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1Back to top Go down    seriously low compression 1986 BMWk100 on Sat Feb 04, 2017 4:28 pm

wilbo

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Hi guys, i'm a newbie K100 owner, purchased a non runner with electrical fault to restore during UK winter. Anyway I sorted the electrical fault in 24hrs, starter motor needed polishing up and I have the bike running, starts first time and sounds lovely! As i'm going to take frame away from engine and have it blasted and painted I thought I would do an initial compression test before I check valve clearences and see condition of engine incase I need to carry out any engine work when I have the oppourtunity.

I warmed the engine up, then carried out the compression tests and all circa 80-85psi! Does anyone think valve adjstments will make a huge improvement? I'm going to take cover off and check clearences but I am not convinced. As my bike is a 1986 model i'm thinking it maybe a leaded/unleaded valve issue on the cylinder head, any views off you experts? The bike says 42,000miles and is in good condition for 31years old,does not look like it has had a hard life but as we all know many a clock failed!

Any pointers for me??

Thanks in advance

    

92KK 84WW Olaf

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All circa 80-85 suggests either the gauge is defective, not correctly sealed or not fully tightened home to seal it. Consistency suggests this is a strong possibility and try another gauge before worrying about the outcome. A check on valve timing might be wise too but try another gauge frist.

I think 86 should be ok for leaded fuel too.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

Dai

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What Olaf says.


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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)
    

wilbo

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@92KK 84WW Olaf wrote:All circa 80-85 suggests either the gauge is defective, not correctly sealed or not fully tightened home to seal it. Consistency suggests this is a strong possibility and try another gauge before worrying about the outcome. A check on valve timing might be wise too but try another gauge frist.

I think 86 should be ok for leaded fuel too.
Thanks for reply, I shall carry out another test tomorrow. More worrying though is the fact I have followed a link to when bikes were manufactured from this website, it appears mine may have been registered in 1986 but manufactured in 1983..... My frame number is 0003361 which points to bike being manuafactured between 10/83 & 11/83 which I think means it should be for unleaded.


__________________________________________________
Current Stable
1983 BMW K100
1996 BMW R100RT
2009 Honda CBF1000
2003 Aprilia RS250
1996 Kawasaki GPZ500s
1955 James Colonel 225cc
    

92KK 84WW Olaf

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Mine also is the earlier one and has just short of 80,000 miles and runs ok on the unleaded fuel. I think unless you are riding really hard this will not be an issue.

Dai has a lot more mechanical knowledge than me!


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

wilbo

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@92KK 84WW Olaf wrote:Mine also is the earlier one and has just short of 80,000 miles and runs ok on the unleaded fuel. I think unless you are riding really hard this will not be an issue.

Dai has a lot more mechanical knowledge than me!
Hi, thanks for reply. I have just confirmed also from the engine number that it was built in week 43 of 1983 so is designed for Leaded. I dont inten to use it to hard but I am going to give it a full restoration and was also intending to use it for touring on, would not want a burnt out valve in the middle of no where! I may have to continue using my R100RT for that. I may also look at getting a topend from an unleaded one if I can pick one up.

    

92KK 84WW Olaf

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I would have been more worried if one of the cylinder readings was way off, that would point to a problem in that particular cylinder, possibly valve but a badly burned valve would lead to very low compression.

Don't come to any conclusions without another test, redo it maybe but also go for another gauge and come back to the forum.

If memory serves me right its about 10.2 to 1 or about 150psi.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

Laitch

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@wilbo wrote:My frame number is 0003361 which points to bike being manuafactured between 10/83 & 11/83 which I think means it should be for unleaded.
What is your source for the information that this engine is one of those designed for unleaded, wilbo?


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1995 K75T 68,000 miles
    

Dai

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I've racked up almost 45,000 miles on mine in the last four years. I did a valve check at about 75,000miles (it's now at almost 85,000 miles) and found nothing wrong. Mine's a November '83 model.


__________________________________________________
'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)
    

10Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sat Feb 04, 2017 10:18 pm

Point-Seven-five

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Dumb question here, but are you holding the throttle open for the test? If not, give that a try.

Another thing, is the air filter clean and the MAF flapper swinging freely? Any rodent residences in the airbox?


__________________________________________________
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
    

11Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 12:11 am

charlie99

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good point .75 wot (wide open throttle )is required for this test


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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
    

12Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 8:36 am

wilbo

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@Point-Seven-five wrote:Dumb question here, but are you holding the throttle open for the test? If not, give that a try.

Another thing, is the air filter clean and the MAF flapper swinging freely? Any rodent residences in the airbox?
I love dumb questions!!! It's 2 years since I did a compression test and totally forgot to open the throttle! Just been out, ran bike to temperature and carried out test again. Here are my results

Cylinder 1 - 135psi
Cylinder 2 - 135psi
Cylinder 3 - 145psi
Cylinder 4 - 145psi

May have ran the starter a bit more on last 2 cylinders but the compression does not look that bad to me for a 33 year old bike!!

Thanks for all your help fellas, much appreciated.

