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Luca
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Piemonte NW Italy
Joined: 04/18/2007
Posts: 13

Hello,i replaced in my R90s, valves guides,pistons rings and honed the cylinders, since the engine had low compression and consumed so much oil. Now I have about 3000 km but the bike smokes a lot and still consuming oil, the engine resumed compression and works very well.
I forget to say that all mechanical measurements are right (I suppose the mechanic has checked them correctly)
Do you have any advice?
Thank you

Best regards
Luca

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brownbmw
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VBMWMO #7491
So. Cal.
Joined: 01/03/2009
Posts: 89
There are only a few places

There are only a few places oil can go. I'll assume it's not leaking out as you would see it, and that wouldn't explain the smoking. If you are correct that the valves, guides, pistons, and rings are new and done correctly the next most likely cause is the breather valve. Is the smoking mostly on the right side? The breather dumps excess oil into the right carb.

Barring that, you can do a leak-down test on the top ends to see if there is excess leak-down, which would mean the top ends still have issues.

Luca
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Piemonte NW Italy
Joined: 04/18/2007
Posts: 13
The smoke is the same,right

The smoke is the same,right and left.I don't have smoke after downhill,i have smoke after small stop and also ,when i run, if i open smoothly the gas.

Best regards

Luca

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schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6505
Usually if it smokes when

Usually if it smokes when going downhill with closed throttle, that would mean valves/guides. If it smokes on acceleration, that would mean rings.

What was your break-in procedure?

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

Luca
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Piemonte NW Italy
Joined: 04/18/2007
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I drived not up 3000rpm first

I drived not up 3000rpm first 100 km and after sometimes till 4000 rpm and change speed very often .It seems that i have smoke in a situation in middle of two: it smokes in smooth acceleration,specially after a short stop that run idle.I tried different oil but it's the same.I need 1 kg for 1000 km,very much.

Best regards
Luca

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schrader7032
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VBMWMO #7032
San Antonio, TX
Joined: 10/27/2006
Posts: 6505
Did you vary your speeds up

Did you vary your speeds up to 3000 RPM? Did you accelerate and decelerate? Deceleration is important because the pressure forces the rings against the cylinder walls. The initial start IMO is very important as a good portion of break-in happens there.

At only a 3000KM (~1800 miles), there's probably some more break-in to happen.

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Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2

RickR90s
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Farmington Hills, MI
Joined: 11/28/2016
Posts: 63
can you tell us which rings

can you tell us which rings were used on the rebuild? Especially the oil rings? Were they stock or aftermarket 3 piece oil control rings?

If they were 3 piece, I'll share a horror story that happened on my brother's R80/7, where it never stopped smoking, using a quart of oil in 150 miles. Yes, 150 miles.

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RickR90s

Luca
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Piemonte NW Italy
Joined: 04/18/2007
Posts: 13
I used piston ring set from

I used piston ring set from "GOETZE" that is also a supplier for BMW.There are 3 as pistons need 3
What happened to your brother?

Best regards
Luca

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RickR90s
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Farmington Hills, MI
Joined: 11/28/2016
Posts: 63
he installed 3 piece oil

he installed 3 piece oil rings. This configuration uses and internal spring and two scraper rings to push the rings tighter against the cylinder. he had the local dealer do it and they screwed up. When we disassembled, the spring had a red and green mark painted on each open end. The dealer must have thought that the green part went over the red part, but in fact, the two parts just mated together, keeping maximum spring tension on the rings. Since they overlapped them, spring pressure was minimal and the bike smoked.......bad.

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Luca
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Piemonte NW Italy
Joined: 04/18/2007
Posts: 13
I underdtood.May be it wasn't

I underdtood.May be it wasn't original kit,mine is a little different 2 piece oil ring:

once the spring is inside you must turn it

  • img_4988.jpg
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Un lampeggio a tutti!
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