Fuel leak

FreyZI · 1 Fuel leak Sat Apr 07, 2018 3:52 am

FreyZI

Silver member

Number of posts : 74

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

FreyZI · 2 Re: Fuel leak Sat Apr 07, 2018 3:53 am

FreyZI

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Number of posts : 74

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

charlie99 · 3 Re: Fuel leak Sat Apr 07, 2018 4:00 am

charlie99

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Number of posts : 11701

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

club_c · 4 Re: Fuel leak Sat Apr 07, 2018 8:59 pm

club_c

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Number of posts : 1050

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.

MartinW · 5 Re: Fuel leak Sat Apr 07, 2018 11:54 pm

MartinW

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Number of posts : 3014

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.

FreyZI · 6 Re: Fuel leak Sun Apr 08, 2018 1:08 am

FreyZI

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Number of posts : 74

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?

club_c · 7 Re: Fuel leak Sun Apr 08, 2018 1:12 am

club_c

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Number of posts : 1050

I used an alternative.

Dai · 8 Re: Fuel leak Sun Apr 08, 2018 2:06 am

Dai

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Number of posts : 5720

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.

MartinW · 9 Re: Fuel leak Sun Apr 08, 2018 6:04 am

MartinW

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Number of posts : 3014

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.

glennpm · 10 Re: Fuel leak Sun Apr 08, 2018 4:16 pm

glennpm

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Number of posts : 151

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.

FreyZI · 11 Re: Fuel leak Sun Apr 08, 2018 9:48 pm

FreyZI

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Number of posts : 74

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.

92KK 84WW Olaf · 12 Re: Fuel leak Sun Apr 08, 2018 9:52 pm

92KK 84WW Olaf

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Number of posts : 7967

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.

Dai · 13 Re: Fuel leak Mon Apr 09, 2018 2:09 am

Dai

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Number of posts : 5720

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.

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1 Fuel leak Sat Apr 07, 2018 3:52 am

FreyZI

2 Re: Fuel leak Sat Apr 07, 2018 3:53 am

FreyZI

3 Re: Fuel leak Sat Apr 07, 2018 4:00 am

charlie99

4 Re: Fuel leak Sat Apr 07, 2018 8:59 pm

club_c

5 Re: Fuel leak Sat Apr 07, 2018 11:54 pm

MartinW

6 Re: Fuel leak Sun Apr 08, 2018 1:08 am

FreyZI

7 Re: Fuel leak Sun Apr 08, 2018 1:12 am

club_c

8 Re: Fuel leak Sun Apr 08, 2018 2:06 am

Dai

9 Re: Fuel leak Sun Apr 08, 2018 6:04 am

MartinW

10 Re: Fuel leak Sun Apr 08, 2018 4:16 pm

glennpm

11 Re: Fuel leak Sun Apr 08, 2018 9:48 pm

FreyZI

12 Re: Fuel leak Sun Apr 08, 2018 9:52 pm

92KK 84WW Olaf

13 Re: Fuel leak Mon Apr 09, 2018 2:09 am

Dai

14 Re: Fuel leak

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