BMW K bikes (Bricks)

You are not connected. Please login or register

View previous topic View next topic Go down  Message [Page 1 of 1]


1Back to top Go down   Tank vacuum Empty Tank vacuum Mon Apr 13, 2015 6:58 pm

desperado

desperado
active member
active member
Hey guys

I'm new to the K bikes and actually have never owned anything injected before. I'm on an 85 K100RS and I have an intermittent loss of power that feels like I'm running out of fuel. I notice it mostly in higher gears. At first I thought it could be a clogged injector problem but I've run Techron injector cleaner through. After that I noticed that when I shut the bike off, I can hear air getting sucked into the tank via the gas cap. When I open the gas tank, I can hear a rush of air to equalize the pressure. Is this normal? Is my cap not venting properly? It seems to me that my pump is fighting this vacuum pressure and could be causing my issue. If that isn't it, I'm assuming I need to pull the filter and maybe the pump and go through it. The tank is incredibly clean, but maybe there is some clogging in the lines. Any thoughts?


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

2Back to top Go down   Tank vacuum Empty Re: Tank vacuum Mon Apr 13, 2015 7:34 pm

brickrider

brickrider
Life time member
Life time member
Desperado, when you open the cap to the fuel tank, you can see a small hole at the 9:00 position that vents the tank. Be sure your cap does not obstruct that vent hole.  The cap can be installed incorrectly.  By that I mean 180 degrees wrong.  The cap's hinge should be near the rider, not near the controls of the bike.

    

3Back to top Go down   Tank vacuum Empty Re: Tank vacuum Mon Apr 13, 2015 7:37 pm

desperado

desperado
active member
active member
@brickrider wrote:Desperado, when you open the cap to the fuel tank, you can see a small hole at the 9:00 position that vents the tank. Be sure your cap does not obstruct that vent hole.  The cap can be installed incorrectly.  By that I mean 180 degrees wrong.  The cap's hinge should be near the rider, not near the controls of the bike.

thanks for the response, brickrider. the cap is installed correctly. do you think i should remove the cap and see if it's clogged. any tips for that?


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

4Back to top Go down   Tank vacuum Empty Re: Tank vacuum Mon Apr 13, 2015 8:04 pm

desperado

desperado
active member
active member
so I fired up my air compressor to see if the venting line was clogged. pretty sure it was. after putting some pressure through it, i was able to hear air coming out of the underside of the tank on the right side. could this have cleared my issue up? i'll ride over the next few days and let you know of any updates i have.


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

5Back to top Go down   Tank vacuum Empty Re: Tank vacuum Mon Apr 13, 2015 8:20 pm

92KK 84WW Olaf

avatar
Life time member
Life time member
As far as I know the vent comes out on the right side rear of the tank..........so you should be sorted.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 39.885miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

6Back to top Go down   Tank vacuum Empty Re: Tank vacuum Mon Apr 13, 2015 9:59 pm

Holister

Holister
Life time member
Life time member
There should be a collection cup under that outlet as well with a drain tube to the rear of the foot peg.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Tank vacuum Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

7Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 12:47 am

robmack

robmack
Life time member
Life time member
@brickrider wrote:Desperado, when you open the cap to the fuel tank, you can see a small hole at the 9:00 position that vents the tank. Be sure your cap does not obstruct that vent hole.  The cap can be installed incorrectly.  By that I mean 180 degrees wrong.  The cap's hinge should be near the rider, not near the controls of the bike.
Brickrider, That hole you describe is not for venting the tank. It's purpose is to drain rain water that may collect around the cap, so that the water does not contaminate the fuel should the fuel cap be opened after a shower.

The vent for the tank is just under the cap, inside the tank. You can feel the tube inside the tank at the 12:00 position. Both the vent tube and drain tube terminate at the lower right underside of the tank.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

8Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 11:51 am

brickrider

brickrider
Life time member
Life time member
Okay, I stand corrected.  Thanks. My apologies for misleading you, Desperado.  I hope all is well with your new-to-you K-bike now that you've verified the vent is open (in the lower right underside of the tank!).

    

9Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 2:02 pm

desperado

desperado
active member
active member
@robmack wrote:
Brickrider,  That hole you describe is not for venting the tank.  It's purpose is to drain rain water that may collect around the cap, so that the water does not contaminate the fuel should the fuel cap be opened after a shower.

