RD400 carb vent tubes with RD350 Y-boot

ElFuegoBlanco · January 02, 2021, 11:53:03 PM

This may be a dumb question, but I can't find the answer anywhere.

I installed an RD350 Y-boot in lieu of an airbox on my RD400. What do I do with the air vent tubes coming off the carbs? Just send them to atmosphere? Leave the tubes off?

Thanks,
Rob

Arrow · January 03, 2021, 05:04:26 AM

Hi Rob, they are not 'air vent tubes' as such. These tubes supply the air to the emulsion tubes to atomize the fuel coming through the main jet.

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1976RD400C · January 03, 2021, 06:03:35 AM

I would just install short hoses on them and bend the hose over to face down.

ElFuegoBlanco · January 03, 2021, 08:18:00 AM

Quote from: Arrow on January 03, 2021, 05:04:26 AM
Hi Rob, they are not 'air vent tubes' as such. These tubes supply the air to the emulsion tubes to atomize the fuel coming through the main jet.

Sent from my SM-G973F using Tapatalk

Oh, that makes sense. I'll run some tubes either off to the side along with the overflow tubes or up along the air filter to keep them clean. Do people install mini filters on them, then?

Quote from: 1976RD400C on January 03, 2021, 06:03:35 AM
I would just install short hoses on them and bend the hose over to face down.

Thanks for the advice. This helps a lot.

Rob

Arrow · January 03, 2021, 08:21:44 AM

Although the tubes went to the original airbox they are actually positioned where they receive unfiltered air. Not the best idea, but it worked ok for years.

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m in sc · January 03, 2021, 09:16:44 AM

you -could- route them to the bottom of the k&n filter, drill 2 small holes and insert fittings and route them. its supposed to equalize pressure to the air jet from the intake.

however

If it were my bike, id drill the brass ball out of the bellmouth on the carb and have it open and skip the air line fittings. makes it wayyy easier to clean the carb properly.

ElFuegoBlanco · January 03, 2021, 11:23:55 AM

Quote from: m in sc on January 03, 2021, 09:16:44 AM
If it were my bike, id drill the brass ball out of the bellmouth on the carb and have it open and skip the air line fittings. makes it wayyy easier to clean the carb properly.

Good news there, one of the carbs I bought from you with the ball already removed.
So should I cap the tubes then?

m in sc · January 03, 2021, 02:11:20 PM

thats right... remove the other ball and clean the airjet. then the lines don't matter. you can cap them if you want.

ElFuegoBlanco · January 03, 2021, 05:19:56 PM

Excellent. The other ball has already been removed. I'll go ahead and cap them.

Thanks for the advice.
Rob

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RD400 carb vent tubes with RD350 Y-boot