Not having a check valve on the breather wouldn't cause seal wear. In the stock configuration, there was no valve, just a hose.
 
No, you don't absolutely need one, but many of us feel they are beneficial. Normally, with an open hose, pressure come out when the pistons force air down into the crankcase during their down stroke, but then some air gets sucked back in when the pistons go back up. With the one way check valve, air is only allowed to come out, not back in. This can create a slight vacuum in the crankcase and that's said to be beneficial for preventing oil leaks. It's also said that the engine can produce a bit more power like this but I can't say I've noticed that. The valves many of us use are available at many auto parts stores and don't cost much, only about $5 .....

NM4t1Dh.jpg


The large intake side is a perfect fit in the breather hose, and the 90° configuration works perfectly to direct the outlet down onto the pod. I started out using a small K&N filter on the end of my hoses. It was always wet with oil. I never saw it actually drip any but it was very wet. These check valve seem to work much better. Like I said, I've never seen any oil coming out of them.
 
Fuel lines don't have "vacuum leaks"
:popcorn:

I wasn't sure if the po had vacuum petcocks or gravity .
If they are vacuum then its the engine vacuum that operates the petcock diaphragm so I'd expect you might get suction at a loose connection ;)

https://www.motorcyclepowersportsnews.com/gravity-and-vacuum-fuel-delivery-systems/
Gravity and Vacuum Fuel Delivery Systems
Some vehicles have vacuum operated petcocks. The fuel valve is held closed by a spring when no vacuum is present. The fuel valve is opened when the engine applies vacuum to the fuel valve diaphragm.
 
Last edited:
No, you don't absolutely need one, but many of us feel they are beneficial. Normally, with an open hose, pressure come out when the pistons force air down into the crankcase during their down stroke, but then some air gets sucked back in when the pistons go back up. With the one way check valve, air is only allowed to come out, not back in. This can create a slight vacuum in the crankcase and that's said to be beneficial for preventing oil leaks. It's also said that the engine can produce a bit more power like this but I can't say I've noticed that. The valves many of us use are available at many auto parts stores and don't cost much, only about $5 .....

NM4t1Dh.jpg


The large intake side is a perfect fit in the breather hose, and the 90° configuration works perfectly to direct the outlet down onto the pod. I started out using a small K&N filter on the end of my hoses. It was always wet with oil. I never saw it actually drip any but it was very wet. These check valve seem to work much better. Like I said, I've never seen any oil coming out of them.

You're the man. Thanks
 
I can't believe I'm saying this. Fuel lines are lightly PRESSURIZED. NOT vacuum. The quantity of the fuel in the tank will determine the amount of pressure in the line.

so vacuum petcocks work by gravity ........not vacuum........ is that what you are saying ?:rolleyes:

Strictly speaking Its not the quantity of fuel in a tank that determines pressure its the 'head' of fuel above the carburettor
 
No, you don't absolutely need one, but many of us feel they are beneficial. Normally, with an open hose, pressure come out when the pistons force air down into the crankcase during their down stroke, but then some air gets sucked back in when the pistons go back up. With the one way check valve, air is only allowed to come out, not back in. This can create a slight vacuum in the crankcase and that's said to be beneficial for preventing oil leaks. It's also said that the engine can produce a bit more power like this but I can't say I've noticed that. The valves many of us use are available at many auto parts stores and don't cost much, only about $5 .....

NM4t1Dh.jpg


The large intake side is a perfect fit in the breather hose, and the 90° configuration works perfectly to direct the outlet down onto the pod. I started out using a small K&N filter on the end of my hoses. It was always wet with oil. I never saw it actually drip any but it was very wet. These check valve seem to work much better. Like I said, I've never seen any oil coming out of them.

