Topic: Accelerator pump function

[cuz]

As posted by another member, I have been trying to test my accel. pump while putting my carbs back together on my cb750k7.  His suggestion was to install the pump and then before installing the float bowl, fill it with gas then press on the pump rod to actuate it.  When i press on the pump rod some fuel comes out of the orifice that feeds the accelerator pump circuit but it is a very small amount of fuel.  How much fuel is supposed to come out of there?  I think it would take allot of time to prime the accel. pump circuit with the amount of fuel that is coming out when i test the pump.  I can not see daylight through that orifice at all.  There is a small brass (plastic?) square at the top of the hole.  Could there be a blockage behind it?  Very little carb cleaner comes through that orifice as well when I shoot it up there. 

[harisuluv]

"fuel comes out the orifice that feeds the accelerator pump"

This sounds like it pulls some fuel in, then ejects the fuel out.  In other words, it doesn't appear that any of the accel pump circuits are functioning as they should be.  The outgoing fuel that goes to the four nozzles is at the top of the float bowl in the bowl gasket area (the #2 bowl gets an oring and check valve for the accel pump circuit).

You have two check valves that you need to clear, they allow fuel to pass one way, and not the other.  If that is not what is happening, then it is not functioning correctly.

If your check valves are not working correctly, then chances are your nozzles for each carb are probably clogged too.

You have a fair bit of work to do, take your time and get it right, or it won't work.

[cuz]

This is a quote from Flybox1 "you can fill your #2 carb bowl(and accel pump installed) with liquid, and actuate the diaphragm plunger. If the system is working, you'll get a nice spray out of the check valve."

I'm wondering if I have a bad check valve.  I get more of a gurgle of fuel out the top of the float bowl where the check valve is when I actuate the diaphragm plunger.  How are these valves cleaned?

[cuz]

Further to that, if I spray carb cleaner in the hole in the bottom of the pump bowl I get a nice squirt of cleaner out of the check valve in the bottom of the pump bowl.  It seems like that one is nice and clear. 

[Phinn]

The pump's check valve gets cruddy from sitting in old gas. The valve operates with a ball bearing. I managed to take mine from totally non-functioning, after 20+ years of sitting, to normal operation by soaking it in solvents. Chemtool B12 and some others. It took days.

I think it should squirt gas up a couple of inches when you vigorously press the rod with your thumb. Yes, it squirts up from around the edges of the brass square. The rod travels about a quarter inch or so. It should also spray up when you squirt carb cleaner into the intake hole that's in the bowl.

Don't lose the o-ring.

[cuz]

Has anyone else had to clean a stuck check valve in the accelerator pump circuit?  I'm not familiar with Chemtool B12 and would like some alternatives to try and un-stick it.  I was thinking of soaking the bowl in some seafoam or even a empty a can of carb cleaner in a container and soak it in there. 

[Phinn]

Chemtool B12 is carb cleaner. Seafoam is good too. Soaking is how I freed mine up.

[flybox1]

Ultrasonic cleaner with simple green is the best bet. 
Dont try and remove the brass plugs, you'll only damage them and need to replace the whole bowl.
Test each of these in order, before installation.
To test the function of the accel pump cap (Small bowl): spray carb cleaner into the tiny hole in the lip which feeds the check valve.  Spray should shoot out the center.  wear eye protection
To test the check valve on the larger bowl, spray carb cleaner into the hole (on the face where the small bowl installs) that feeds this check valve.
To test the whole system...you can fill your #2 carb bowl (and accel pump installed) with liquid, and actuate the diaphragm plunger. If the system is working, you'll get a nice spray out of the check valve.

Be sure the diaphragm ears are nice and open, AND, your spring is installed between the diaphragm and small bowl.
(It does not go on top of the diaphragm rod )

[Phinn]

My accel pump had all three problems -- clogged check valve, closed diaphragm ears, and the spring in the wrong place. No wonder it didn't work!

I tried Simple Green too. Maybe that's what worked. Maybe it was the carb cleaner. Maybe a combination of both. But it worked for the first time immediately after a long soaking in carb cleaner, so that's what I credit with the success. Simple Green was chemically reactive with the metal, which is probably harmless, but it made me nervous.

[Ericcb750]

I just fixed this same issue where I had the check valve at the bottom of the #2 bowl blocked. I ran it through my Harbor freight ultra-sonic (per fly box's recommendations) with hot water and simple green a few times.... now spraying like a fire hose.... worked great. Also, if any of your pump nozzles (in the carb throat) are not spraying and you need to clear the little hole , try using a safety pin bent over with a pair of needle nose pliers, that way you can look from the opposite end and it's sharpe enough to clear any blockages.

A bit of spray carb cleaner should shoot right out in a nice stream through both check valves (wear glasses, carb cleaner in the eye is no fun) and you'll be able to tell when it's functioning properly... Flybox has been a huge help on me re-building (Correctly) my PD style carbs.

Good luck, let me know if you have any questions. I may be able to help

[cuz]

I soaked the carb body (half of it was submersed) in some simple green last night.  I have the pressure washer version of simple green.  As Phinn stated, the carb body did react with the simple green and it changed color a bit.  As I don't have an ultrasonic cleaner I think I will soak it in some carb cleaner for a couple days to see if that frees it up.  The check valve in the accel. pump bowl is good to go and when I spray cleaner in through the pump circuit I get a nice spray out of each of the nozzles in the carb body.  Almost there, just need to free up the one check valve. 

[Ericcb750]

Oh my bad, I forgot to tell you, I use the HD PRO Simple Green (which is actually purple , ironic) but it's safe for aluminum... you can get big jugs at Home Depot. yeah the one that's part of the actual float bowl on mine wasn't a problem at all.... it was that darn one in the little cap at the bottom that houses the actual pump. keep working on it with the soak and carb spray. Good Luck buddy.

another tip ( i learned the hard way) make sure they're all spraying a nice even stream BEFORE putting it all together and mounting up on the bike.... will save you from having to take them off again. Just make sure you go over everything related to the function of the carbs and double check before you re-assemble and mount up...

Let me know if I can help at all. This forum is where it's at! Everyone here is awesome and I attribute my first SOHC Build to everyone here's help.

[harisuluv]

I soaked the carb body (half of it was submersed) in some simple green last night.  I have the pressure washer version of simple green.  As Phinn stated, the carb body did react with the simple green and it changed color a bit.  As I don't have an ultrasonic cleaner I think I will soak it in some carb cleaner for a couple days to see if that frees it up.  The check valve in the accel. pump bowl is good to go and when I spray cleaner in through the pump circuit I get a nice spray out of each of the nozzles in the carb body.  Almost there, just need to free up the one check valve. 

Just freeing up the check valve isn't all there is to it.  Fuel should only pass ONE direction, so if you haven't verified that is the case, the system isn't going to work.

[mystic_1]

Indeed, these valves can become stuck in the "open" position.

This can be checked by applying vacuum to the same feed port that you're spraying fluid into now, you should be able to draw a vacuum and hold it, otherwise the valve still has crap in it.

mystic_1