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torp
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Bedford, England
Joined: 05/25/2010
Posts: 7

Here's a strange one...
When on tickover I get black liquid dripping from the brass "breather" plug on the carb.
When riding the bike it stops dripping but I get a very spluttery ride.
Why is the liquid black? It can't be engine oil?
I think the problem is to do with the carb flooding as I have tested the ignition system.

Peter
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VBMWMO #8076
Australia
Joined: 03/04/2007
Posts: 133
That is different, given it's

That is different, given it's a "closed system" it can only be contaminated fuel? Is it possible that the fuel is mixing with a very old deteriorated fuel hose hence the "black" or possibly a reseal solution within the fuel tank. I would start by inspecting then flushing the entire fuel system.

__________________

R42, R12, R51/3, R69S

R68
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Joined: 08/20/2008
Posts: 466
...response to thopp with black gasoline...

...Your's is a fascinating question. You need to tell us if your working on an R51(1938-41), or on a R51/2-early R51/3, using early 22mm Bings. The first pattern 22mm and 26mm (R68) Bings use the brass vent you seem to be describing, (and also incidentially the 25mm Zundapp Bings!). The R51 initially used the Amal-Fischer carb, and later the Bing-separate float bowl replacement carb. I don't know if the R51 Bing replacement carb used the brass vent thingie. Black gas sounds like very dirty gas, as Peter implies. Drain the tank and start afresh? You might consider removing/cleaning/rebuilding whatever carbs your using. As an interesting historical aside, the Bings used on the later R51 were designed as substitute for the Amal-Fischers, which were British in design, and which required a licensing fee. The contemporaneous government in power in Germany discouraged payment of those fees. If your still using Amal-Fischers, you might consider removing them for safe storage in the safety deposit box at your bank, and replacing with post war R51/2-early R51/3 22 mm Bings, much easier to rebuild and tune....

torp
torp's picture
 Offline
Bedford, England
Joined: 05/25/2010
Posts: 7
Problem Solved. It was caused

Problem Solved.
It was caused by a broken pushrod. This completely screwed up the clearances so the black liquid was unburnt fuel/oil being pushed back out of the cylinder into the carbs.
Took a while to fix but bike now fine!

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