The vent for the tank is just under the cap, inside the tank.  You can feel the tube inside the tank at the 12:00 position.  Both the vent tube and drain tube terminate at the lower right underside of the tank.

thanks, robmack.

there seems to be some confusion on that drain hole. i've read it both ways across a few different sources. i'm not finding a tube at 12:00, but there is one at 6:00. is that the one? any tips for cleaning that out? it looks like i might need to take the tank off. do one of the overflow hoses connect to it?


__________________________________________________
1985 K100RS
Los Angeles, Calif.
    

10Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 5:13 pm

rosskko

rosskko
VIP
VIP
Pop the tank off. Two hoses, one power plug, lift the back, slide it back a few inches and off it comes.
Access to the overflow pipes will be obvious on the bottom.Blow a bit of air into them. I would probably do that quite gently, just in case.

There are excellent photos of the inside of the tank somewhere on here. One member cut his in half and posted the shots.
Pretty sure Robmack is right on the location of the overflow inside the tank


__________________________________________________
1986 K100RT VIN 0093801K100RT with summer fairing for a northern visitor

Basic/2 6308802K100CJ  05/1988

K1100RS 0194321
    

11Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 5:49 pm

sidecar paul

sidecar paul
Life time member
Life time member
Tank vacuum Sam_0710
This is the vent pipe.

Paul.


__________________________________________________
'84 K100RS (0014643) (owned since '85), 86 K100RS (0018891) with Martello sidecar (built as an outfit in '88),
'51 Vincent (since '67),'72 Montesa Cota (from new), '87 Honda RS125R NF4 (bought 2015) 
....No CARS never ever!
    

12Back to top Go down   Tank vacuum Empty Re: Tank vacuum Tue Apr 14, 2015 6:52 pm

rosskko

rosskko
VIP
VIP
Inside the tank

So the two pipes at the bottom are the overflow and drain from the cap.


__________________________________________________
1986 K100RT VIN 0093801K100RT with summer fairing for a northern visitor

Basic/2 6308802K100CJ  05/1988

K1100RS 0194321
    

13Back to top Go down   Tank vacuum Empty Re: Tank vacuum Wed Apr 15, 2015 5:05 am

TacKler

TacKler
Life time member
Life time member
Sounds like when fuel is being pumped from the tank into the engine, there is no equalising of pressure in the fuel tank.  Therefore the air you hear rushing into the tank is the tank trying to equalise the pressure to ambient.  That leads me to think it is a blocked vent. 

No problems with insects?  I have a problem with b*stard wasps building their mud food sacs everywhere and underneath motorcycles is a common target.  Mad


__________________________________________________
Red 1991 K75S
    

14Back to top Go down   Tank vacuum Empty Re: Tank vacuum Wed Apr 15, 2015 5:23 am

charlie99

charlie99
VIP
VIP
@robmack wrote:
@brickrider wrote:Desperado, when you open the cap to the fuel tank, you can see a small hole at the 9:00 position that vents the tank. Be sure your cap does not obstruct that vent hole.  The cap can be installed incorrectly.  By that I mean 180 degrees wrong.  The cap's hinge should be near the rider, not near the controls of the bike.
Brickrider,  That hole you describe is not for venting the tank.  It's purpose is to drain rain water that may collect around the cap, so that the water does not contaminate the fuel should the fuel cap be opened after a shower.

The vent for the tank is just under the cap, inside the tank.  You can feel the tube inside the tank at the 12:00 position.  Both the vent tube and drain tube terminate at the lower right underside of the tank.
on some models (well on mine anyhow )  this vent is attached to the filter basket around the bottom of the fuel pump by a piece of rubber hose ..( which usually deteriorates ..sitting in the fuel )

Tank vacuum Fuel_t10


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OTank vacuum Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

15Back to top Go down   Tank vacuum Empty Re: Tank vacuum Wed Apr 15, 2015 5:12 pm

japuentes

japuentes
Life time member
Life time member
Hi there, there are four pipe niples on the tank, two front left are fuel supply and return. The other two more or less rear right are one for draining water around the cap an the other to collect fuel vapor and vent it, on california models to the crankcase, and on the others to atmosphere.
As far as I know there is a builtin check valve in the fuel cap, this allows  air to enter the tank, and avoids fuel vapor leaks up to a pressure of 2.9psi.
Hope this helps
Best regards
JAP


__________________________________________________
Tank vacuum 2854237993 1988 K100RS SE/ABS
    

View previous topic View next topic Back to top  Message [Page 1 of 1]

Permissions in this forum:
You cannot reply to topics in this forum