Left carb leaking!!!

[Romaz750R]

The problem is, the left carburetor leaks when the bike is on the side step. Gasoline flows through the drain hole (not through the seals). When I put it straight, it stops leaking. It also stops leaking when I close the fuel valve. Float level is correct, all rubber seals (including needle valve seal) are changed. Has anyone seen one of these? Maybe change the float level? Thank you in advance.

[Rene EFE]

Changed/replaced doesn’t automatically mean all is well. 

Also, I know of one example of an actual float leaking and therefor not raising with the fuellevel; something to check as well. 

[Romaz750R]

1 hour ago, Rene EFE said:

Also, I know of one example of an actual float leaking and therefor not raising with the fuellevel; something to check as well. 

I checked all floats for leaks and they are all right. And, as I said, when I put the bike straight, it stops flowing ... so I'm thinking, is tuning another level of the float of the left carburetor would help?

[wsn03]

Needle flost valves - any aftermarket ones you can scrap, they all leak. Buy Mikuini or live with the leaks

 

To test - stick carbs on bench. Half fill remote fuel tank (Demon Tweeks sell them) connected to carbs

Give it 24 hrs. ... dont smoke,.observe fuel all over the bench, tank empty. Needle floats (supplied by your trustworthy aftermarket carbs specialist) are leaking.

Then buy some Makuni (re-mortgage or buy from USA)

 

Edited July 24, 2018 by wsn03
Typo

[Oilyspanner]

I've had several carbs that have caused headaches in the past (and fairly recently) and when all looks like it should work, with the f.valve  shutting off the fuel, but doesn't - this has worked :

Any slight residue on the sides of the valve seat will cause the float needle to snag slightly - the needle valve should be able to move freely, modern fuels are sods for leaving residue. Use a light polish to remove the crud, you know when you've done the job - the run up to the valve seat will be the nice brass colour again. Make sure the float needle is clean too - once done the needle should move freely up and down the valve seat assembly. I normally use a cotton bud to apply the polish (brasso works well), or cotton wrapped on the end of a cocktail stick, you can spin these with your fingers, or use a drill (which is what I use, just be gentle with it).

When the carbs are at an angle, the floats don't exert as much force on the float needle (lop sided force acts on the pivot), so if the needle slightly resists movement, the needle won't shut the fuel off properly.

It's always hard to visualise issues on the net, but doing this has prevented me from doing nasty stuff to the carbs for wasting hours of my time …...

[wsn03]

2 hours ago, Oilyspanner said:

I've had several carbs that have caused headaches in the past (and fairly recently) and when all looks like it should work, with the f.valve  shutting off the fuel, but doesn't - this has worked :

Any slight residue on the sides of the valve seat will cause the float needle to snag slightly - the needle valve should be able to move freely, modern fuels are sods for leaving residue. Use a light polish to remove the crud, you know when you've done the job - the run up to the valve seat will be the nice brass colour again. Make sure the float needle is clean too - once done the needle should move freely up and down the valve seat assembly. I normally use a cotton bud to apply the polish (brasso works well), or cotton wrapped on the end of a cocktail stick, you can spin these with your fingers, or use a drill (which is what I use, just be gentle with it).

When the carbs are at an angle, the floats don't exert as much force on the float needle (lop sided force acts on the pivot), so if the needle slightly resists movement, the needle won't shut the fuel off properly.

It's always hard to visualise issues on the net, but doing this has prevented me from doing nasty stuff to the carbs for wasting hours of my time …...

I always have fuel filters, but i suppose that doesnt stop all residue?!? That said OEM needle valves, inline filters and fuel stabiliser in winter and i just dont get any problems

Edited July 25, 2018 by wsn03

[Romaz750R]

 

Ok, I get it. I thought I should polish the needle... Probably if the left carburetor is the lowest, then the pressure on it is greater. And at an angle it warps. I understand you, I'll try, thank you all!!!

[wsn03]

4 hours ago, Romaz750R said:

 

Ok, I get it. I thought I should polish the needle... Probably if the left carburetor is the lowest, then the pressure on it is greater. And at an angle it warps. I understand you, I'll try, thank you all!!!

If you're taking the carbs off can you try loading them with fuel from a remote tank. The GPZ carbs i rebuilt took some 25 minutes to piss fuel out but they did until I made the owner buy OEM needle float valves

 

Be worth it for piece of mind. Please post back.how you get on

Edited July 27, 2018 by wsn03

[Romaz750R]

On 7/27/2018 at 6:45 PM, wsn03 said:

Be worth it for piece of mind. Please post back.how you get on

Ok. I am currently doing this.

[manden]

i bought the tour max #220719 and it stopped leaking.

[Romaz750R]

In general, the result was the following ... I once again completely checked the left carburettor. There is no leakage through the seals or the needle valve. It's all in the accelerator pump system, which is in the carburettors No. 1 and 3. In the left (No. 1) carburetor, a spring has broken, which supports the iron ball that overlapped the channel with gasoline. Therefore, gasoline from the carburettor № 2 without stop gets into the float chamber of carburetor № 1, whence it is discharged. If the channel between the carburetors is blocked, the leaks cease at any angle. 
The only thing is that it hardly can be repaired, as the bottom of the float chamber can not be disassembled.

