BMW K bikes (Bricks)

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1Back to top Go down    Other tachometers on Wed Jan 04, 2017 12:53 pm

Marvin M

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Happy new year...  Very Happy

I've got a k75 engine and ancillaries. And pretty much nothing else. 
Eventually if all goes to plan then its not going into a bike. 

Part of the plan is to have a tachometer.
The one from the bike would not suit my needs. So I was hoping to use a type from a 4 cylinder car.
As I understand it (please correct me if I'm wrong) 
The ignition works as a wasted spark system. 
The 3 cylinder K75 has individual coils to each spark plug.
Either on combustion or exhaust its one spark per revolution then.
The tachometer I want will need 2 sparks per revolution to read correctly as it's function is based on 4 cylinders from one coil firing every half stroke.

That is how I understand it. So I believe I need something that will somehow double the signal pulse to get the tachometer to read correctly.

Being fairly comprehensive I doubt this forum has not had the issue raised before. And likely got a solution to it. 
I would have searched the site if I had found a search function. Maybe it's just me not finding it. Is my low use an issue to that?

All help greatly appreciated Smile

    

2Back to top Go down    Re: Other tachometers on Wed Jan 04, 2017 7:50 pm

RicK G

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The tacho on a K75 reads of #3 coil and on a K100 of 2/3 coil so they are the same. The 1/4 coil has no part in the tacho reading. If it works on a K100 it works on a K75.


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"Every normal man must be tempted, at times, to spit upon his hands, hoist the black flag, and begin slitting throats."  from Mencken's 1919 Prejudices

Bikes 1993 K1100 LT, 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 for now
    

3Back to top Go down    Re: Other tachometers on Thu Jan 05, 2017 4:52 am

92KK 84WW Olaf

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Happy New Year too!

Do let us know what its going into............Hover K100 put a K100 engine into a hovercraft.

The flat engine makes for lots of alternative uses............


__________________________________________________
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 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

4Back to top Go down    Re: Other tachometers on Thu Jan 05, 2017 7:02 am

Marvin M

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@92KK 84WW Olaf wrote:Happy New Year too!

Do let us know what its going into............Hover K100 put a K100 engine into a hovercraft.

The flat engine makes for lots of alternative uses............
I do plan to. 
But when I read forums I see a lot of unfinished projects. Usually because the work on them become more than they anticipated. 
So why it's in, when it's in (and running) will be when I get round to letting on. Kinda my way of having motivation to finish it.

    

5Back to top Go down    Re: Other tachometers on Thu Jan 05, 2017 7:10 am

92KK 84WW Olaf

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Looking forward to that.

The two areas you want to watch out for are the rear main seal, behind the flywheel and also the oil/water pump if it wasn't done by a previous owner. The rear seal is a very cheap part, the water pump parts if you needed a shaft is probably close to £150 or so. Care is needed doing it because the seal is ceramic and easily broken during installation.

K engines are very reliable and trouble free.

Do you plan on retaining all the engine electrics as in fuel injection system etc?


__________________________________________________
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 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

6Back to top Go down    Re: Other tachometers on Thu Jan 05, 2017 8:13 am

Marvin M

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Yes. It's size, reliability and all round tractable nature of the engine was a key decision of why I'm using it. So both the ignition and fuel injection  ECUs are being retained.

    

7Back to top Go down    Re: Other tachometers on Thu Jan 05, 2017 8:45 am

92KK 84WW Olaf

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Sounds like a good project and more than me will be curious about it. Best of luck with the project.


__________________________________________________
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 84,600 miles
1983 K100RS 0011175 Fricka 29,000 miles Damn K Pox
    

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