BMW K bikes (Bricks)

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1Back to top Go down    Valve stem seals on Tue Mar 28, 2017 5:37 am

andyldean

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Hi,

After a bit of advice.
I have two k100's a 4v and a 2v.
They are both burning a little oil after startup and during running.
The 2v especially burns oil on overrun, which to me indicates valve stem seals?
Both these bikes have sat in storage for long periods of time in the past so I'm guessing again stem seals.
Can these seals be replaced without removing the head? I know some engines allow this but unsure of the K100.
Thank in advance


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1987 K100RT (cafe racer)
1991 K100RS (soon to be my sons cafe racer)
    

2Back to top Go down    Re: Valve stem seals on Tue Mar 28, 2017 7:12 am

charlie99

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would be a bit tricky ...as you have to pull the springs and lifters , collets etc ...I have read of a technique that involves using some rope down the spark plug hole to fill the bore between the piston and the valves - combustion chamber and very slowly advancing the piston up to fill the gap ...obviously with out to much pressure...then you might be able to pull the seals without dropping a valve somewhere sensitive ....but generally the stem of the valve is sufficiently long enough to manage doing the job ...as long as the piston is near tdc before starting on that cylinder ...you would need a long tube spanner to punch the seals home over the valve stem onto the guides though ...from memory about 11- 12 mm .
I would still worry about that accidental impact though ..so the rope thingy might give some cushioning

a bit tricky

but why don't you pull the head an resurface the seats and valve faces ...I would expect that the exhaust valves will be pitted badly to start with ..usually with good regression ..that needs resurfacing to seal properly



I would expect that with the nicasil bore and rings that they would need some work to clear the build up of crap around the ring lands and let themn startto seal better ..rather than running on the varnish of yesteryear inside it all .

if your thinking about doing the resurfacing of the valve faces ...get the machinist to "top the valves" by about 10 thou , if they do the cutting right to seats and valves 10 thou could be about right to keep near valve clearances near original ...very helpful not to have to be chasing new shims for the clearances...takes a real pro to get that right --first time .

good luck


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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
    

3Back to top Go down    Re: Valve stem seals on Tue Mar 28, 2017 7:27 am

Dai

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Better pull the head and check the valve seats at the same time. It really is not a difficult job - the K100 is a mechanic's engine.


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

4Back to top Go down    Re: Valve stem seals on Tue Mar 28, 2017 7:45 am

RicK G

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Wack compressed air in the chamber, 100psi will keep the valve just where it should be and if you lock it at TDC the valve wont fall very far, about 5mm at most and will most likely bang shut very quickly.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

5Back to top Go down    Re: Valve stem seals on Tue Mar 28, 2017 7:49 am

Laitch

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If you've only put hundreds and not thousands of miles on these bikes in the past year, they might smoke less if ridden more. These bikes respond poorly to idleness.


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1995 K75T 68,000 miles
    

6Back to top Go down    Re: Valve stem seals on Tue Mar 28, 2017 10:18 am

Point-Seven-five

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Pulling the head isn't that bad on the brick engine. I did my valve guide seals last year and didn't even have to remove the fairings beyond the belly pan and the left side lower.

At 106,000 miles the valves and seats were still in good shape so all I had to do was clean up the carbon deposits. Outside of a broken cylinder head bolt the job was surprisingly easy, tools purchased on the internet(spring compressor and valve seal tool) only cost cost me $15 after I resold them.

Had it not been for the shipping time on tools to remove the broken bolt I could have done the job in a weekend.

In retrospect, I wish I had taken the extra time to pull the pistons and clean up the oil control rings. While the oil consumption has been reduced, smoking stopped and the compression is very good, the engine still uses more oil than I like(about a quart every 800 miles) and I have to decide if the cost of the extra oil consumption is worth going back in to work on them.


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Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

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