    

13Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 11:39 am

92KK 84WW Olaf

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With those readings I think I would be putting the tester back in its case and carrying on with riding the bike. 145 is about 10:1 and I cant see it being worth doing anything other than checking valve clearances. I thing that's all I would do and carry on riding.

What is nice about the forum is that somehow the right answers come out. The first readings were fairly consistent across all cylinders and it would seem that your K is indeed a nice one.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

14Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 11:56 am

wilbo

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@92KK 84WW Olaf wrote:With those readings I think I would be putting the tester back in its case and carrying on with riding the bike. 145 is about 10:1 and I cant see it being worth doing anything other than checking valve clearances. I thing that's all I would do and carry on riding.

What is nice about the forum is that somehow the right answers come out. The first readings were fairly consistent across all cylinders and it would seem that your K is indeed a nice one.
Hi Olaf, thanks for the reply. Yes I was a bit shocked to see the huge increase in compression, almost to specification as in my Haynes&Clymer manual. I almost agree I maybe just creating a load of work for myself dropping engine out to get the frame blasted and painted, but the bodywork has lots of scratches and chips on it also which lets it down and I like to have a nice looking bike. I may just put it in for an MOT out of interest and see what happens!

The engine casings look in fantastic condition and I know it was well looked after as the last owner had it for 10 years and was meticulous in his maintenance, splines, oil/filter, fuel/filter etc etc and always stored inside.

I could just put it on road for spring and use it for a year I suppose to see if it does have any issues before I tear it down.

    

15Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 12:31 pm

Point-Seven-five

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You could probably describe me as anal-slothful. I like to have a nice looking bike, but would rather not kill myself getting there.

Instead of dropping the engine have you tried cleaning up the nasty spots on an individual basis. One of the worst is under the tail cowling. I have been very successful masking off and doing touchups on the frame using Rustoleum satin black from a rattle can.

You can do one spot at a time, usually in a day or two, and be off riding in between. Keeps the rust at bay, and the frame looking good for a minimum investment in time and cash.



Last edited by Point-Seven-five on Sun Feb 05, 2017 12:33 pm; edited 1 time in total (Reason for editing : speling airur)


__________________________________________________
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
    

16Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 12:43 pm

92KK 84WW Olaf

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My RT looked a bit sad when I got it.

Swapped the heat shield with a spare I had for the LT, it needed a piece cut ut but looked a lot better than the battery acid damaged one I took off at the time.

Cleaned and repainted the frame on the battery vent side, over the heat shield, it was badly acid corroded and used a brush paint in satin black. Will do the rear under the rear cowl this year and replace the seat lock with a nice new one that came courtesy of BobT in 88's travel bag. I have done some other parts of the frame as Point Seven Five suggests, a nice day and do it outside on the patio.....and enjoy the ride in between. Would I drop the engine to paint it? No way, not when we can ride all year.....I would differ if we couldn't ride in winter.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

17Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 1:00 pm

wilbo

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@92KK 84WW Olaf wrote:My RT looked a bit sad when I got it.

Swapped the heat shield with a spare I had for the LT, it needed a piece cut ut but looked a lot better than the battery acid damaged one I took off at the time.

Cleaned and repainted the frame on the battery vent side, over the heat shield, it was badly acid corroded and used a brush paint in satin black. Will do the rear under the rear cowl this year and replace the seat lock with a nice new one that came courtesy of BobT in 88's travel bag. I have done some other parts of the frame as Point Seven Five suggests, a nice day and do it outside on the patio.....and enjoy the ride in between. Would I drop the engine to paint it? No way, not when we can ride all year.....I would differ if we couldn't ride in winter.
It's not that bad a bike really and if i'm honest i'm going over the top, mainly because I want to! I've plenty of other bikes to ride but I have a feeling i'm going to like this one a lot! Especially if I can find a decent screen for it for touring.


__________________________________________________
Current Stable
1983 BMW K100
1996 BMW R100RT
2009 Honda CBF1000
2003 Aprilia RS250
1996 Kawasaki GPZ500s
1955 James Colonel 225cc
    

18Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 2:23 pm

92KK 84WW Olaf

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BMW K100 Basic

05/82

0000001

0000019

N/A

N/A

"

04/83

0000020

0000040

N/A

N/A

"

05/83

0000041

0000146

N/A

N/A

"

06/83

0000147

0000259

N/A

N/A

"

08/83

0000260

0001015

N/A

N/A

"

09/83

0001016

0002593

N/A

N/A

"

10/83

0002594

0004094

N/A

N/A


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

19Back to top Go down    Re: seriously low compression 1986 BMWk100 on Sun Feb 05, 2017 2:35 pm

92KK 84WW Olaf

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I take it that yours is a K100 basic from the numbers showing up, 10/83.

There are some screens available and others on the forum might have more information on these.

But a thing to keep in mind is that RT/LT fairings are rather effective for touring and they keep coming up for sale. You would need a few other items with such a fairing, change of handlebars, clutch cable, throttle cable, front brake pipe from the master cylinder, headlight. This would be great for touring.


__________________________________________________
1992 K100LT 0193214 Bertha Alaska Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 58,645 now 82,800 miles
    

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