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Author Topic: Bringing K75 back from the dead.  (Read 18762 times)

Offline daveson

  • ^ Quintessential Motobricker
  • Posts: 1122
Re: Bringing K75 back from the dead.
« Reply #25 on: May 13, 2019, 02:33:50 AM »
  :popcorm
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #26 on: May 13, 2019, 02:36:02 AM »
Be old and love it.  It took me about  a year before I posted a photo, the first was a stuff up.  :popcorm
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Sopp

  • Motobrick Curious
  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #27 on: May 13, 2019, 02:57:06 AM »
I have no idea what I’m doing wrong posting pictures.  Here’s a rear view of the bike.
Will take a picture of the manifold tomorrow.

Sopp
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Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #28 on: May 13, 2019, 03:32:50 AM »
Love the seats too.

The last two photos are the right way up from down under.  :popcorm
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #29 on: May 13, 2019, 05:49:05 AM »
Did you reconnect the hose that went from crankcase to plenum chamber?  Originally it's a large diameter without a PCV type valve. How did you block the injector holes?
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Sopp

  • Motobrick Curious
  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #30 on: May 13, 2019, 05:00:59 PM »
One more try . You can see the plugged crankcase hose in the right side of the picture ( unless it is up side down ).  So that is not the problem.
Two more pictures.
I figured out how to post more than one picture. Hip hip hurray!!!".............maybe.........
Sopp
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Offline JPaganel

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  • Posts: 184
Re: Bringing K75 back from the dead.
« Reply #31 on: May 13, 2019, 05:17:32 PM »
1. Is that duct tape covering the injector ports? That would leak like a bastard.  Or are those injectors under there?
2. Why do you have this long horizontal runner? Why not mount the carb closer to the intake boots?
3. How sure are you the manifold doesn't leak air?
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  • Minnesnowta
  • 1986 K100RT, 1996 R1100RS

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #32 on: May 13, 2019, 05:25:58 PM »
+1
I know this doesn't make sense but I spose the Carby seems in the way if mounted on the mounting side.

Plus how sure are you the butterfly remains closed.

Could that set up be like a huge venturi? Does the throttle grip (or whatever you got)  remain stationary when it shoots from idle to 8000rpm?
 :popcorm
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline JPaganel

  • ^ Proficient Motobricker
  • Posts: 184
Re: Bringing K75 back from the dead.
« Reply #33 on: May 13, 2019, 06:05:18 PM »
Quote from: daveson on May 13, 2019, 05:25:58 PM
+1
I know this doesn't make sense but I spose the Carby seems in the way if mounted on the mounting side.

It's still sticking out the side on the right.

My rationale in asking this is that shorter pipes with fewer joints are less likely to be leak sources.

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  • Minnesnowta
  • 1986 K100RT, 1996 R1100RS

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #34 on: May 13, 2019, 06:13:01 PM »
Yep. Your right.
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline JPaganel

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Re: Bringing K75 back from the dead.
« Reply #35 on: May 13, 2019, 06:50:45 PM »
Quote from: daveson on May 13, 2019, 06:13:01 PM
Yep. Your right.

Nope. He is right. I'm left. (if you are talking carb placement)   :laughing-on-ground:
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  • Minnesnowta
  • 1986 K100RT, 1996 R1100RS

Offline billday

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Re: Bringing K75 back from the dead.
« Reply #36 on: May 13, 2019, 08:35:31 PM »
Quote from: daveson on May 13, 2019, 03:32:50 AM
Love the seats too.

+1 on the seats. Too cool.

That pic Laitch posted shows other people have done carburated K bikes. Some diligent Googling might turn up some helpful info.

What is the gas tank off of?

The angle of the drive shaft is pretty severe, but not sure what you could do about that.
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  • New York State, USA 10977
  • 1985 K100

Offline Sopp

  • Motobrick Curious
  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #37 on: May 14, 2019, 12:37:35 AM »
I’ll try to answer some questions, without using upside down pictures.

1. Injectors are still there, duct tape just keeping dirt out of hole.
2. Damned if I remember why I put the carb on that side. There was a good reason at the time.
3. 99% sure the manifold does not leak. I’m gonna pull it off and check every joint.
4. Air cleaner has been off and I watch the throttle plates while it revs up........they are closed.
5. It is the original tank, just widened and made deeper.
6. Driveshaft turns freely when spinning rear tire. Not sure about longevity.
7. The seats go along with the retro design, same with the 53 Caddy rear fenders, and the 34 Ford pickup rear fenders covering the front wheel ( from the upside down drawing)

On picture of rear end, 318i had drum brakes which I eliminated and replaced with 2 K75 rotors and calipers mounted inboard.  I just love building things.  I’m using ALL BMW parts to build this thing. Other than the retro stuff, this is what BMW should have built a long time ago.  They had all the parts.

Thank you again for all your help and patience,
Sopp
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Offline JPaganel

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Re: Bringing K75 back from the dead.
« Reply #38 on: May 14, 2019, 01:08:01 AM »
Quote from: Sopp on May 14, 2019, 12:37:35 AM
I’ll try to answer some questions, without using upside down pictures.

