Hello all. Maybe someone out there can help with this anomally.

1987 K100 RT 46k miles.

after a few month hiatus off the road due to a broken clutch cable I took the bike's fairing all off and replaced clutch, throttle, and choke cables. Upon puting the tank back on I found out the tank was leaking underneath from a original rubber "O" ring that had dried up and shrank from no fuel in the tank for months. I Replaced that "O" ring in the sender unit and made sure it was tightend down well by the fuel gauge sender piece. Also replaced the fuel pump vent hose with a new one from a BMW store. Re-installed the tank and added quick dis-connects for the two fuel lines. Re-attached the vent hoses to the underside of the tank. Added 1/4 tank worth of gas. I let that sit for a while and checked for leaks. I only smelled the vapor coming from the vent lines down by the swing arm/ rear brake master cylnder. Thinking that it was due to a near empty tank I decided to fill the tank near full so it would have even less air or vapor in it. I had the same results. After a day of sitting in the garage it has left a strong fuel odor. I have had the bike for over 2 years and it had never created so much fuel smell before. I had pulled some slack on the external vent lines while re-attaching to the underside of the tank maybe it was kinked and now is not. Anyone have any ideas why this could be. Iinstalled the new fuel pump vent hose in the tank exactly like the old one was. I appreciate any advice or help. Also, I saw mention in an older post about the clutch cable nipple holder which has a tendency to slip downward in the lever hole. Mine is doing the same and I am trying to find out how to prevent it. I replaced the clutch cable nipple holder with a new one (the old cable broke in this same area). I have adjusted the cable as directed in this forum and it still slips downward creating an uneven rotation while pulling in the lever. I would like to prevent another broken cable if possible. There was a mention of a fix with a screw to the botom of the lever. Are there any diagrams or directions to do this? Thank you all for your help. James.

When you tested the fuel was it on the centrestand or the sidestand. I ask because if I fill mine rioght up then it will leak out the hose when on the sidestand but not when on the centrestand. Once the level drops a bit then no overflow leak anymore.
Regards,
K-BIKE

I had the bike on the center stand in my garage (level Floor) when I filled the tank. Even today it still had a strong fuel smell after sitting in the garage all night. I am a little concerned as to why and am trying to avoid a flamable situation. I do not believe it is leaking fuel but that it is venting the fuel vapor at an excessive rate. Much more than previously. Any ideas?

you say you have replaced the vent hose recently ....what type of hose was used ?
....it should have had sae 30r10 printed on it somewhere ....i believe this is the lowest grade hose that is rated for full immersion in unleaded fuel and has verry low "permeation " characteristics .

i recently changed my internal hoses twice after i found that the replacement was "wiffy" for want of a better word .

The replacement breather hose was purchased from a BMW dealer and was rated for inside the fuel tank. I will check my receipt and make sure it is the correct rating that you mention. The previous breather hose I had in the tank was a yellow fuel line hose that was rated for immersion but I noticed it had gotten very hard from sitting in the tank and I decided to replace it with the correct hose. Should I blow air into the vent line from outside the bike to remove any fuel that may be trapped in the breather tube?

It could be that there is fuel accumulated in the little trough (for lack of a better word) under the fuel tank, where both the exit the tank.

My bike does not have the trough under the tank. It has a fuel line connected to each metal vent tube and then runs down to exit by the rear brake resevoir. I didnt even know it originally came with a trough until I saw it in a diagram today.

i dont think that blowing air in is productive ....after all it is supposed to be a vent ...ie: allowing for release of internal presures or allowing air in durring tank exansion/fuel level decrease (equalization)

what im suggesting is that some fuel hoses allow the vapours to pass through the wall of the tube at a higher rate and there is hose rated for full immersion in fuel... nothing more .

this could be more an issue in the high presure lines going to and from the fuel rail , where even after switch off, vapours are released .
i have read that sae 30r9 ( not immersed fully in fuel) is suitable for those lines with less permeation in comparison to many of the older types of hoses that were fitted years ago (pre unleaded fuel) and the new chemical components and additives to the fuel we use today bleed through that old hose readilly.


what i would suggest though is not to park the bike with a absolutly full tank of fuel indoors, dont forget the vent tubing itself is inside the tank and is only slightly higher than the top of the filler , if the fuel level is high there will possibly be more oportunity for some release of fuel/fuel vapors, durring expansion and contraction from temperature changes.

but in the end ...maybe having new fuel in the tank and unkinking the drain line has highlighted the issue

ah! just saw that you dont have the "collector" under the tank ...could the syphoning action of the tube be contributing ?

I can remove fuel from the tank and see if there is a difference, but it smelled strong enough with only a quarter tank in it earlier and I thought it was due to the large amount of vapor in the tank. If the new fuel rated vent hose is not the isssue is it possible that fuel is trapped in this hose and thus creating the smell? I never had this problem with the old vent hose. the fuel smell deffinitley seems to be coming from the end of the vent hose by the rear brake resevoir. If I put a plug in the line I could rule out that being the culprit right? Or should I put the old vent hose back in the tank and see if the problem replicates itself? Trial and error I am afraid. I am not keen on having the bike in the garage closed up with a vapor leak like this. Correct me if I am wrong but the vent line to the fuel pump should not have fuel in it right? It should just be air right? Thanks.

