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Topic-icon Carb issues

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11 months 1 day ago - 11 months 1 day ago #121537 by trijonb
Carb issues was created by trijonb
hi guys,

I was wondering whether anyone could assist me with some general carb diagnostics. My KLE500 (dual carb) has stood for 6 months and when i filled it up for a new ride, I got some leaking out of the airbox drain. Taking the airbox out, i noticed some small flow out of the RHS carb jet, pointing to a stuck float valve.

I removed the float bowl and cleaned, yes the float value was gummed and stuck. I did both sides. I did an "air blow" test, and everything seems to seal properly airtight when the floats travel and close.

Putting the assembly back and filling the tank, and trying to restart, it seems that I am still getting some leaking into the airbox, but what "seems" like a large return / overflow leak from a second clear tube which is attached to a common rail which comes off of the back of the carbs, about 3/4 up the carb.

Problem is, I don't know what this tube is and why it would be leaking fuel when i try to start. I've attached a pic, you can see the clear tube in the back.



Trying to start the bike, it seems to flood very easily. Occasionally it kicks into life beautifully and runs for 10 secs, and then dies, like its run out of fuel … ?

The bike is in pretty good nick and clean, the float chambers were not even that gunked up. So i cant imagine there is anything major wrong? I have this tube running directly downwards, through the frame to the road, perhaps it should be pointed up, and run over the airbox so it only drains after a certain fuel height?

I knows its a KLR forum, but you guys are all tech savvy, and I am sure the major components are similar to the KLR carb (actually, its the same, just a single, bigger model on the KLR (Keihin CVK40 x1 (KLR650) vs Keihin CVK34 x2 (KLE500)).

I'd really appreciate any assistance or advice.

Cheers
Jonathan

EDIT: I did not remove / unscrew any of the main or secondary jets since i didnt want to mess with resetting them, I blew carb cleaner through all x4, and all are clear - aerosol blows through easily from both directions.
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11 months 1 day ago #121538 by trijonb
Replied by trijonb on topic Carb issues
UPDATE: So looking at old pictures, it seems this pipe is supposed to run upwards and over the airbox, so having it directed directly downwards was definitely a problem.

I'm still very keen to know what it is / for.

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11 months 1 day ago #121539 by capeklr
Replied by capeklr on topic Carb issues


Problem is, I don't know what this tube is and why it would be leaking fuel when i try to start.


Hi Jonathan,

That is a breather tube for the carbs.
It does not matter if the pipe points up or down.
On the early KLR's it also pointed down, its only on the new shapes that is sits above the
air box.
Petrol should not come out there, there must still be something blocked in those carbs.

"The world is a book and those who do not travel read only one page."
St Augustine
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11 months 1 day ago #121540 by trijonb
Replied by trijonb on topic Carb issues
Hi Cape,

Yis, thanks a lot - I appreciate that. OK, I've moved it over the airbox and am recharging the battery. I gave those things a very good cleaning out (i thought) but maybe 4th time will be a charm.

I must research a little what the breather is actually for (apart from the obvious :) ). Thanks mate.

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11 months 1 day ago #121541 by trijonb
Replied by trijonb on topic Carb issues
For anyone that is interested, this is a good explanation:
the fuel in the bowl is moved by a difference in the air pressure acting on the fuel and the low pressure area caused in the venturie

if you block the vent , the venturie will not be able to suck up the fuel do to the vacuum created in the float bowel

so the engine will slowly die out

so basically you need a port into the float bowl at atmospheric pressure to prevent vacuum locking and allow the fuel to flow up the jets.
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10 months 3 weeks ago #121587 by trijonb
Replied by trijonb on topic Carb issues
Just wanted to give a shout out to Alan @Bobs Motorcycles (Watsonia St, Tygerdal, Cape Town) (083 233 8681) for his help on this. He redid the carbs for me after the above and the bike is running beautifully. I have to say what a great experience, fast, professional, really good work and knowledgeable and willing to share info and advice for free.

I would really recommend him if you need bike assistance or don't have time to do it yourself.
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