13 replies to this topic

[Paulmount]

Hi all

 

BIG HELP NEEDED

 

This has happened on two sets of Carbs on my 1997 TDM 850, petrol coming through the overflow while on idle.

 

Firstly, the second set of Carbs have been ultrasonic cleaned with new floats, float needles in fact everything new.

 

Started first time and ran great until I got home and it started dripping right on the exhaust!!

 

Thinking the float was stuck I took the carbs off but no sign of sticking ???

 

Put it all together and ran fine for 10 minutes then started dripping again !!!

 

Please any idea as it has happened on two sets of carbs now and if it carry’s on the bike could go up in flames either at home or at some traffic lights etc??

 

Hopefully someone has had this problem.

 

Thanks in advance.

[steveearwig]

Probably a daft question but did you also change the needle seats?

[Paulmount]

Hi, yes the whole lot was rebuilt with new. Why you say that, could that cause the problem?

[dablik]

Can you be sure it's the carbs, unusual to happen with 2 different sets, check fuel lines and fuel tap is not leaking.

[Studley Ramrod]

Hope its not a crack in the float bowls where the drain screw goes. Where are you ?

[steveearwig]

Hi, yes the whole lot was rebuilt with new. Why you say that, could that cause the problem?

Experience, I replaced everything else but I still had fuel coming out of the overflow (bike leaks fuel, take it apart, can't find anything, put it back together, take it for a ride, leaking again, take it apart again... keep repeating until you go mad)

 

Btw I don't know about the 4TX but on the 3VD the overflow pipes eject fuel onto the ground via tiny tubes. Chucking it over the exhaust sounds a bit dicey to me...

 

Just a thought - are you still running the original vacuum fuel pump?

[dablik]

I've also had the overflow leaking on 3vd carbs, checked and inspected 2-3 times and on the next check found a tiny speck of crap which was causing the whole issue, or as Studley said a cracked housing where the drain screw can be overtightened, done that easy to do..  Fuel tank not leaking underneath anywhere ??

[PeterGriffin]

Had the same issue after i decided to fit an electric pump...reckon it was too powerful...waiting on a vacuum one now....

[Paulmount]

Hi all.

Answers to the above......

 

Fuel lines and fuel tap is not leaking.

 

No crack in the float bowls where the drain screw goes or any leaks from the tank

 

Fuel leaks down the overflow pipe and ejects fuel onto the ground via tiny tubes. 

 

Vacuum pump

 

based near Manchester

[dablik]

Then the only thing left that could possibly cause a leak down the overflow is shoite in the carbs, most prolly under the float needle.. it's frustrating innit..

 

And it could be miniscule..

Edited by dablik, 03 April 2022 - 08:50 pm.

[Catteeclan]

Float levels set correctly?

[steveearwig]

Fuel leaks down the overflow pipe and ejects fuel onto the ground via tiny tubes.

 

 

Ah, that's a relief. This kind of eliminates anything else other than something amiss in the float chambers.

 

It's probably worth checking the float levels, although this seems unlikely across 2 sets.

 

Same with a piece of, what was it? A piece of shoite, across 2 sets? Hmm. Although I have experience of a bit of crap coming from nowhere, carbs rebuilt (twice...), new fuel lines, tanked cleaned and linered but a piece of old fuel line came from somewhere and jammed a valve in the pump open, causing the bike to run out of fuel on it's first ride (arse).

 

Anyway, you have my sympathies for the endless take to bits, find nothing, put together, it's still f*cked frustration, it took me a year before I gave up and found someone who knew what they were doing to look at it (which didn't work out too well either).

Edited by steveearwig, 04 April 2022 - 08:29 am.

[curlylegend]

 

Ah, that's a relief. This kind of eliminates anything else other than something amiss in the float chambers.

 

It's probably worth checking the float levels, although this seems unlikely across 2 sets.

 

Same with a piece of, what was it? A piece of shoite, across 2 sets? Hmm. Although I have experience of a bit of crap coming from nowhere, carbs rebuilt (twice...), new fuel lines, tanked cleaned and linered but a piece of old fuel line came from somewhere and jammed a valve in the pump open, causing the bike to run out of fuel on it's first ride (arse).

 

Anyway, you have my sympathies for the endless take to bits, find nothing, put together, it's still f*cked frustration, it took me a year before I gave up and found someone who knew what they were doing to look at it (which didn't work out too well either).

 

Just take one float level to be wrong....I speak from bitter experience !

[Mechengine]

Hello All new here,

 

I'm having some similar issues. I have a 92 TDM850 It had been stored for about 10yrs. I took it out started going through the bike fluids etc. I started the beast using a bottle with the tank off and low and behold she came to life. Then she started to bog and misfire I noticed fuel coming from both overflow tubes and turned off the fuel valve. She cleaned up and continued to run perfect. So figured it was time for a carburetor rebuild. I broke them down and did a complete rebuild all new seals, o-rings, jets, needles, diaphragms and needle valves. The kit did not include the seats. Reinstalled the carbs she fired up and started leaking fuel again from the overflow tubes. I have checked, set, reset retested still leaks. I have replaced the o-ring on the seat checked for a cracked bowls and all is good. In over 40 years of working motorcycles I have never been stumped like this. I have removed the float assembly connected it to a syringe via a hose and under pressure tested the needle and seat and it will flow and seal even against some pretty good pressure. It doesn't appear to be the needle and seat and I have float level about 2mm under the recommended levels and it still leaks. I can't find any cracks in the bodies or the bowls but both carbs still pour fuel even when I run them on gravity and don't use the pump which is still working. I know I dumped a lot or info but does anyone see anything I'm missing? I apologize if this is in the wrong place but I was having a problem getting a new post started. Any thoughts would be appreciated.