BMW K bikes (Bricks)

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1Back to top Go down   K100 Cylinder head rebuild Empty K100 Cylinder head rebuild on Tue Nov 12, 2019 7:05 am

Chewbacker

Chewbacker
active member
active member
How easy is it to rebuild a 8v K100 head.
Needs valve guides replacing and valves reseating (I think)
Anything else I should be doing please?

    

2Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 7:14 am

88

88
Life time member
Life time member
That depends on whether you have rebuilt a head before. It's very doable for an amateur mechanic.

Follow whatever manual you have for dismantling. Give it to a local engineering place to get the head skimmed/planed and the valve seats re-cut, They might do the guides for you too and lap the valves if you are unsure how to do it.

"Refitting is the reverse of the removal proceedure" as they say in the Haynes Very Happy. Use a good quality torque wrench.

Use a full gasket kit whilst doing it and I would be having a good look at doing the timing chain and/or guides whilst at it.

The real issue is determining why did it go? Until you have determined that it may be a false economy putting the overhauled head back.


__________________________________________________
K100 Cylinder head rebuild Ir-log11 88....May contain nuts!K100 Cylinder head rebuild Ir-log11

"The world is a book and those who do not travel read only one page." - St. Augustine from 1600 years ago & still true!

Bike: K100LT 1988. 0172363. AKA the Bullion Brick! Mods: k1100 screen and stands.
K1: 1990. 6374189. Custom Stealth Black paint.
    

3Back to top Go down   K100 Cylinder head rebuild Empty Head on Tue Nov 12, 2019 7:45 am

Chewbacker

Chewbacker
active member
active member
Thanks for the response.

There's nothing wrong with it except being 35 years old. The valve guides were worn and need replacing.

The head has been stripped just need to get new valve guides and reseat the valves (I think)

What parts should I replace while here?

    

4Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 10:12 am

88

88
Life time member
Life time member
@Chewbacker wrote:Thanks for the response.

There's nothing wrong with it except being 35 years old. The valve guides were worn and need replacing.

The head has been stripped just need to get new valve guides and reseat the valves (I think)

What parts should I replace while here?
You only need to do the valve seats if they are worn beyond re lapping. The last one I got done was a k11 - I got the ports all soda blasted which smoothed them out a good bit too. not quite ported and polished but a nice clean up and free airflow.

I would do the valve guides, valve seals and check all the valve edges to make sure they are all ok to go back in.


__________________________________________________
K100 Cylinder head rebuild Ir-log11 88....May contain nuts!K100 Cylinder head rebuild Ir-log11

"The world is a book and those who do not travel read only one page." - St. Augustine from 1600 years ago & still true!

Bike: K100LT 1988. 0172363. AKA the Bullion Brick! Mods: k1100 screen and stands.
K1: 1990. 6374189. Custom Stealth Black paint.
    

5Back to top Go down   K100 Cylinder head rebuild Empty Valves on Tue Nov 12, 2019 11:32 am

Chewbacker

Chewbacker
active member
active member
Thanks 88. Should I also replace the valves if the vales guides were worn. I'm very conscious of how much each one is!!

    

6Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 1:07 pm

Dai

Dai
Life time member
Life time member
Shame that James & Harmer up at Fleetsbridge seem to have disappeared. They used to make Guzzi valve guides for me - far cheaper than going out to Motomecca at Ferndown Industrial and buying OEM.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

7Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 3:40 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
@Dai wrote:They used to make Guzzi valve guides for me - far cheaper than going out to Motomecca at Ferndown Industrial and buying OEM.
That may be part of the answer you seek.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

8Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 6:42 pm

Dai

Dai
Life time member
Life time member
Until the day I needed three valve guides in a hurry and went up to Motomecca. After some fiddling around with the computer and digging in plastic bins there was a hiss of indrawn breath.

'We've got some in the bins but I can't sell you them. Not on stock control you see'.

Somewhat pissed-off I finished my (shop supplied) coffee just as [REDACTED to protect the guilty/innocent] lined up three valve guides on the counter.

'I did say I couldn't sell you them...'


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

9Back to top Go down   K100 Cylinder head rebuild Empty Re: K100 Cylinder head rebuild on Tue Nov 12, 2019 8:20 pm

K75cster

K75cster
Life time member
Life time member
If you are asking us for what would we do with the head off, then Yes New guides, valve inspection, (by that I mean stem length avareage 111mm stem dia wear limit 6.950 normal 6.975 and valve head runout  sort of rim buckle ovality, the seat detail will tell some of that) Guide internal limit is 7.1mm
I'd have the combustion chambers CC'd and the Port volume equalised. How fussy am I? Yep. But it can pay dividends.

Spring checks and collet check.

My reckoning is if you have to go in there then make it worth your while and finesse the thing to combustible perfection. No one cylinder should do the lions share of the work when your finished. you may even get the engine to equal the throttles factory volumetric sync. That would ensure an incredibly smooth  idle and running engine.


__________________________________________________
Keith - 1987 K75c with r100rt replica fairing and half of a 1984 K100rt 1992 K1100LT a blue one

The Clever are adept at extricating themselves from situations that the wise would have avoided from the outset - QUOTE from david Hillel in Out of the Earth.
    

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