Overflow tube issue

detours · 08-17-2016, 06:42 PM

The idea is to put a one-way check valve on the PCV line to the airbox.

As the piston moves up and down, it creates alternating positive and negative pressure in the crankcase. When the piston comes down, positive pressure helps push fuel and water vapor out of the crankcase. When it goes back up, negative pressure sucks some of that vapor back in.

This may explain the condensation we see in the OCS. On the low pressure cycle, the vapors cool off, condensing before it reaches the airbox and dripping into the catch tube.

A PCV check valve would only allow vapor to escape, hopefully preventing the low pressure and condensation. I need to find time to get to the auto parts store and look for a check valve that fits the line to the airbox.

jbfla · 08-17-2016, 09:03 PM

Quote:

Originally Posted by detours

The idea is to put a one-way check valve on the PCV line to the airbox.....

Detours, Does the PCV valve rely of suction (negative pressure) from the airbox?

When I replaced the hose today from the crankcase to the airbox, I put my finger over the end of the hose with the engine running and could feel nothing.

Replaced the plastic hose with braided vinyl hose (1/2" ID)

jb

jbfla · 08-17-2016, 09:06 PM

Detours,

Nevermind, I re-read your post and all is clear!

Quote:

Originally Posted by detours

...
As the piston moves up and down, it creates alternating positive and negative pressure in the crankcase. When the piston comes down, positive pressure helps push fuel and water vapor out of the crankcase. When it goes back up, negative pressure sucks some of that vapor back in....

jb

pyoungbl · 08-17-2016, 10:28 PM

With our 250cc single, I wonder how much pumping action we actually have. I suspect we are not looking at a large volume of air being moved up into the airbox. It's more like a fixed volume being pushed back and forth along the hose going from crankcase to airbox. Of course the vacuum at the air box will suck from the crankcase but it's not going to be a hurricane flow of air in that tube.

I'm still interested in figuring out why some Zongs have high concentrations of fuel in the crankcase, as well as why some have a bunch of liquid in the drain valve. If all had these issues it would be easier to figure this out but some do and others don't.

jbfla · 08-17-2016, 11:39 PM

Quote:

Originally Posted by pyoungbl

With our 250cc single, I wonder how much pumping action we actually have. I suspect we are not looking at a large volume of air being moved up into the airbox. It's more like a fixed volume being pushed back and forth along the hose going from crankcase to airbox. Of course the vacuum at the air box will suck from the crankcase but it's not going to be a hurricane flow of air in that tube......

P, I could not feel any suction from the airbox with the engine running (at idle).

Perhaps at higher rpm, while the bike is underway, some is developed.

On the other hand, when I removed the hose from the engine,(engine running at idle), and put my finger over the crankcase opening, the pulses were readily evident.

P, have you had any resolution of you RX3's fuel in the oil problem?

jb

pyoungbl · 08-18-2016, 10:12 AM

Quote:

Originally Posted by jbfla

P, have you had any resolution of you RX3's fuel in the oil problem?

jb

No resolution yet. Actually, it has just been too hot/humid for me to ride the bike. Remember, I did a 7500 mile ride in July so I have already had my dose of hot riding for 2016. I installed a 90C thermostat and idled the engine to get all the air bubbles out of the system. I have seen the left radiator get up to 190F (the fan never came on) sitting in the garage. When I get the bike back on the road I hope to see higher crankcase temps than the last time I checked.

BlackBike · 08-18-2016, 12:40 AM

Quote:

Originally Posted by pyoungbl

With our 250cc single, I wonder how much pumping action we actually have. I suspect we are not looking at a large volume of air being moved up into the airbox. It's more like a fixed volume being pushed back and forth along the hose going from crankcase to airbox. Of course the vacuum at the air box will suck from the crankcase but it's not going to be a hurricane flow of air in that tube.

I'm still interested in figuring out why some Zongs have high concentrations of fuel in the crankcase, as well as why some have a bunch of liquid in the drain valve. If all had these issues it would be easier to figure this out but some do and others don't.

Oh God, dare I say it, but is this where break in comes in to play with the amount of fuel getting past worn rings. Every bike is going to vary depending on the course of break in and the eventual milage piston wear. Now we circle back

just shoot me!

katflap · 08-18-2016, 01:48 PM

Quote:

Originally Posted by pyoungbl

With our 250cc single, I wonder how much pumping action we actually have. I suspect we are not looking at a large volume of air being moved up into the airbox. It's more like a fixed volume being pushed back and forth along the hose going from crankcase to airbox. Of course the vacuum at the air box will suck from the crankcase but it's not going to be a hurricane flow of air in that tube.

I'm still interested in figuring out why some Zongs have high concentrations of fuel in the crankcase, as well as why some have a bunch of liquid in the drain valve. If all had these issues it would be easier to figure this out but some do and others don't.

There is also blow by gasses to add into the flow.

I have been reading this article on it, though it is talking about car engines I was surprised at how much there is. On my rough calculations using the equation quoted in the article, there could be as much as 1.8 litres of blow by in a 1 minute at idle.

The article here
http://www.106rallye.co.uk/members/d...hersystems.pdf

So i'm going to scientifically test this

by seeing how long it takes to fill up a 10 litre *bin bag , attached to the crankcase breather.

you never know it might just work

* translation for you guys, bin bag = garbage bag

BlackBike · 08-18-2016, 03:43 PM

Quote:

Originally Posted by katflap

There is also blow by gasses to add into the flow.
I have been reading this article on it, though it is talking about car engines I was surprised at how much there is. On my rough calculations using the equation quoted in the article, there could be as much as 1.8 litres of blow by in a 1 minute at idle.
The article here
http://www.106rallye.co.uk/members/d...hersystems.pdf
So i'm going to scientifically test this

by seeing how long it takes to fill up a 10 litre *bin bag , attached to the crankcase breather.
you never know it might just work

* translation for you guys, bin bag = garbage bag

i think the engineers of this bike just intended its owners to be carving a few roads and hitting a few trails with this bike.

sounds interesting

08-17-2016, 06:42 PM	#1
detours Join Date: Sep 2014 Location: Arvada, CO Posts: 1,004	The idea is to put a one-way check valve on the PCV line to the airbox. As the piston moves up and down, it creates alternating positive and negative pressure in the crankcase. When the piston comes down, positive pressure helps push fuel and water vapor out of the crankcase. When it goes back up, negative pressure sucks some of that vapor back in. This may explain the condensation we see in the OCS. On the low pressure cycle, the vapors cool off, condensing before it reaches the airbox and dripping into the catch tube. A PCV check valve would only allow vapor to escape, hopefully preventing the low pressure and condensation. I need to find time to get to the auto parts store and look for a check valve that fits the line to the airbox. __________________ Red 5 standing by! 2015 CSC red RX3 with 19" front wheel, Shinko 804/805, skid plate, tall seat, 13T/45T sprockets, progressive shock, Winyoochanok windshield, GENSSI LED headlight, SW-Motech tankbag, Shorai Lithium battery 2014 Ural Patrol
	1

08-17-2016, 10:28 PM	#4
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	With our 250cc single, I wonder how much pumping action we actually have. I suspect we are not looking at a large volume of air being moved up into the airbox. It's more like a fixed volume being pushed back and forth along the hose going from crankcase to airbox. Of course the vacuum at the air box will suck from the crankcase but it's not going to be a hurricane flow of air in that tube. I'm still interested in figuring out why some Zongs have high concentrations of fuel in the crankcase, as well as why some have a bunch of liquid in the drain valve. If all had these issues it would be easier to figure this out but some do and others don't.
	1