Hose Nipple/Check Valve; Education Needed

[boscoe99]

The VZ250FTLR calls these check valves. Other two stroke parts books call them hose nipples.

Are they all check valves, at times misstated as a hose nipple, or do some models actually use just a hose nipple with no internal valving?

Can someone describe the theory of operation insofar what it is these doohickys are actually doing?

[panasonic]

When you find out let us know....lol

Something to do with the pressure pulses on the reeds??? I don't know.

[99yam40]

On my C40 the crankcase has both, but on each hose there is a check valve. just not both ends
from what I understand the check valves and hoses from the bottom of each individual crank case section helps suck liquid residue that pools up at the bottom and moves it to where it can be recirculated to be burned

[pstephens46]

I don't know how this oiling system works on the mysterious Z motor. Pulling this out of my rear. I am bored. Is it a recovery system or does it "oil" during normal operation? Assuming oil flows during normal operation AND they are indeed one way check valves......Does this system trap oil for the next start cycle? Please tell us.....

[99yam40]

On my C40 they were called recirculating check valves I believe.

not good to let it all pool up and leave it there to keep building up.
it has to go some where eventually

[pstephens46]

Your motor is carbed through to crank? The HPDI flows fuel to top of piston. Oil has to flow to other parts. I always found these motors to be interesting. Maybe he or Rod will tell us.

[boscoe99]

I don't know how this oiling system works on the mysterious Z motor. Pulling this out of my rear. I am bored. Is it a recovery system or does it "oil" during normal operation? Assuming oil flows during normal operation AND they are indeed one way check valves......Does this system trap oil for the next start cycle? Please tell us.....

On darn near all Yam two strokes, except for the premix models and the OX66 EFI models, oil is pumped to a point just behind each of the carburetors. In the Z and VZ models (HPDI's) the oil is injected right behind the air intake throttle valves. Airflow picks it up and takes it into the engine along with the gasoline.

In the OX66 models the oil is pumped to the VST where it is mixed with gasoline. From there it is similar to a premix model, except the gasoline/oil mix is injected into the intake system instead of being drawn into the intake system via a carburetor.

I tend to agree with 99yam about the recirculation system being designed to capture surplus oil at one point and deliver it to another point where it can be better utilized. Ultimately being burned with the gasoline.

Hoping that rodnut or someone can confirm this. Also, I suspect rodnut might be the only one that can tell me if the parts are check valves in all models or simple hose nipples in some and check valves in others.

[99yam40]

in that parts blow up I see them listed as #3,#5, and #8
what are they listed as/ labeled?

I know on my little C40 some are listed as nipples and others listed as check valves

Looks like 3 are listed as just nipples
5 and 8 are listed as check valves

[zenoahphobic]

I wonder if it just another language thing. Check might be loosely used to equalise or direct air/fuel/oil, stopping these going elsewhere ; or mean the holding of the hoses to the body., placed at the ends of the hoses to keep them in check.

I doubt that there are any valves in them. They look like they are designed to make the hoses attach flat (at right angles)..

I've always thought the use of the adjective " check" as a noun "valve" a bit hard to grasp. But I suppose I can remember a condom being call a wet check.

[99yam40]

the manuals give ways to test check valves.
there are differences between check valves and just nipples for hoses

[rodbolt17]

and that is the recirc system in a nutshell. not all motors used it. the screens on the old jonny/rudes would clog. the screens on the old chryslers clogged,the inline mercs never used them.
some V model and most inline yamahas used a recirc system to move puddled oil or a mix to another cyl for burning.