Hey I just put together a yz 250 out of two bikes but one of the motors have an extra nipple coming out. It's the one between the piston and the reeds. The cylinder says ftz racing on the side. Any ideas? It runs good with no cap on the nipple. 
Extra vent between the reeds and piston on yz 250??
- Thread starter gladeslife
- Start date
from the casting number on side it should be a 2001 cylinder and i've seen a couple oem schematics for the 01 that does not show that nipple.of course the schematics are crappy quality as all oem ones are, but not familiar with ftz racing products other than name. but i would just plug it off if it were me.
Nitrous inlet. 
@SRAD97750 Will know more... I think his 500 is like that.
I have never seen that before and it is definitely not stock for a single cylinder 2 stroke.
I would cap it.
On my sportbikes though, every cylinder has one of those.
They are for balancing multiple carbs or, YES... NITROUS PORTS.
With NOS there are two ports at the top of the intake, one for fuel, the other for Nitrous. -BIG DAN
I would cap it.
On my sportbikes though, every cylinder has one of those.
They are for balancing multiple carbs or, YES... NITROUS PORTS.
With NOS there are two ports at the top of the intake, one for fuel, the other for Nitrous. -BIG DAN
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Cap it or add a nitrous bottle. I have never ran across that either. Maybe it helps it idle "ALL DAY LONG"
I contacted ftz racing and they said it's for a fuel pump that works off a pulse. I would think it would run like crap if it's open but it doesn't.
Is the orifice smaller than the inlet? Might not be drawing as much vacuum e as you think.
in olden days some 2st had a surge bottle on the side of the motor. It would charge with fuel when off throttle and at high rpms. Then when you opened the throttle it would suck in the extra fuel/air mix for an initial go fast charge of fuel. Didnt last but a few years. Maybe this is what it is for.
Come to think of it, I do have this device on my WR500. Yamaha ENERGY INDUCTION.
It has a 3/4" nipple coming out of the top of my intake. Large Hose to a plastic reservoir.
https://www.dirtbikeaddicts.com/content/attachments/017-jpg.11286/
https://www.dirtbikeaddicts.com/content/attachments/008-jpg.16775/
Very interesting...
-BIG DAN
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lots of them had the so called boost bottles. that one has the line cumming in on the downwind side of the reeds though, and as stated would work fine to run a fuel pump. that one will get a pressure pulse that squeezes the diaghram of the pump.
Imagine how it would run if the nipple is plugged, the float set, and the carburetor jetted properly. If it is running good with a giant intake leak like that should be giving, you are going to love it when it is right.
Imagine how it would run if the nipple is plugged, the float set, and the carburetor jetted properly. If it is running good with a giant intake leak like that should be giving, you are going to love it when it is right.
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Dan, plug it, jet it, rip it, report it
I'll report back. I plugged it but haven't taken It for a ride BC I'm waiting for wheel bearings
