Topic: Accelerator pump?!?!

[SurfinBird]

'78 CB750F

Got my carbs clean, adjusted the valve clearance, got the tank back on, put the carbs back on time to give it a go and see if this thing starts. I figure I should check to make sure the pump is squirting fuel since I didn't have the airbox on it. Twist the throttle...nothing, no fuel coming out the posts. Checked the bowls, all have fuel, a little overflow, no big deal, adjust the floats.

What do I need to look for on the pump? While I had the carbs apart I saw the mickey mouse ears were plugged. I ran a small nail through them both, one cleared nicely, the other felt like in never had a hole, the hole looks a lot smaller than the other and ragged, not clean like the other one. I went through the forums and kept reading about check valve in the base of the pump, I read the article about cleaning them so i'll give that a go and I ordered an new diaphragm and spring.

Should I look at anything else? Is that enough to keep this thing from starting up? It's never started and I was too discouraged, from not seeing fuel come out of the pump, that I didn't even bother putting the battery back in.

[bollingball]

First off this could be done before you put the carbs on the bike. Both ears need to be open. Mount carb rack on a jig get them level fill with gas work the pump by hand if carbs are dry this will take 10 to 15 pumps to fill the cross over pipes and then all four should squirt. On the bench you don't need to put the bowl gaskets on(if fuel level is below bowl gasket) but you do need the pump oring or it will leak when pumping by hand.

This is a simple jig for testing float level and pump don't laugh it is all I had laying around.

                         Ken

             

[Trav-i]

Surfinbird, I had the same problem earlier this year.  Here is a link to my old thread it had a lot of good tips in it, along with a link to a good article on how to clean the check valves in the system.  My problem was the check valve in the pump bowl was stuck, I cleaned it and it's worked perfectly ever since.

http://forums.sohc4.net/index.php?topic=82091.0

Hope some of this helps ya out.

Good Luck

Travis

[bollingball]

The pump would not keep it from starting. In one pic you can see I use the clear tube method for fuel level 2mm to 3mm below bowl gasket as I said everything is done on the bench so you don't have any surprises once on the bike I hate taking them off and on 

                          Ken

[SurfinBird]

Thanks guys. I'm going to have to wait for the new pump kit. The one ear is definitely not as open as it should be. In the mean time I will take a closer look at the valve.

Trav-i. is pulling the nylon plug sketchy? I'd hate to screw this up, since finding a replacement might be tough. Did you tap the plug like the instructional said or did you figure another way?

[bollingball]

Surfin: Have you looked to see if the check valve is working or do you want to take it apart any way. Does the diaphragm have a tare in it You do know the new one may have a plugged mickey ear and still need to be opened up like the one you have now Some time they don't get punched out and come that way.I'm just trying to save you some money. I did the same thing but I have a spare now.

[SurfinBird]

I'm going to check the valve before I try and tear into it, whats a good way to confirm it's working or not? I didn't see any tears in the diaphragm and it seemed to work. i felt light puffs of air when I activated the pump when the carbs were off. I'm hoping the new one has the proper holes. Like I said the one hole felt like I made it with the nail and it wasn't a nice clean punch through. Plus, the rod is slightly bent and the boot is beat up, so a new one wouldn't hurt.

[bollingball]

Put the #2 carb back together don't forget the acc. oring or it will leak fill with fuel and pump by hand. If the rack is still together you will see fuel out of all four nozzles. You can use an exacto knife to open up mickey ear. If you make a holding fixture then you have both hands free. (both holes must be open) In one of my pic. you will see a small fuel bottle that is what I use to fill the carbs with fuel with a short length of fuel line.

            Ken

[TwoTired]

I had to drill the mickey mouse ear to same size as the hole in the body cavity, to get full accell pump flow.  The diaphragm part must be intact, though.

I have NEVER removed the nylon plugs for the two check valves.  They can both be cleaned and "proven" to function with pressurized carb cleaner.  They must block one direction, and flow freely the other direction of flow.  Wear safety goggles.

I've also gotten the system to function on the bench.  I just chucked it in the bench vise to gently hold it.

While the engine should run without the pump working, it should start easier with a couple squirts and choke applied.

Cheers,

[lrutt]

I know on my K8, the rubber diaphram should have had 2 holes in it I think. One for the fuel to reach the accel bowl. That hole was not in the rubber. Came from the factory like that and had NEVER worked. I punched a hole it in and bingo, all four posts were shooting fuel. Sure made a big difference in the running.

[Skunk Stripe]

I replaced my accel pump and it only had 1 hole and worked fine. Opening the second hole did not produce any noticeable change. So, I just left it with 2. So having a ragged hole will not really affect things as long as fuel moves.

[TwoTired]

It must be fun to live in a world where physics don't apply.   

[Trav-i]

Surfin,

Pulling the little plug if done CAREFULLY isn't too hard to do.  It's actually most likly brass (mine was)  Just be very careful drilling the plug.  I did it with a drill, but I highly recomend doing it with a pin vise, it will be easier to keep straight.  Once I had a small shallow spot in it i used a small screw and vise grips to pull the plug.  Just DON'T loose the spring and ball.  Then I cleaned it reinsatalled it and now it works perfectly.

Travis

[Skunk Stripe]

It sure is. Things work so much better. But like I said, my replacement pump had only 1 hole and it did work. You have to like it, you do not have to agree with it but work, it did.

[SurfinBird]

Ok, so I already had the bike in one piece and decided I might as well try and start it, since bollingball mentioned the pump wouldn't keep it from starting, before I pulled everything apart again. No big surprise when it didn't start, but, I think I confirmed that the accel pump isn't working. Tell me if my thinking is correct.

I turned on the tank, no fuel overflow, happy about that. I knew I had an overflow problem so I payed attention to where the fuel was coming from. I gave the throttle 20 or so good twists to see if I just didn't prime it the first time. I hit the starter and the usual, engine turning, not catching. Only 1 carb overflowed, #2, interesting. I'm thinking the valve is drawing fuel when I twist the throttle but not going out the posts, probably pumping the fuel back into the bowl (check valve? The bad mickey mouse ear hole?) and overflowing, not a large amount. What do you think?

A second question, bollingball, what else could have kept it from starting if it doesn't need the accel pump? I'm getting good spark and compression (don't know how good) and the plugs are dry, i know it's probably something in the carbs, what should I look for? I gave them a pretty good cleaning with guitar strings and carb cleaner.

[bollingball]

Try a can of starer fluid spray around the large slot at the bottom of the air box if it is still on if not spray the carbs if it tries to start then you know it is a fuel issue. make sure you have the kill sw, in the correct position.

              Ken

[SurfinBird]

I read I can use carb cleaner in place of starter fluid, would that work? Also, i've never tried it before. The air box is off, do I spray it directly into one of the carbs, or just near them?

[bollingball]

With air box off move the can across all four carbs while spraying it does not take a lot about 1 second in each one. If you have fire to the plugs it will kick over maybe even run you will hear it.

Carb cleaner may work starter fluid for sure. Hope this works so we can start narrowing this down

               Ken

[SurfinBird]

I got the new pump and the mickey ears have nice clean holes in them. At least this should fix my accel pump problem, now to get it to turn over. I haven't had a chance to try the carb cleaner start yet. I'll give it a try before I pull the carbs to replace the pump and check the valve.