 600
Suzuki Savage bobber 650
TDM 850
Honda Dax

User avatar
Claus
Hero of the Soviet Union - 2019
Hero of the Soviet Union - 2019
Posts: 479
Joined: Sun Jan 04, 2015 1:19 pm
Location: Germany
Contact:

Re: Dneipr running at last BUT

Post by Claus » Mon Mar 18, 2019 6:08 pm

gadge wrote:
Mon Mar 18, 2019 1:40 pm
have replaced it with a better one and voila no smoke, no oil ,
Great you could solve your problem, gadge!
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

Post Reply