Topic: 77-78 PD Accelerator Pump Check Valve Removal

[DHuffman]

Hello all,
I'm in the process of rebuilding the carbs on my '77 CB750F2.  I have the PD42B carbs, which have the accelerator pump.  This system has two check valves to restrict flow direction, which consist of a spring loaded steel ball and a (in my case) plastic square plug.  The valve on the float bowl can be removed by pushing it out through the channel (I used a carb cleaner straw).  However, I have been unable to get flow through the valve on the accelerator pump cover on the bottom of the float bowl, and because of the port configuration, I am unable to push it out as I did with the other.

I stumbled upon this useful tutorial PDF on a way to remove it and thought I'd share it in case anyone else is having this problem:

[flybox1]

Ultrasonic cleaner w simple green will work.  Dont drill the plug. 

[DHuffman]

Okay. Just wanted to make sure that it wouldn't each the plastic plug.

Thanks again flybox.

[DHuffman]

After soaking it in simple green for a day and still having no luck. I made the stupid decision to try to push the square plug down thinking it may free it up to get it out. This just made the situation worse, as it compressed the spring for the check valve, leaving no hope of getting flow through the passage.

However, I was able to pry the plug up little by little with a small needle. I then smacked the cover face down on my workbench repeatedly. This must have freed up the steel ball, because I now get good flow through the valve. 

My concern now  is that it does not seem to seal 100% in the opposite direction. My air compressor blow nozzle fits perfectly over the check valve. I applied ~60 psi of air pressure to the valve opposite to flow direction, and get a very small amount of air flow though it.

Is that a major concern?

[flybox1]

Why 60psi?  gas sitting in the bowl doesnt provide that much pressure 

As long as you can get carb cleaner to spray thru the check valve in reverse, you're good.
If the accel pump diaphragm is not moving, the fuel in the accel pump circuit is not moving.  its fine.

[DHuffman]

No rhyme or reason to the 60 psi. I just turned the valve on my compressor and that's where it went to. I wanted to see if the valve would seal under pressure, and had no idea how much it is subject to in reality. 

Ordered carb kits today, so should be reassembling the carbs next week.