carb vent on mikuni 32 shoots out fuel - HCS Snowmobile Forums

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Old 11-09-2019, 05:23 PM   #1 (permalink)
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Default carb vent on mikuni 32 shoots out fuel

On a 96 indy trail when it is sitting idling their is fuel streaming out the hole on the top of the carburetor. I have gone through the carb countless times and it is clean as a whistle. Any idea what is wrong?
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Old 11-09-2019, 05:23 PM   #2 (permalink)
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Have you pressure tested the N&S's?
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Old 11-09-2019, 05:35 PM   #3 (permalink)
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I have another new needle and seat. Will throw that in the carb. Thanks.
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Old 11-09-2019, 11:12 PM   #4 (permalink)
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Originally Posted by Boggy View Post
On a 96 indy trail when it is sitting idling their is fuel streaming out the hole on the top of the carburetor. I have gone through the carb countless times and it is clean as a whistle. Any idea what is wrong?
Change the needle and seat. You need a magnifying glass to the marks on the seat.
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Old 11-10-2019, 08:06 AM   #5 (permalink)
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My 96 Polaris Shop Manual says the Indy Trail carbs are 34 mm and there are 2 of them.

I recommend a wet pressure test when the fuel level is too high. This is done with the carb in a vise sitting upright as it is in the sled. Attach a clear fuel hose about 12-18" long. Fill it with fuel, then apply low pressure air 5-6 psi while holding the hose vertical.
You will see the fuel level drop a bit in the hose until the float bowl is full. Then it should stay at that level in the hose.

If it doesn't, there is a problem with the float system.

Don't assume it's only caused by the Needle/seat leaking. It can also be caused by float level set wrong, wrong size or height needle/seat, a float that doesn't have as much buoyancy as normal, a dragging/sticking float, etc. It can even be caused by a plugged bowl vent passage trapping air inside the float bowl as fuel is pumped in.

The next step is to drain all fuel out, invert the carb, remove the bowl and inspect everything. If the N/S is larger than 1.5 mm, it will not hold much fuel pressure.
If all looks okay, use the same fuel hose again to apply low air pressure to the fuel inlet and needle/seat while spraying WD-40, etc., around the N/S. The leak should be apparent by bubbles seen.

Good luck.
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Old 11-10-2019, 09:35 AM   #6 (permalink)
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I once had a similar issue with a 34mm carb on a indy 400. Found a sliver of crap under the seat needle not allowing it to fully close. At any rate best just to replace the n/s assembly on those older sleds.
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Old 11-13-2019, 06:15 PM   #7 (permalink)
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Changed out the needle and seat and all is well. Thank you. These are not the original carbs. Trail engine transplanted into my 78 cobra.
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Last edited by Boggy; 11-13-2019 at 06:23 PM.
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Old 11-13-2019, 07:02 PM   #8 (permalink)
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Changed out the needle and seat and all is well. Thank you. These are not the original carbs. Trail engine transplanted into my 78 cobra.
NICE! Brings back memories of my 78 TXL. Still got the motor on the shelf.
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Old 11-13-2019, 09:12 PM   #9 (permalink)
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Changed out the needle and seat and all is well. Thank you. These are not the original carbs. Trail engine transplanted into my 78 cobra.
Nice job for snowmobile resto mod
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Old 11-14-2019, 05:21 PM   #10 (permalink)
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Quote:
Originally Posted by Boggy View Post
Changed out the needle and seat and all is well. Thank you. These are not the original carbs. Trail engine transplanted into my 78 cobra.
Looks more like you transplanted some of a Cobra onto a Indy Trail
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