crankcase breather

bultaco4ever · Post by **bultaco4ever** » 02:33 pm May 31 2016

My 93 doesn't have the breather tube that goes on the fitting on the back of the center case. (Backside of kick start mechanism) Where does the breather hose go? What home remedy is just as effective a factory part?

eprovenzano · Post by **eprovenzano** » 02:39 pm May 31 2016

It's just a small hose that's normally run down to the the front of the swing arm... Nothing fancy, just a peice of hose will work... Just make sure to cut the end on a 45 degree angle... this helps to keep the hose from getting clogged.

greener200h · Post by **greener200h** » 04:34 pm May 31 2016

almost the same. I route my hose up near the top of the air box, under the seat. I cut a small piece of old air filter material and stuff it in end of hose to keep dirt & maybe water out.

Tedh98 · Post by **Tedh98** » 05:05 pm May 31 2016

+1 on running it up to the airbox.

Of the 4-5 KDXs I have bought over the years, they have all had the hose going into the airbox.

Post by **KDXGarage** » 07:39 pm May 31 2016

It goes to the airbox. A normal tube will do.

Friedom · Post by **Friedom** » 09:41 am Jun 08 2016

Furthermore, if you run it to the swing arm you'll suck water in if you do a deep crossing. Ask how I know..

Sent from my SM-G930V using Tapatalk

G22inSC · Post by **G22inSC** » 10:43 am Jun 08 2016

Friedom wrote:Furthermore, if you run it to the swing arm you'll suck water in if you do a deep crossing.

I have the line routed up to my airbox as well on all my bikes, but I'm curious...why do we do this for the trans vent line only? The carb vent lines still hang below the cases.

Friedom · Post by **Friedom** » 10:54 am Jun 08 2016

Carb vents are overflow lines. As far as I know, if the carb is working right it would never suck in water (at least not the full length of those lines).
You would think there's not a suction in the tranny either, but when the engine hits water, things cool and contract, so the internal pressure decreases and that vent line is the easiest way for air (or water) to flow in and equalizer that pressure.
The carb doesn't get hot like the engine, and has smaller internal volume and gas keeping it cool.
We have this issue on rear axles on 5th gen 4runners. The breather hose has a 1 way valve on it so when things get hot the extra pressure is let off. In theory, it won't suck any fluids in because of the one way valve, but instead when you hit water it'll create such a vacuum from thermal contraction that it sucks water in through the seals. No Bueno, as there's no sight glass to see that your drive train is operating in mud.
That reminds me, I need to mod my breather hose soon...

Sent from my SM-G930V using Tapatalk

MotoArts · Post by **MotoArts** » 10:25 pm Jun 27 2016

I always use a small fuel filter on trans and (automotive rear end) lines.
Surely can't hurt, no matter where you route the line. If you use the clear ones, you can tell if funk has compromised anything.
They're cheap, too ;)

Post by **KDXGarage** » 12:38 am Jun 28 2016

Here is more mumbo jumbo on this topic. As best I remember, in new condition, KDX's from 1986 on (maybe earlier??) had it ran from the transmission into the airbox. If you bought yours and it was used, then all bets are off.

PC Racing used to offer a carb vent hose T kit that would allow an old school trick to be done with a retail package. Back in the day, several people would buy a plastic T and more carb vent hose to run one end down to the swingarm and one to the air box up high, away from the water.

OK, THIS!! I found it.

http://www.pcracingusa.com/Carb-Vent_p_84.html

KDXRIDER.NET

KDXRIDER.NET