Hey so I bought a check valve at the parts store, but I'm a little confused about one thing. If the crankcase nipple that you attache the breather and valve to is just open wouldn't oil just run down the side of my engine? Or does the valve allow pressure to be released? (Also found the stock hose for my bike).
E793898F-99F4-4DF3-8230-EF31532BD260.jpeg
B8B7D177-0335-48A5-B659-5B5B0D256A48.jpeg
 
Ok, so I installed the crankcase vent and check valve and replaced the fuel lines with thinner transparent ones. Nothing seems to have change. Still have a crazy air leak. However, the leak is not coming from my fuel line and filters its probably my manifold on the right carb boot. Sorry for the confusion. My right cylinder is still getting lots of fuel. Is it normal for the fuel level to go past the float bowls on the side that my petcock is turned off? Right plug is still soaked with fuel.
BE03461C-A7EB-4ED6-B338-338DD55914B9.jpeg
71A0FF20-58EC-4F18-922B-2B30325FEA2A.jpeg
 
IMO The right float valve is not working, get that fixed first. Fuel level in the line connected to the turned off petcock is meaningless. If the carbs are both working as they should the second petcock will be just fine on OR off. Make a float bowl fuel level checker connected to the float bowl drain, all will be revealed.
 
However, the leak is not coming from my fuel line and filters its probably my manifold on the right carb boot. Sorry for the confusion.
However, the leak is not coming from my fuel line and filters its probably my manifold on the right carb boot. Sorry for the confusion.
Now you are getting there !
Upon reinstallation of the carbs into the manifolds I would discourage use of an oil lubricant. I would encourage to clean the manifolds. Even just a dab of soapy water can help the carbs fit into the manifolds properly .
Due to the lack now of the air box rear carbs support. It is more important for good and solid carb installation.
... Say if a guy did use light grease on the boots and then did not adequately tighten the clamps, Then while riding in an unfamiliar town which is riddled with speed bumps, excessive speed over those bumps could easily result in the carbs just falling out of the manifolds ? And there you would be wondering WTF ? :whistle: (I cannot say who this may have happened to ?)
:oops:-RT
 
Now you are getting there !
Upon reinstallation of the carbs into the manifolds I would discourage use of an oil lubricant. I would encourage to clean the manifolds. Even just a dab of soapy water can help the carbs fit into the manifolds properly .
Due to the lack now of the air box rear carbs support. It is more important for good and solid carb installation.
... Say if a guy did use light grease on the boots and then did not adequately tighten the clamps, Then while riding in an unfamiliar town which is riddled with speed bumps, excessive speed over those bumps could easily result in the carbs just falling out of the manifolds ? And there you would be wondering WTF ? :whistle: (I cannot say who this may have happened to ?)
:oops:-RT

Ahaha duly noted. I'll check float leaks, float valve and fuel level in the bowl today when I get home.
 
Now you are getting there !
Upon reinstallation of the carbs into the manifolds I would discourage use of an oil lubricant. I would encourage to clean the manifolds. Even just a dab of soapy water can help the carbs fit into the manifolds properly .
Due to the lack now of the air box rear carbs support. It is more important for good and solid carb installation.
... Say if a guy did use light grease on the boots and then did not adequately tighten the clamps, Then while riding in an unfamiliar town which is riddled with speed bumps, excessive speed over those bumps could easily result in the carbs just falling out of the manifolds ? And there you would be wondering WTF ? :whistle: (I cannot say who this may have happened to ?)
:oops:-RT

Ahaha duly noted
IMO The right float valve is not working, get that fixed first. Fuel level in the line connected to the turned off petcock is meaningless. If the carbs are both working as they should the second petcock will be just fine on OR off. Make a float bowl fuel level checker connected to the float bowl drain, all will be revealed.
Did the float test and it seems to be ok. The floats are new and I've tested the valve before. Seems good. Initially I thought that maybe my valve seal was leaking oil into my cylinder thats why my plug is wet? Any thoughts?
9A3BE887-FAD6-4EA1-9B22-6C448CF8DF1F.jpeg
 
Correct. But you could check or swap the plug caps and/or plug wires. Also check the plug cap to wire and wire to coil connections. Maybe something came loose.
 
Back
Top