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K100-forum.com » Technical, repair and troubleshooting » Engine and transmission » Fuel leak

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1Back to top Go down   Fuel leak Empty Fuel leak Fri Apr 06, 2018 10:52 pm

FreyZI

FreyZI
Silver member
Silver member
So, after I got the bike put back together in the fall and started it up, it ran for a couple minutes and then slowly lost power before cutting out.  I noticed that there was a substantial pool of gasoline in the webs on the top of the engine, beneath the airbox.  Seems most likely to come from some point in the fuel return lines or FPR, as a fine spray.  Guess I'm going to have to pull the throttle bottle assembly to get back there and check hoses, connections, and the FPR ... unless y'all have some advice.

Cheers,

Frey

    

2Back to top Go down   Fuel leak Empty Re: Fuel leak Fri Apr 06, 2018 10:53 pm

FreyZI

FreyZI
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Silver member
BTW, did anybody ever move the FPR to make it accessible?

    

3Back to top Go down   Fuel leak Empty Re: Fuel leak Fri Apr 06, 2018 11:00 pm

charlie99

charlie99
VIP
VIP
just remove the bottom of the airbox , its a struggle without removing the top , the top can be moved to make access though , just undo the hose clamp that mates to the plenum


2 x 8mm bolts hex head of corse in the bottom of the airbox

tip, glue the washers on the bottom of the airbox to engine rubber dampers in place before trying to reassemble


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

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

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

1987 k100rs ########   "Red"  - (red sports rs TWB style )

1989 K100rt #009637   "Black Betty"  (naked rt ala Nigel )
    

4Back to top Go down   Fuel leak Empty Re: Fuel leak Sat Apr 07, 2018 3:59 pm

club_c

club_c
Life time member
Life time member
I had a similar issue last year. Fuel return line had split.  Regardless of the solution change both fuel lines while you’re in there.


__________________________________________________
"There's never enough time to do it right, but there's always time to do it over."

1988 K100RS SE VIN 01477554
    

5Back to top Go down   Fuel leak Empty Re: Fuel leak Sat Apr 07, 2018 6:54 pm

MartinW

MartinW
Life time member
Life time member
If you can get them it is advisable to use the proper EFI type hose clamps, the ones with the nut and bolt. The worm drive type clamps when used in the tank tend to cause premature delamination. And I've also had a couple let go while in use, after working fine for near 12 months. Possibly due to being overtightened at some stage. The quality on some of the worm drive types are extremely variable. If you do have to use them it is advisable to go for a good brand and avoid the cheap ones.
Regards Martin.


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K75s Hybrid
    

6Back to top Go down   Fuel leak Empty Re: Fuel leak Sat Apr 07, 2018 8:08 pm

FreyZI

FreyZI
Silver member
Silver member
Good news -- leak found.  The return hose after the FPR had a couple pin-hole leaks just proximal to the tank fitting.  I guess it stands to reason that it would be there, as that's the connection most likely to be fiddled with, and indeed I have had the tank off several times.  So, now that I need a new hose, do I need to shell out the $32 for the BMW S-shaped hose or can I make do with an alternative?

    

7Back to top Go down   Fuel leak Empty Re: Fuel leak Sat Apr 07, 2018 8:12 pm

club_c

club_c
Life time member
Life time member
I used an alternative.


__________________________________________________
"There's never enough time to do it right, but there's always time to do it over."

1988 K100RS SE VIN 01477554
    

8Back to top Go down   Fuel leak Empty Re: Fuel leak Sat Apr 07, 2018 9:06 pm

Dai

Dai
Life time member
Life time member
Be careful - the forward hose is 6mm ID and the rear hose is 7mm ID (thanks, BMW!). 8mm ID will do but you will need a worm drive to get it tight enough. Make both of them a good 50mm longer than standard and you'll find it a lot easier when shifting the tank around.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

9Back to top Go down   Fuel leak Empty Re: Fuel leak Sun Apr 08, 2018 1:04 am

MartinW

MartinW
Life time member
Life time member
The OEM return line has preformed bends. I had trouble with my non OEM hose collapsing where it goes into the tank on 40C days, ran extremely rich and surged. I ended up fixing the collapsing problem by installing a Unicoil over the hose where it goes into the tank. In colder climes it probably won't be a concern.
Regards Martin.
Fuel leak Unicoi12


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K75s Hybrid
    

10Back to top Go down   Fuel leak Empty Re: Fuel leak Sun Apr 08, 2018 11:16 am

glennpm

glennpm
Silver member
Silver member
With my recent work and taking off the tank several times, I started getting a leak at the supply hose to the fuel rail. I had the correct FI BMW clamp but it was not getting tight enough. I took it off and filed the inner part of the the thread boss to get some increased ID clamping. It worked well. I also put a worm type just above it so now two clamps.

Before all this I noticed I was getting a gas smell in the garage. I suspect this connection was weeping enough to wet the fabric on the hose but not enough to show dripping.

    

11Back to top Go down   Fuel leak Empty Re: Fuel leak Sun Apr 08, 2018 4:48 pm

FreyZI

FreyZI
Silver member
Silver member
On examination, the hose with the leak was not a BMW part -- it was an 8mm and not pre-bent.  I will probably try that again, with the Unicoil, per Martin.

    

12Back to top Go down   Fuel leak Empty Re: Fuel leak Sun Apr 08, 2018 4:52 pm

92KK 84WW Olaf

avatar
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Dai wrote:Be careful - the forward hose is 6mm ID and the rear hose is 7mm ID (thanks, BMW!). 8mm ID will do but you will need a worm drive to get it tight enough. Make both of them a good 50mm longer than standard and you'll find it a lot easier when shifting the tank around.

Dai on both my K100s [84 K100RT and 92 K100LT] its 8mm on all connections, 8mm inside and 13mm outside and I did shell out for BMW line but its not so expensive as they sell a metre length. Not sure on the K1100 yet. I use the R bike worm drive clamps as they are for this fuel line. 6 needed.


__________________________________________________
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 0011157 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 58,200 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.
1983 K100RS 0004449 Odette R100 colours 58,000 miles. Sprint fairing now 59,460 miles

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
    

13Back to top Go down   Fuel leak Empty Re: Fuel leak Sun Apr 08, 2018 9:09 pm

Dai

Dai
Life time member
Life time member
Both my K100s had that odd-sized rear hose. One is '83 and the other (sold) is '86. They both started out as nakeds and have different fuel senders. I have a later tank in the roof, year unknown but post '85 with the resistance sender. Next time I'm up in the roof I'll check the sizes of the fuel spigots. Murphy says they will both be 8mm like yours.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

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