Mikuni Air vent tubes & Breather pipe

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Player#3

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Hi,

I have just swopped my Amals for single Mikuni and and wondering about the two air vent tubes. They seems to just hang down under the carb. When I switch the full on the lower air vent tubes just gushes petrol.
Maybe a sticking float ? What else. Are they supposed to go somewhere ?

How about the balance pipe that was connect between the Amals. Where should the breather pipe be connected now as there is no place for it on the K&N air filter

Regards,
Sean
 
Player#3 said:
Hi,

I have just swopped my Amals for single Mikuni and and wondering about the two air vent tubes. They seems to just hang down under the carb. When I switch the full on the lower air vent tubes just gushes petrol.
Maybe a sticking float ? What else. Are they supposed to go somewhere ?

How about the balance pipe that was connect between the Amals. Where should the breather pipe be connected now as there is no place for it on the K&N air filter

Regards,
Sean
Click to expand...

Faulty needle/seat. Floats don't "stick" on them. Please do not rap on the bowl as old duffers will suggest, dismantle and repair as needed. The fact you are asking this means you need help with it, any mechanic buds? Jap bike mechanic/enthusiast friends?

The vent lines are correct, open to atmosphere, hanging down.
 
Sometimes the floats stick on Mikunis. Most of them have floats that slide up and down on thin brass rods. When a bike is left sitting over the winter the fuel sometimes gums those rods up a bit, especially if the carbs are not drained. Usually the problem solves it's self, since that gum is pretty soluble in gas. Tapping the side of the float bowl does solve that problem. Really it is just giving the float a shake. If it doesn't you may have some dirt under the float needle.

I have one bike that does this every year when I first start it up, then it is no problem till the next time I store it.
 
If you want, get some tubing that will fit, and replace the vent lines with longer ones that hang down behind the trans and out of sight.
 
tricatcent said:
Sometimes the floats stick on Mikunis. Most of them have floats that slide up and down on thin brass rods. When a bike is left sitting over the winter the fuel sometimes gums those rods up a bit, especially if the carbs are not drained. Usually the problem solves it's self, since that gum is pretty soluble in gas. Tapping the side of the float bowl does solve that problem. Really it is just giving the float a shake. If it doesn't you may have some dirt under the float needle.

I have one bike that does this every year when I first start it up, then it is no problem till the next time I store it.
Click to expand...


Hi,

You are right on with this suggestion. I took the carb off and opened it and it was flull crusty dirt and one float was completely stuck. After soaking and putting the parts in an ultra-sonic bath it all works nice and smoothly again.

How about the old rather pipe. Can it be removed of must there be a vacuum in the crank ?

Regards,
Sean
 
Player#3 said:
How about the old breather pipe. Can it be removed or must there be a vacuum in the crank ?

Regards,
Sean
Click to expand...

I routed mine to where it blows against the side of the K&N element so that the fumes that invariably emanate from said pipe will be ingested and burned by the engine. I'm running a breather check-valve, which means that "air" is only going out. If you're not, you should consider running one, or you'll be pulling unfiltered air back into the oil tank. In this case, you'd need to hard plumb the breather line to the inside of the air filter.

Nathan
 
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