need advice: fuel leak 77 r100s

Started my bike after months of sitting idle and after just getting it started and turning off the choke, the engine sounded nice and smooth. Then I noticed some dripping from the oil pan underneath. I know the oil pan gasket needs changed but i also saw some clear fluid dripping and it is definitely fuel. Where is it leaking from? Any advice how to figure out and fix the problem is appreciated. Here is a link to see a couple of pics. The first two black and white pictures are of the 77R100s i'm talking about. Thanks for the help. The one pic with white circle and line drawn on it is to show where the fuel was coming down from and dripping.


https://www.photo.net/my/portfolio/

Your photo link isn't working for me. If it's not dripping out of either of your carbs or the tank itself, it could be leaking out of the fuel line that runs through the airbox, above the transmission.

https://www.photo.net/photo/18397667/


https://www.photo.net/photo/18397666/untitled

Can you see a wet trail from the circled area up the side of the case? It's obviously the low point, and if it's fuel, seems like it would have to be running down the side from the carbs or possibly from the tanks somewhere.

20774 said:

Can you see a wet trail from the circled area up the side of the case? It's obviously the low point, and if it's fuel, seems like it would have to be running down the side from the carbs or possibly from the tanks somewhere.

Click to expand...

Yes thats exactly what I see: wet trail down to the low point. Does not seem to be coming from the carbs. I have never taken the fuel system apart before so if there are fuel lines inside the airbox I think that would be a very good guess of where it is coming from. What is the easiest way to take this airbox off? The choke is on the left side of the airbox. Here is a pic of the bike:

https://www.photo.net/photo/18318003/untitled

I think you've found a likely leak. There is a cross-over fuel line that goes from the left side to the right side of the bike. You can see it at the T-junction from the lines that come down from each petcock.

To get to that line, you'll need to remove the air cleaner and connections to the clam shell cover. Remove the clamps that hold the black air tubes to each carb...you'll need to loosen the clamps on the head side of the carb to allow move around to get the tubes off. On the left side, you'll see a straight slot screw head that you'll remove...that's a long screw that reaches over to the other side. Then you should be able to pull the left side clam shell off...pull straight out, maybe with a little wiggling. Remove the air filter. When you look in from the left, you'll see the nuts that hold the right side cover on.

You may be able to feed the new line through the small hole in right side clam shell cover without removing it. It will make things easier. Assembly is reverse order.

There are sources for the cloth covered black fuel line. Some prefer to buy locally sourced fuel line...I believe the auto parts fuel line is 1/4" inside diameter whereas the OEM fuel line is 6mm...I think I have that right. Others will have suggestions for your options.

Thank you! That is exactly what I needed. Will let you know how it goes. Will try to get to it later this week.

Very nice bike! You do want to fix that before riding it further, and risk gasoline dripping onto your back tire or blowing onto a hot muffler. While you're at it, just replace all 5 pieces of fuel line---2 from the tank to the crossovers, 2 from the crossover to the carbs, and then the one piece crossover through the airbox. $12 worth of cloth-braided fuel line should keep that beauty flowing fuel to where it belongs for quite awhile.

I found the 1/4" lines to be a loose fit and they better be clamped. 6mm lines are tight and sometimes hard to slip on. The cloth covered line may not fit through the pass-through holes. I went to the BMW car dealer and bought the 6mm unclothed version.

/Guenther

Thanks for all the advice. Will plan to change all the fuel lines as suggested.

done!

Finally got around to changing the fuel lines. Went with Tygon lines. Only $17 for (3ft) enough to replace all the lines with almost a foot to spare. Very easy to install. I was able to feed the center line through the hole in to the airbox over an 18guage wire that I threaded through with an old RC car antenna. Trying to thread the hose through on its own would have been much harder as its flexible and did not want to go straight. These lines are not braided like the originals but Ted Porter at the Beemershop swears by them so I gave it a shot. So far so good.

The Tygon lines have worked well for me, for years.
BR

plexiform said:

Finally got around to changing the fuel lines. So far so good.

Click to expand...

Glad this worked for you. Question, are you sure your bike is a '77? My '77 has a drum rear brake. Discs were standard starting in '78

title says 77. Any other way to confirm this is a 1977?

Plug your 7-digit VIN into here:

http://www.bmw-z1.com/VIN/VINdecode-e.cgi

If the build date is Sep 1976 - Aug 1977, it's a 1977. If Sep 1977 - Aug 1978, it's a 1978.

20774 said:

Plug your 7-digit VIN into here:

http://www.bmw-z1.com/VIN/VINdecode-e.cgi

If the build date is Sep 1976 - Aug 1977, it's a 1977. If Sep 1977 - Aug 1978, it's a 1978.

Click to expand...

Kurt, is that set in stone? I ask as my R100S was mfg 7/77 but original title has it as a 1978, rear drum brakes.

kinterridge -

I'm not sure anything BMW did was cast in stone! But the general rule was that the August the time that the factories changed over for the new model/run. So then September of 1977 to August of 1978 would have been considered 1978 models. Hard to know what really happened when say the /7 models first arrived for 1977. Here's a page that breaks out VINs by month:

http://www.bmbikes.co.uk/chassispages/enginechassis1000.htm

Note that the first R100/7s were made in May 1976 but I'm pretty sure they are really classified as '77 models. So ahead of a new model, they might have ramped up production early in order to be ready for the new model year and hopefully demand.

All that said, titling, build year, and model year aren't necessarily the same thing. I can certainly see when getting a bike registered if the agency doesn't really know the differences, they might take the build date of 1977 and call that a 1977 model. Once it gets titled a certain way, it's probably best just to stick with it. Getting parts is not really an issue...just give them your VIN and that should settle things. My R100/7 is a September 1977 build and it's been titled a 1978 for as long as I've owned it...the previous owner is the one who got the initial registration.

Prior to the /5, I think things were a bit fuzzier...in reality, there were essentially no major changes to the R69S from late 1960 to 1969. That can't be said for the periods of the /5, /6, /7, etc. My R69S was built in the spring of 1968 but has always been titled as a 1969. It wasn't delivered to a German dealer until December 1968 at which time it was deemed a 1969 model. Maybe your 7/77 bike wasn't actually sold until later in 1977?? Do you know the history of the registration?

I agree. It's important to know the MODEL YEAR when looking for parts (or advice) as different states had different title rules back then.

Here is a great brochure website that shows some of the different features, options, paint schemes for the 77-79 bikes.

http://www.omnilex.com/public/bmw78/

Note that each photo can be enlarged by clicking.

Kinterridge- with a drum rear, I would think you have a 77 Model year bike. Are the gauge faces green or white?

Kurt, thanks for the info, I have read and know much of what you've posted, I have always suspected it was in the original title in PA (Pennsylvania) that was wrong. It was a dealer demo that had dealer installed Luftmeister fairing, tall bars with a backset bracket for the bars. The original owner I've known from purchase, after dealer ran it, it was titled to him as a '78 and I think the dealer had it awhile before titling, would be my guess.

mine says production date 1976/07 but title says 1977