Author Topic: K100 Exhaust Back Pressure  (Read 4449 times)

Offline PaulP

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K100 Exhaust Back Pressure
« on: November 02, 2017, 06:29:38 PM »
Morning / Afternoon / Evening.

I'm going to be indulging in a little jiggery-pokery with the exhaust system on my K100.

Are there any issues regarding back pressure (either too much or too little) which might cause a problem if the engine>silencer distances are altered?

Is the K. engine particularly susceptible to such alterations, or is it robust enough to laugh in the face of untuned pressure waves?

Cheers
  • Scotland, UK.
  • '91 K100 LT. Ex-Polizei.

Offline Martin

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Re: K100 Exhaust Back Pressure
« Reply #1 on: November 02, 2017, 09:15:01 PM »
Various exhaust have been tried on Bricks. And from the reports that I have seen there is nothing to be gained performance wise. The only advantages are weight reduction and noisier if that's an advantage.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline PaulP

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Re: K100 Exhaust Back Pressure
« Reply #2 on: November 02, 2017, 10:18:20 PM »
Thanks for that.

I seek no performance or noise gains, it's just that I want to reposition the exhaust for aesthetic purposes and get rid of the fairly ugly (IMHO) silencer.

In order to achieve this I need to add some length to the manifold pipes, and I was concerned it may have an adverse effect on valves/stems and such like.
  • Scotland, UK.
  • '91 K100 LT. Ex-Polizei.

Offline Chaos

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Re: K100 Exhaust Back Pressure
« Reply #3 on: November 02, 2017, 10:27:17 PM »
I have run a Luftmeister and now a MAC pipe for decades with no ill effects.  I think  the FI brain compensates for backpressure up to a point.  When the baffle blew out of the luftmeister and it became an open cone the engine was not a happy camper. 
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Martin

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Re: K100 Exhaust Back Pressure
« Reply #4 on: November 02, 2017, 10:35:48 PM »
If that is the case I would try and find one of the made for replacement ones. Try looking for a Luftmeister, MAC or Staintune, that way you know that the state of tune will not be adversely effected.
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline PaulP

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  • Posts: 57
Re: K100 Exhaust Back Pressure
« Reply #5 on: November 02, 2017, 10:57:03 PM »
Thank you both.

I've a couple of nice Pan European stainless silencers which I intend to 'make fit', but as mentioned I'll also need to add a few inches to the manifold pipes to get 'em to where I want 'em.

Satisfied that I can make a modest change without the lump exploding into a fiery ball of shrapnel, I shall crack on....
  • Scotland, UK.
  • '91 K100 LT. Ex-Polizei.

Offline billday

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Re: K100 Exhaust Back Pressure
« Reply #6 on: November 04, 2017, 07:05:48 AM »
Never knew that MAC made a K system. Just looked it up at Dime City Cycles. They say that carburetor rejetting may be necessary. So factor that in to your budget.
  • New York State, USA 10977
  • 1985 K100

Offline Chaos

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Re: K100 Exhaust Back Pressure
« Reply #7 on: November 04, 2017, 09:31:42 AM »
They say that carburetor rejetting may be necessary.

Yes, that would be difficult on a K  :hehehe
  • sw ohio
1987 K75S    VIN 0231
Original owner, Original litter
200,000 miles (plus or minus) and 5 paint jobs
sold 6/23
2023 Ural 2WD sidecar (BMW's bastard step child)

Offline Martin

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  • Posts: 4475
Re: K100 Exhaust Back Pressure
« Reply #8 on: November 04, 2017, 03:09:46 PM »
No Chaos, it means that in order to run the exhaust you must fit carbies.  :hehehe
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

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