Now it is necessary to warm up the motor, keeping the motorcycle straight, to close the gasoline cock during the parking.

 

[Romaz750R]

 

By the way, it was easy to fix by squeezing an iron ball with a grinded nail. The spring has been replaced and the iron ball is pressed back. 

No more leaks!

[duncan]

Interesting repair, I've always had the same leak and assumed floats as well, but couldn't be arsed to fix since they've been replaced fairly recent. Shut off fuel half a mile before arriving is my solution, forgetting it as often as not, and living with the ugly fuel deposits on the fairing and engine. Call it part of the oldskool "charm" 

You mean you removed the lower of the two balls? Don't see another way to get to that spring?

[Romaz750R]

Yes, it was easy enought.  I used clamp and nail (you should cut off the sharp edge, becouse nail should push on the centre of upper ball).  And i put the nut between clamp and lower ball (еру lower ball will go inside the nut). Press out slowly so as not to damage the float chamber. it will be also good to drop a little oil on the lower ball.

Replace the spring, and press the ball back (dont forget the order: upper ball - spring  -lower ball). The ball is tight enought and there is no leaks.

Oldschool "charm" is good, but better when oil and petrol inside))

[GadgetBoy]

On 7/29/2019 at 11:58 AM, Romaz750R said:

Yes, it was easy enought.  I used clamp and nail (you should cut off the sharp edge, becouse nail should push on the centre of upper ball).  And i put the nut between clamp and lower ball (еру lower ball will go inside the nut). Press out slowly so as not to damage the float chamber. it will be also good to drop a little oil on the lower ball.

Replace the spring, and press the ball back (dont forget the order: upper ball - spring  -lower ball). The ball is tight enought and there is no leaks.

Oldschool "charm" is good, but better when oil and petrol inside))

Were you able to buy a genuine replacement spring? or did you have to find something similar?

thanks!

[Romaz750R]

6 hours ago, GadgetBoy said:

Were you able to buy a genuine replacement spring? or did you have to find something similar?

thanks!

I bought a similar one. There is no in catalog. It was looked like spring of plunger (accelerator pump), but a little shorter.

[GadgetBoy]

so a spring out of a Biro pen should do it 

[Romaz750R]

20 hours ago, GadgetBoy said:

so a spring out of a Biro pen should do it 

I think thats fine!) I have a "spring shop" near

[yyt]

I'll try to help as I been there..

Check out the way I fixed the problem of the spring, I don't think you'll  find this spring at a local spring shop. the spring is very delicate brass spring.

You can first check the fuel valve (ball & spring) for proper  operation first, by filling the bottom bowel with fuel and pressing on the plunger. Fuel should squirt out of the nozzle outlet while depressing the plunger fills the plunger volume through the bottom valve, the fuel level at the bottom bowl should decrease.

I really think the the accelerator  pump is not the cause of the fuel leakage, all the accelerator system (intake valve, plunger and nozzle valve) are all under the fuel level and can't cause leaks in my opinion.

[Meatbomb99]

Hey Romaz750R I have exactly the same problem, worked it out last night and was amazed to find your post! Very happy I did.

Do you press out the top ball, that then pushed out the bottom ball through the base of the float bowl?

Edited February 18, 2020 by Meatbomb99
name correction

[Romaz750R]

10 hours ago, Meatbomb99 said:

Do you press out the top ball, that then pushed out the bottom ball through the base of the float bowl?

Yes, exactly! As i said, get nail, cut it straight, and push (as i showed on the picture) slowly not to break float bowl!.

Still all right, no leaks!

[Meatbomb99]

12 hours ago, Romaz750R said:

Yes, exactly! As i said, get nail, cut it straight, and push (as i showed on the picture) slowly not to break float bowl!.

Still all right, no leaks!

Brilliant thanks! I'll give it a go. This should be in the Top Tips section

[Ulf]

Hi,

Picking this up again. My GSXR750 - 85 with Mikuni VM29SS has the same issue , left carburator leaks from the drain.

How "strong" should the spring & ball be ? If I remove the float bowl/chamber from carburators , put them on the bench and fill both number one and three with fuel they will both be empty-ish when I check them 12 hours later.  It's a "slow" leakage , should it be no leakage at all i.e fuel level should stay the same ? 

Thank you for very good information !

 

[Romaz750R]

On 12/5/2023 at 11:06 AM, Ulf said:

Hi,

Picking this up again. My GSXR750 - 85 with Mikuni VM29SS has the same issue , left carburator leaks from the drain.

How "strong" should the spring & ball be ? If I remove the float bowl/chamber from carburators , put them on the bench and fill both number one and three with fuel they will both be empty-ish when I check them 12 hours later.  It's a "slow" leakage , should it be no leakage at all i.e fuel level should stay the same ? 

Thank you for very good information !

 

HI!

Sorry for answering late...

Marry Chistmas and Happy New Year!

Dont khow the strenge of spring, just use for measuring peaces of broken spring, and pick something same.

Still have "very very slow" leakage, but im OK with that