Topic: Carb accelerator pump issue

[OrganDonor]

Pretty sure I've got a problem with this - and found today that replacement parts are not available so I've got to make due with what I've got unless someone out there knows where to go?  The bike is a 1980 650 Custom.  The parts "seem" to be OK, so maybe I'll get lucky and cleaning will work...

Are there supposed to be any one-way valves to ensure fuel goes in one direction (there are only brass inserts), or is the pump self-priming from the carb vacuum? And if self-priming how can one test the pump functionality on the bench prior to re-installing?  After cleaning I can fill the bowl and prime the pump by holding my finger over the exit port during the pump back-stroke after which it would squirt pretty good once or twice.  But without my finger over the hole between strokes it loses pressure. I cannot get the pump to push gas through the jets - am I cooked?

[Spanner 1]

There's 2 check valves in the small acc. pump sump below the  ( Mickey ears thingy! ).
First one is down the very bottom and the 2nd. one is vi sable below one 'ear'..... either one blocked/stuck + no squirt. Seems bottom one gets stuck/rusted first. try soak the piece in carb cleaner . Little ball bearing in there might free-up.

[theofam]

Yep, what Spanner says.  There's also a check valve in the top of the carb bowl where the accelerator pump's fuel gets pulled through.  In addition to Spanner's suggestion, I'd waste a can of carb cleaner trying to blow it out, too!  Both of mine were plugged badly.  Let each sit in carb cleaner for an hour and try to blow carb cleaner through them.  At first, they'll trickle - that's not enough.  You want it to shoot out from around the little gold-colored squares (behind which are the check valve balls that get gummed up).

Hope that makes sense.  I thought I had cleaned my carbs well, but my accelerator pump wasn't working until two days ago whenI did the above.

[theofam]

One clarification, I'm not familiar with your carbs, so I'm making an assumption they're constructed similarly to my 78 750K's PD42Bs. 

Another thing I missed that'll help is the carb bowl's check valve likely needs an o-ring to seal it with the carb body.  If you don't have it installed, the accelerator pump will lose pressure due to it not sealing.  Instead, it'll squirt all over your airbox (a lesson I learned today)!

Good news is you're likely close to having a much better running scoot!

[OrganDonor]

Thanks guys this is extremely helpful.  Now that I know the mechanism within the pump it'll make it much easier to both fix and test.  I was working blind!

[Outboardbill]

Check out hondachopper.com technical library.  It gives the entire procedure with pictures for cleaning the accelerator pump valve.  I had to do the same to mine since it had been sitting for 15 years.

[Hush]

Everything the guys below said, the best test is to pump the rod up and down with your finger and the bowl full of gas, it should shoot for quite a distance across the garage.

[OrganDonor]

Just a note to thank you guys for the help - I soaked the bowl and pump base in carb cleaner (twice) that was that.  It was obvious from the pumping action it was fixed.  Like Hush said, the pump squirted gas across the garage and easily through the jets.  I installed the carbs last night and the bike runs great!  You guys saved me a lot of poking around and head-scratching time.  To the road!