BMW K bikes (Bricks)

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1Back to top Go down    Why does it do this some times? on Thu Mar 23, 2017 2:49 pm

JGT

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I have a very tidy well looked after 1987 K75s showing 85,000 miles and an extensive service history. It runs well. After a days use it is always parked on its centre stand. It can stand for a week or a month unused. Nine times out of ten it will start with a completely clean exhaust. Today after standing a week it smoked, why? Is it the way the pistons come to rest from the previous stop, some times causing a partial vacuum? It does not consume oil in regular use. No big deal, just puzzles me. John


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1987 K75s 1969 Bultaco Matador
    

2Back to top Go down    Re: Why does it do this some times? on Thu Mar 23, 2017 3:45 pm

92KK 84WW Olaf


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Oil behind the pistons can lodge in the bore...as the engine cools the piston ring end gap opens as the metal contracts and shrinks.....oil can flow through the gap up into the combustion chamber. Just depends on what point the crank stops at and where the end gaps are...very commonwith usingside/kick/prop stand but does happen on centre/main stand as well to a much lesser degree. Some of us kill the engine and hold bike upright for a moment before letting it over. Odds are that you first drop it to the left on the side stand before you get off the bike and then lift it onto the centre stand but some oil can be left in the bore below the piston......

Or some bugger might have poured oil in your exhaust, a well known prank on early Honda 4 owners...oil in one pipe...and wait for them to fire it up.....


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1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 84,100 miles
    

3Back to top Go down    Re: Why does it do this some times? on Thu Mar 23, 2017 3:53 pm

Ringfad

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This thread might be of interest

http://www.k100-forum.com/t4297-pinned-rings-in-87-k75-possible

My K100RS 87 also smokes at times but never appears to use any oil.


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;BMW;K100RS Style Black 1987 99K Km ;BMW; K1 Black 1993 42KKm ;BMW;K1100RSRed 1993 50k miles
    

4Back to top Go down    Re: Why does it do this some times? on Thu Mar 23, 2017 5:17 pm

Motorbike Mike

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I had a 1984 K100 with only 4500 miles and that did exactly the same. My opinion was valve stem oil seals, they harden off over time and if it's only the occasional puff of smoke why worry?

    

5Back to top Go down    Re: Why does it do this some times? on Fri Mar 24, 2017 6:50 am

Holister

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Is it possible you have a smidge too much oil in the crankcase. Easy to do if your sight glass has gone nearly opaque.


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1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

6Back to top Go down    Re: Why does it do this some times? on Fri Mar 24, 2017 8:09 am

charlie99

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@Motorbike Mike wrote:I had a 1984 K100 with only 4500 miles and that did exactly the same. My opinion was valve stem oil seals, they harden off over time and if it's only the occasional puff of smoke why worry
we call it "marking her territory " amongst the "krew" members

I'm fully over the smoke on restart issue ...sheesh

but constant progressive good habits tend to minimise this issue ....by idling for just a short while /with both feet down ...and waiting for about 10 -15 seconds before dumping onto the sidestand after switch off ...do tend to minimise the issue



what do you think the chances are of any of these machines smoking after start ? 2- 10 perhaps ?

all I know is ...its given me cause to grow thicker skin and resist the comments .....grin

nothing bad about riding a classic with all its good and bad points


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

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