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piston swap

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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-12          157835


Anyone know if you can swap a piston from a 400 series air cooled Belarus into a 250? I've got a 250 that burns oil big time and the last owner said he did a ring job then couldn't get it started.Thats when I came alone and bought all his problems. Dealer and myself thought it might seat the rings in a few hours but not so, run about 30 hrs hard work on bushhog and burns about 2 litres in 3 hrs, foggy. I suspect he used either to try and start it and maybe broke a ring or two and maybe a piston land. I know of a wrecked 400 that I can get a piston out of if need be. Curious to know if it would fit. I'll tear mine down next week and if pistons okay I'll hone cylinders (wasn' done) and put in new rings. But I suspect the worst - broken ring or piston.



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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2008-11-12          157840


"I suspect he used either"--I assume you mean ether or starting fluid right?

I'm a little confused why you would swap out the pistons t begin with. If the rings are suspect then why not just replace the rings?

Maybe it wasn't the rings to begin with. Maybe it's the valve guides. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-12          157842


Of course won't know till I tear it down but I've seen the inside of engines started with either. On one it broke not only the rings but the lands in the pistons that the rings sit in. The heads were done by the dealer prior to the last owner doing the rings.

On the piston swap: If they swap it will be scrap price vs dealer price and a some old rings to boot. Piston part numbers should be the same if it will swap - 400 and 250. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-15          157898


update:
Tore the engine down yesterday. Didn't take long at all about an hour and a half. Pistons good, cylinder walls too bright and glazed, no lower oil control ring in groove 5. I will, move oil control ring in groove 4 down to groove 5 and install entire new set of rings in upper grooves. New ring sets only come with 4 rings (3 compression, 1 oil control) and are for the new design piston, deglaze cylinders with hone. Nice little engine to work on, just at waist height. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-16          157918


I hope the picture of the piston made it. I'm just learning to post pictures. ....

Picture Link


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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2008-11-16          157919


Sorry--no it didn't work. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster

2008-11-16          157920


Sorry about that picture. I've been fumbling around in the dark trying to figure out what to put in the 'picture image' box, and how to do it. Read some threads on this site but lack of clear instructions on how to take from my computer file and attach to message. I'll soldier on. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-17          157952


Update:
Culprit found. While moving the upper oil control ring to the lower groove discovered that one of the three rings used in the oil control groove was gone. The oil control ring is really 3 rings in one groove, 2 wipers and one spring ring behind the 2 wipers it pushes the wiper rings into contact with the cylinder wall. This was the rear cylinder and the one smoking most.

The two cylinders cleaned up good and the deglazing worked well. Pick up rings and gaskets wed and install by the weekend. ....


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belarus250
Join Date: May 2008
Posts: 30 NE
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2008-11-22          158072


Finished:
Job done. Got it running today and am very pleased with how clean it burns. It was quite a nice job, things came apart easy - it is a simple little engine. Of course the thing was apart not too long ago. The prior owner did the rings and how it was done was the issue. Cylinders not deglazed, no rings in lower groove, no spring ring in upper oil groove on rear piston.

Oh, while apart I cut off the downward extension of the exhaust pipe from the muffler and re welded it upward to put the exhaust pipe up. This will keep exhaust gas away from the 3pth area and make it bearable for log splitter use.

I hope this helps other readers of this forum in some small way. ....


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vladimirec
Join Date: Mar 2009
Posts: 29 Croatia
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2009-03-05          160818


the belarus 400(d-144engine) and belarus 250(d-120engine)have same engine segments(cilinder,piston,head,valves etc.)just that 400 has 4 of them and 250 2. ....


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