Accelerator pump not pumping

Take both plastic arms off, that way then neither will work and your throttle will be lighter..havent used them for years with no issues.

The pump jet in bowl is next to the one with the Oring fitted to it, well at least there should be an O ring though if you leave the Oring off the choke not sure it has that much affect as have seen the dodgy and missing alltogether yet the chokes still work !!

However if one must have them working then firstly unscrew the nozzle where it screws into the side of the carb and make sure it is clear and not blocked. With it removed and lifting the slide do you any fluid at all here.
If all the passages are clear, the diaphragm is not old and cracked then it should work, If not then  you need to simply prime the system as Cam suggests. Remove the screw in valve from the pump itself.. the part which is held on with three screws, make sure there is no crud there and the channel down to the nozzle is not blocked.

Good Luck  (bigthumb)


 
I overhaul a fair number of PHF/M carbs, for Laverda twins and triples, and the occasional Guzzi, BMW and Ducati.  I have given up with re-using the jets and valves of the accelerator pump circuit.  The amount of time I have spent trying to get the things to work with used items just cannot be justified.  If the diaphragms are supple, these can be re-used, but the brass bits are discarded, regardless of external condition.  The saving on labour far out-weighs the cost of additional parts.  Works each and every time, the pump rarely requires priming to get the juice flowing.

piet
 
thanks Piet. So, if the pump is not pumping then you just change all of the brass fittings?
So, I am pretty sure I can check that the starting jet, the mains and pilot jets and the float valve are clean & serviceable. That leaves me with the pump jet and the inlet valve?
Do you think I need to bring the mains jets back to the factory 115? As far as I can see it is a standard engine re exhaust and airbox.
 
tobster said:
thanks Piet. So, if the pump is not pumping then you just change all of the brass fittings?
So, I am pretty sure I can check that the starting jet, the mains and pilot jets and the float valve are clean & serviceable. That leaves me with the pump jet and the inlet valve?
Do you think I need to bring the mains jets back to the factory 115? As far as I can see it is a standard engine re exhaust and airbox.
Click to expand...

That's exactly wot I wrote... :D  But the diaphragm has to be in usable condition!

Clean does not necessarily mean servicable.  I've seen lots of totally shagged carbs that were clean as a whistle...

Choke jet rarely needs to be replaced, it is so large it takes a lot of crap to close it up.  Mains and idle jets can suffer from corrosion if the carb has stood for any lengthy period and the fuel has evaporated or moisture has ingressed.  If they are gummed up with old fuel, they are discarded as well.  Needle jets and needles are always replaced, regardless of external condition.  You never know how old they really are, and are 2 of the most important items in keeping the carb working correctly.  Float valves need to be checked in regard to plunger position, float heights precisely adjusted.  Slight wear on the slides can be tolerated, but if an arc starts to appear at the bottom end of the engine side, it's time for the bin.

It's not a cheap proposition getting these carbs back to scratch, and an overhauled carb will not perform as long and well as a new one due to wear in the body itself, but it will be quite satisfactory for at least another 40-50K km.

When working on an unknown engine, I always revert to stock carb settings for a starting point and go from there.

piet
 
I run 132 mains on a 1971 SF with 2 into 1, less restrictive pipes, where the Breganzie Stk main jets where 125's with their 2 into 2 DMC's.

Don't lean out your mixture under load - Better to be rich then to lean out and hole a piston.

This applies to just about any carburated ingested engine.
 
As I come from a two stroke background I'm all for a little jetting safety margin, perhaps a size richer, BUT running a 132 when a 115 is specfied by the manufacturer seems like a mighty big safety margin (15%) (and will surely compromise performance???). AND in my experience with Japanese manufaturers they all tend to jet rich anyway, so i see no reason why Italian ones wouldn't do too.  Anyway 115 jets ordered :D - plug chop time!!!
 
tobster said:
Do you think I need to bring the mains jets back to the factory 115? As far as I can see it is a standard engine re exhaust and airbox.
Click to expand...

phil37 said:
If you're still using the megaphone type "silencers" - be careful not to go down too small - regards - Phil
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tobster said:
thanks Phil, yes the're still fitted. Will that make a big differnece?
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Thought it was an Alpino... ??? ::)

Did you poms stick those horridly ant-social exhausts to every 500 that reached the shores of Blighty?

piet
 
this bike actually came from your adopted homeland. Perhaps that is why it got exported as it was just toooo loud for Germany  :LOL:
 
tobster said:
this bike actually came from your adopted homeland. Perhaps that is why it got exported as it was just toooo loud for Germany  :LOL:
Click to expand...

Then I'm glad that you guys now have to bear the racket! :D

Have I ever mentioned that I don't particularly like excessively loud bikes?

piet
 
update - I took the carb float bowl off and squirted some fuel through the inlet valve while pressing the accelerator pump (AP) and fuel eventually started to come out the pump jet!!! I reinstalled the carb and the AP works now!! I guess I primed the system (as suggested by many). I assume it will still be primed when i go back to it as the inlet valve will stop the fuel draining back (assuming the inlet valve is still a valve of course).
Thanks for all your input/help. Now to see how well it runs with 115 jets....
C2
 
Tobi, no intention to spoil your success, but be prepared that it'll stop working again soon. Just the same as happened with one of my triple carbs :( Would recommend to test the amount of fuel squirted after 20 full strokes of the throttle, should be even on both carbs, don't know the exact quantity for the small twins, though. The AP might even stop working already during that test.

Needs only a bit of fuel to evaporate out the jet during some resting time and the defective check valve resting in the pump housing starts to suck air in. From then on it might take a bit of throttle activity before it entirely stops squirting, but it will happen. Highly recommended to replace that valve.
 
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