Possible small gas leak from the return hose behind the throttle bodies? You should not have a noticable gas smell from the vent hoses, is the vent under the gas cap clogged which will cause the tank to develope excessive pressure?

no it will have fuel in it up to the level of the rest ...+ or minus the amount of presure trying to get in or out ....what i think is happening is that the tank will shrink after switch off ....pushing fuel/vapor out ... what im thinking is that the rubber tube connected to the vent is syphoning more fuel because it has gravity so to speak ...the ideal is to reinstall the collector ....that way there is no fall involved and the residual left in the pipe will vent properly ,,,im thinking the kink in the line before masked the effect

10 cents from a silly old fart

I'm not sure I understand your answer, the top vent under the cap is a aluminum tube that vents directly from the top of the tank to the outside(bottom of the tank), it has no fuel in it.

there is 2 vents at the bottom of the tank chris ,,,,the filler hole top of the tank gasket area (straight through) i guess that should be called a drain .
the second comes from the filter basket on the fuel pump (goes to top of tank via rubber hose then to the bottom of the tank in metal line)

they both sit next to each other at the bottom of the tank and usually there is a small cup which collects the overflow etc, a pipe runs from that cup to near the swingarm/drive area to dump the contents .....well thats on models up to 89 i think
i think i saw a mod for californian models that does some thing different

1987k100rt has no collector but pipes attached directly to those "outlets " whilst it would be ok for the drain im not so sure about the vent ......as it may "hold" excess fuel and vapors in the length of the pipe

i still think that many of us have smelled that fuel smell after stopping and may be quite normal.
i just think that making it back to spec might be a sensible idea .

also, all fuel lines are new inside and outside the bike. Correct pressure rated fuel lines. No detected leaks outside of the tank, Just the vapor smell I mentioned before. I am thinking I may have unkinked the vent line going to the swingarm thus creating an unbalance in venting. I will try the collector and put it back to original spec and see what happens. always an adventure on and off the road with this bike!

The collector is a new thing to me, none of my tanks has one(85-92-94) just straight vent tubes from the bottom of the tanks going to the swing arm area.

oh!! mines an 86 and still has it ...oh well as i said... it may be normal

but obviously somethings changed for our friend .

After I installed my higher windscreen screen I can smell fuel when cruising after I have just filled up. It my explain my erratic behaviour.
Hope you sort it crish8846 it is disconcerting.
RT

chrish8846 wrote:The collector is a new thing to me, none of my tanks has one(85-92-94) just straight vent tubes from the bottom of the tanks going to the swing arm area.

Due to emission laws, this is different on US bikes. But you should have a collector on the `85,
but if it`s an Californian model I`m not shure of that either.
On the `92 and `94, the breather normally ends in the crankcase on US models.

Inge K.

Could you have a leak in the tank? The usual location is underneath the fuel pump location, along the seam.
Re the collector, have a look with your VIN number in REALOEM to see what was original.

Went for a ride last night to check out new clucth, and throttle cables. Everything checked out ok. Put the bike up in the garage to cool overnight. Still have the vapor smell in the garage this morning. As far as I can tell there are no cracks in the tank, the smell does not come from the tank but from the vent hose area by the swingarm. Should have the correct collector that is missing in the next week. Will try that and see what happens. It was only a $3.00 part so maybe this could be a cheap fix for me. Thank you all for your help. By the way does anyone have a reference or diagrams concerning the Clutch cable nipple holder fix? This is to keep to keep gravity from pulling the nipple holder down and creating an un even rotation while pulling in the clutch. Trying to keep the new clutch cable strain free. Thanks

Hi there 1987k100rt. Where did you source the collector from? By bike has the hoses attached to the tank and it's a pain having to try and put them back on every time I move the tank.

Hello Geordnz, I found the collector at Max BMW at their Conneticut location USA. They may have some more in stock. Only cost around $3.00 US. I agree, it is a royal pain trying to remove the tank and the rubber lines from underneath. Even harder trying to get them on while installing the tank. Funny how I did not know the collector even existed until I looked around on this forum. Somewhere along the line it either broke off or was discarded is my guess. I will let you all know how it works when I get it installed.

Great, thanks for that. I believe the early k's did not come with the collector.

OK, sorry for the delay but here is my update on the fuel vapor smell from my bike. The smell has subsided over the last several months. After using the bike and putting it up in the garage I believe the Fuel cap rubber gasket seal and rubber cap seal had dried out due to lack of fuel in the tank for at least 3 months. The seals have "re-sealed" keeping air out and fuel vapor in. That does not account for the vapor smell down by the vent hoses but all I can say is that the smell is gone. Thank you for all the help and expertise. I appreciate it.

Just and update about the fuel collector. I installed it quite easily after lifting the tank and removing the two fuel vent lines. The collector fits right in place under the two drains under the rear right side of the tank. I now only need one fuel line going down to the swingarm. Seems as though the explanation for the strong fuel smell was due to the tank seals not sealing properly due to not being exposed to fuel for over three months. I have not had any problems since. Thanks again for your help.