The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Dizerens5 on March 12, 2012, 03:48:50 PM
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My 79 has suddenly got a bad fuel leak from the right-hand carb. At first I thought of a split fuel hose but that's all dry. Anyway it only leaks with the bike on the side stand -- get it vertical and the leak stops. I guess the problem is with the float, maybe rotted out with all the chemical junk they put in our fuel these days. So I'm thinking of a bit of modernisation of both flat-tops. What's the experts view -- just replace floats and float needles, or take the full float-bowl conversion, still available (but expensive)? Any any ideas about how to shift the float pivot pins? Mine seem well stuck. Haynes says: use pliers, but that does not seem possible. I don't even know whether to push from the splined end or the other end, anyway. And what kind of drift to use, on such a tiny part? Thanks!
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Corroded carbs was the biggest problem and first thing I went through with my bike when I got it. Thing is I just got over it. Rebuild them. It's easier than you think and you'll feel better knowing they're clean. The kit I got just came with the o'rings for the jets and the float gasket. While it helped it didn't do the job. I decided to get the float needles and that made my bike run funny (i guess it had been tuned to compensate for the float clips being adjusted to the old worn out needles.) I decided to just go for an entire overhaul. Diaphrams, and float bowls too. Worked! now my bike is happy and I am too.
If I had just done the job right the first time I wouldn't have had to rebuild my carbs 3 times.
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You still may have a carb problem, but these bikes were not meant to be kept on the side stand .
If you still want to go into the carbs, the float pin comes out from the end that has serrations .
If the pin won't come out, you may need something like a small pin punch to get the pin serrations free of the aluminum 'leg '.
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Any any ideas about how to shift the float pivot pins? Mine seem well stuck. Haynes says: use pliers, but that does not seem possible. I don't even know whether to push from the splined end or the other end, anyway. And what kind of drift to use, on such a tiny part? Thanks!
Easiest way to remember is to say the splined end comes out first so you push from the other end. Pliers can be used to get the pin moving but only if the non splined end protrudes a little from the lug on that side. You can then use the pliers between the end of the pin and the other side of the lug. It will only move fraction but if it gets it moving the battle is nearly won and without putting any bending stress on the lug. The pin can then usually be tapped out gently with a thin punch.
If the pin is still really stuck and you are committed to removing it, I would probably devise a way of destroying the floats to get them out of the way. I would then make up an accurately fitting spacer to fit between the two lugs and provide a solid support to the other side so that the pin could be punched out without subjecting them to excessive bending stress.
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Breaking it down Barney-style... Do not do anything that might put stress, re: breaking pressures, on the pot metal legs holding the float pivot pin.
You may have a bodged float needle. These rascals have a firm rubber contact point where they meet the needle jet fixture. Easily seen by removing the needle... after getting the float removed.
Fab a simple jig to support both float legs and then you can gently tap the pin out. The splined end comes out first. After that, you're home free.
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And remember, any time you are parking for a while, shut your petcock off as you are arriving at your destination, say 10 - 15 seconds away.
This lowers the level of fuel standing in the bowls.
But these bikes are old enough that things like the fuel system need refurbishment if it hasn't already been done. You might consider doing the petcock, as well. I know mine needs it. It is still original. :-[
And I would stick with stock floats, but plan on replacing them every 5 years or so, if it comes to that.
You will get real good at it, and it will keep the pins happy!
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I see no reason for a rebuild just because it's leaking. That's almost as bad as saying "since the valves are making noise, I probably should get the heads rebuilt". Makes just about as much sense!
The fuel is leaking out, and there are only a couple of reasons that would happen. You'll need to look close at the parts and inspect them well. You'll find either a compromised cork gasket, fuel level too high, gouged sealing surfaces, or perhaps a float bowl vent tube with pinholes.
Get back to us with your findings, especially if it's none of the above.
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I see no reason for a rebuild just because it's leaking. That's almost as bad as saying "since the valves are making noise, I probably should get the heads rebuilt". Makes just about as much sense!
The fuel is leaking out, and there are only a couple of reasons that would happen. You'll need to look close at the parts and inspect them well. You'll find either a compromised cork gasket, fuel level too high, gouged sealing surfaces, or perhaps a float bowl vent tube with pinholes.
Get back to us with your findings, especially if it's none of the above.
Agreed.
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Thanks, this has really got me on the right track. I'm ordering new floats plus needles and gaskets. Just to be clear, I do always shut off the fuel on stopping. The leak appeared when turning it on to start up, with bike on side stand. It's on that stand only while I open or lock the garage door. Interesting: when I got the 79 about 3 years ago I discovered that there were no float bowl gaskets. When I tried to instal them I discovered why -- it was impossible to snap the spring clip shut (at least without using superman force). But there was never a leak until the other day. Another reason why I suspected the float.
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when I got the 79 about 3 years ago I discovered that there were no float bowl gaskets.
That's very strange. I would have thought without a gasket fuel would continually slop out at the front of the float bowl.
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I too find that odd. I've never heard of bings with no bowl gaskets!
If they're too tight, bend the bail a bit to remove some of the pressure.
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I found it strange as well! Possibly there may have been a bit of fuel mist when riding? But I never noticed, there was no fuel smell and consumption was fairly normal...if a bit high, I must say. But the leak which appeared the other day was a big one, about as fast as a drip can get without becoming a steady flow. Straight on to the exhaust. Made me wonder just how hot metal has to get to ignite fuel or vapour! But with the bike vertical it stopped completely, every time. Sometimes I think Einstein would have had some trouble.
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While you mentioned fuel dripping onto a hot exhaust system, a bit off topic though .
When you remove the fuel cap, you'll see a drain hole in next to the fueling opening .
On the bottom side of the tank, there is a short piece of tubing that comes out of the tank, if you don't have a short length of tubing on it, if you get an overflow situation while refueling, your dumping fuel on a hot engine .
I only let that happen once, that was on my second fill up after getting the bike .