Right carb crossover issue

[Mervmaster]

I’m having a problem with a carb.

1973 xs2 650 All original. New needle and seat, floats set to 27 mm. Carbs ultrasonic cleaned and gone through.

The right side carb leaks from the overflow. It doesn’t leak when it’s the only carb connected and fed fuel.

It only leaks when both carbs are in place and fuel is running to both. Once it starts leaking it won’t stop if either petcock is on. Shutting both off stops the leak, but it resumes if you turn either back on.

I thought maybe the left side was overflowing through the crossover but the left one should overflow through the overflow first if that was the case. Both overflow tubes are clear.

It’s obviously a needle/float problem but it only happens when they’re connected. I haven’t had one of these bikes before and am unfamiliar with carbs linked this way.


Thanks for any help.

-Merv.

 

[5twins]

Is your new needle and seat aftermarket or genuine? If it's aftermarket then that explains it - it's bad. Many aftermarket ones are bad right out of the box, so much so that my dealer quit using them. Too many bikes came back leaking and he had to fix them on his dime, lol. He'll only use original replacements or genuine Mikuni ones now.

 

[Wingedwheel]

When you say linked, do you mean linked by gas line or linked carbs?

 

[Mervmaster]

When you say linked, do you mean linked by gas line or linked carbs?

Is your new needle and seat aftermarket or genuine? If it's aftermarket then that explains it - it's bad. Many aftermarket ones are bad right out of the box, so much so that my dealer quit using them. Too many bikes came back leaking and he had to fix them on his dime, lol. He'll only use original replacements or genuine Mikuni ones now.

Aftermarket, but Japanese NOS from the 70s. It’s not mikuni but it’s not an Amazon kit.


Carbs linked by fuel line.

 

[gggGary]

Yeah we've been trying to find replacement rubber tipped float valves, but no luck so far, they all work for a bit then turn into gushers.

 

[Mervmaster]

Yeah we've been trying to find replacement rubber tipped float valves, but no luck so far, they all work for a bit then turn into gushers.

So what do you do? Aftermarket carbs seems like an overreaction but if the parts aren’t available that might be the only way?

 

[Its been a long time]

So what do you do? Aftermarket carbs seems like an overreaction but if the parts aren’t available that might be the only way?

Mikuni needle valve and seat are available as far as I'm aware. The float can be tested in warm water. Submerge the float in moderately warm water. If any bubbles emerge, the float is damaged and leaking.

 

[Wingedwheel]

https://nicheindustries.com/?gad_so...MIr_6c5Y-LhwMVoojCCB2AsAd6EAAYASAAEgL43_D_BwE
Try this link

 

[Mervmaster]

Leaky float takes the cake. Didn't leak during my ultrasonic cleaning, didn't leak afterwards when dunking in warm water.

But it sure leaked when it was in the carb.

Soldered it up and it still floats nice and level.

Thanks everybody.