8 replies to this topic

[Monstrosix]

Replaced the needle on the left hand carb but still leaking fuel from the overflow.

I have read about setting the float height with a clear tube but it seems simpler to measure the height with the float chamber base removed. Does anyone know what height they should be set at or am I barking up the wrong tree and using the wrong method? 

I can only think that any other cause could be the overflow pipe itself, but it seemed fine when I dismantled it.

Any thoughts, help or advice always appreciated   

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[Studley Ramrod]

You can check the fuel levels without removing the carbs using the clear tube method, you just need an auxilliary fuel supply.  Once the battery and battery box is removed you can access the drain screws and fit the tube.

 

It might be that adjustment of the float bowl tang is required to lower the fuel level, or it might be that the drain screw has been overtightened and caused the float bowl to crack, causing a leak.

 

Measuring the float height requires removal of the carbs as you need to have the carbs upsidedown in order to measure.

[steve27bha]

As Studley has said, the tube method is great for checking the current fuel height, but you need the carbs off to adjust them.

Once that has been done use the tube again on the bench to check that the setting is correct before installing (and finding it is wrong....).

Just be grateful you have only two carbs - I learnt this stuff on a 4-carb bike that required considerable dismantling just to get the carbs off.

Also, check that the valve is not held open by crud from the tank/lines. And protect the work you have done with a clean/new fuel filter.

[dapleb]

There is good info on the factory pro site aboot setting fuel levels. Beware floats are diff heights. Don't measure from diamond one.

Think I set mine at 13mm but can't check at the mo.

[dablik]

In the past i have found a tiny spot of dirt in the float chamber prevented the float from closing and resulting in a leak, after a meticulous clean

[Monstrosix]

Lots of suggestions for help which is much appreciated.
I have cleaned as much as Ive dismantled so far but I guess a tiny/ missed amount of crud could cause the problems I have.
Will check float heights next I think.
Much appreciated folks, thank you 🙏

[Jamesb]

Hi guys, recently bought a 97 TDM 850 with 20k that had been standing for 10 years, as such fuel in the carbs was varnish. Have just installed a full keystar kit. Now time to set the fuel height. As the carbs are off the bike, I thought to do the tilt measure method and start with float height. But I have two questions. 1. As the floats are not the same size on both sides of the arm, which one do I measure? And, 2. What should the float height be? I know fuel level is 15.8-16.8 but I can't find any info on the float height itself. Any help appreciated. Cheers

[Studley Ramrod]

Hi and welcome.

 

Have a look here, scroll to bottom of page

 

http://www.factorypr..._procedure.html

 

All you need to know about tuning CV carbs here

 

http://www.factorypr...pm_engines.html

 

 

[Mechengine]

Hello All,

 

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 I 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.