1. Injectors are still there, duct tape just keeping dirt out of hole.

Thank you again for all your help and patience,
Sopp

Are you sure the injector o-rings aren't cooked?
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  • Minnesnowta
  • 1986 K100RT, 1996 R1100RS

Offline Laitch

  • Faster than a speeding pullet
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Re: Bringing K75 back from the dead.
« Reply #39 on: May 14, 2019, 01:24:49 AM »
You aren't using the original high pressure fuel pump to deliver fuel to the carburetor are you? What's the fuel delivery system?  Having the carb intake pipe directly opposite one branch of a three-branch intake creates imbalance. Right now, this project is less like bringing a K75 to back to life and more like like turning a K75 corpse into a zombie. If it develops a lurching, foot-dragging gait, that could define success. :giggles

Since you've made your age part of the reason for this fuel system remodeling, how old are you? Remember, you're only older than the dirt that's above you.
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Sopp

  • Motobrick Curious
  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #40 on: May 14, 2019, 01:40:48 AM »
After market fuel pump delivering 4 to 5 psi.

Good question, I’ll pull them when I check the manifold.  Air has to be getting in somehow. Can’t rev like that without lots of air and fuel. Even if I’m new to BMWs, all engines are still just air pumps with combustion.  All the same principles apply.

I’m 72 years young. My body feels like 90, but my spirit is still 21.  It’s a curse.
If it ‘s gate is like a zombie I’ll just have to build a new manifold.  Cross that bridge when I finally get to ride it.

Sopp
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Offline Laitch

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Re: Bringing K75 back from the dead.
« Reply #41 on: May 14, 2019, 01:56:05 AM »
Quote from: Sopp on May 14, 2019, 01:40:48 AM
I’m 72 years young. My body feels like 90, but my spirit is still 21.  It’s a curse.
If it ‘s gate is like a zombie I’ll just have to build a new manifold.  Cross that bridge when I finally get to ride it.
The real curse is wishing you were 72 when you're 82 and feeling 100—speaking of bridges to cross. :giggles

Although engines are just air pumps, some design principles still apply to multi-cylinder manifolds.
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  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #42 on: May 14, 2019, 05:39:38 AM »
Maybe revisit Gryph's  idea fully cover top of carb. If while still idelling maybe you can hear where air enters. 

Exhaust blowing and Sucking or blowing?

Coolant full?
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline JPaganel

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  • Posts: 184
Re: Bringing K75 back from the dead.
« Reply #43 on: May 14, 2019, 12:11:58 PM »
Quote from: Sopp on May 14, 2019, 01:40:48 AM
Air has to be getting in somehow. Can’t rev like that without lots of air and fuel. Even if I’m new to BMWs, all engines are still just air pumps with combustion.  All the same principles apply.

Exactly.

Not knowing the extent of fire damage to injectors it's hard to say, but even in normal operation o-rings can harden and leak air.
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  • Minnesnowta
  • 1986 K100RT, 1996 R1100RS

Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #44 on: May 14, 2019, 03:40:34 PM »
+1
You have six,  need six,  but three good might do.  Many cars have the same o rings.

Maybe bolt the fuel rail back on too so they are pressed in.
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Martin

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Re: Bringing K75 back from the dead.
« Reply #45 on: May 14, 2019, 03:48:17 PM »
+1 you need to clamp the injectors down with the fuel rail and new "O" rings to eliminate any leaks.
Regards Martin.

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  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline Sopp

  • Motobrick Curious
  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #46 on: May 14, 2019, 10:54:21 PM »
Do the injectors just pull out?  I didn’t want to break anything so I left them in for now.  I did manage to put my back out so that ended working on it for today.  I thought vacuum would hold them in so I didn’t create anything to hold them in.  That will be easy to build.

Sopp
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Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #47 on: May 14, 2019, 11:00:52 PM »
Yep,  they do.

You can get free workshop manuals from this site,  and an actual book will help too.
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)

Offline Sopp

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  • Posts: 34
Re: Bringing K75 back from the dead.
« Reply #48 on: May 15, 2019, 08:53:07 PM »
Pulled the injectors and replaced the o-rings today, that was all my back would let me do.  Everything looked good, nothing obvious. Put a little permeated behind the o-rings. Made a bracket to hold the injectors in place.  When doing this I noticed some “ smoke “ on the intake manifold right above the injectors.  That happened once when it backfired so there must be some sort of hole. Will dig into that tomorrow.

Sopp

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Offline daveson

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Re: Bringing K75 back from the dead.
« Reply #49 on: May 15, 2019, 10:53:12 PM »
The source of the smoke when it backfired was likely the injector holes since the injectors were unrestrained. It is possibly the source this time too,  if your bracket isn't pressing the injectors in with enough force.
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  • Victoria, Australia
  • Current;'85 K100RT~100,000km; four other bricks. Past; 1500 Vulcan, V Star 650, KLX 250(dirt bike) TT250(dirt bike)
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