Accelerator Pump problem

[robsgreen]

Ive just managed to finally get my carbs to stop leaking from the float needle valves ( see my previous threads)and thought I would just test the Accelerator pump whilst they were still connected to the fuel supply. When I open and close the throttle, nothing comes out of the jets in the intake funnels. When I had tried them previously they squirted fuel from each nozzle everytime a manually opened the throttle. The only difference from the last time is that I have adjusted the Accelerator lever to give 3mm at one end and .05mm cleareance at the other end acting on the pump rod, as per the manual. When the throttle is opened, the Accelerator pump rod moves about 1-2mm, is this OK? The pump rubber has been replaced. I took this off and squirted some carb cleaner into the feed hole that supply the bank of nozzles and all jets ran clear. When I took off the cover and removed the rubber seal and rod, the chamber was full of fuel. I am I right in thinking that the fuel pipes that supply the accelerator pump nozzles is primed by the main fuel supply and the accelerator pump supply just creates the pressure in that system to squirt the fuel? Could there be an air lock. Any help really appreciated. I think my carbs are trying their hardest, not to get fitted into my bike so I cant start the engine!

Regards
Martin

[daves79x]

Set the pump rod with no clearance, but not holding the rod down at all. I like to see 2 or 3 mm of stroke. Often, on a dry system, it takes a while to prime. Take a needle-nose plier and grasp the pump shaft and manually stroke it it's full amount (oh, this doesn't sound good). You'll get it primed and fuel will start squirting. The pump gets it's fuel from the #3 bowl it's attached to. Check for leaks also around the pump body when you are testing the pump. Sometimes they are hard to seal.

Dave

[robsgreen]

Thanks for that Dave. Ive managed to get 3 mm now and this will hopefully do the trick. It actually sounds like its doing something now. Is there anything to look out for regarding the two valves in the float bowl?
Regards
Martin

[daves79x]

Martin: Not sure I understand our question about the 'two valves' Could you try again?

When your bowls are filled and you are wet testing, you should be able to get the accelerator pumps to squirt a big shot right down the carb throat when the bell crank is given a quick flick. Yes, you will hear the air coming out of the circuit, but then make sure all 6 squirt before reinstalling them.

Dave

[spencer]

I think the two valves are the two check valves which control how the pump works. One lets fuel in, and another one lets fuel out.

[herdygerdy]

And make sure you remember to install the small separate O ring onto the accelerator pump body before securing it onto the float bowl.

Even tho' I have now done many sets, it is often "a long time between drinks" and I had forgotten this important little critter. Symptoms were fuel escaping from around float bowl in the area of the accelerator pump body when the throttle was opened vigorously with the bowls full.

Thus (and fortunately for me) amply demonstrating the importance of doing as much testing on the bench as possible and diagnosing issues found BEFORE installing them

While you can (& ack you may have done this already), but take the time to set your float levels to as close to 15.5 mm as possible. I use a small engineers steel ruler to do this, with the carb lying on its side just off from vertical so the tang on the float is just ever so slightly just 'kissing' the tip of the float valve needle. You don't want gravity pulling the float down and depressing the tip of the needle thereby giving you a false reading.

And +1 on being checking to be sure all accelerator pump nozzles fire happily before installation back on the bike. Also not a bad idea to fill bowls and leave a bit extra in a clear tube used to fill the carbs. Mark the level and leave it overnight. Goal is for there to be no leaks at all.

And finally, get the benefits of all your hard work on your carbs for years to come by installing a decent in line fuel filter before even thinking about connecting it to your fuel tank, no matter how clean you think it may be inside.

Good luck, keep at it, you will be well rewarded. Enjoy the journey.

Cheers..Tony