Pumper Carb Help

[Swiss Gaz]

Hi all, I have never got my USA import 1980 Z1000 B4 LTD to idle right but once off the pilot jets it goes like stink. I have gone back to basics with new #15 pilot jets and 102.5 main and needles. There are no air leaks and the air suction gubbins is all in place. However, according to the Clymer manual for my model the pumper arm lever is supposed to have approx 10.8mm thread exposed after the nut. There is no way this is possible without pulling the valve fully open. Also, on my bike should there be a check valve with three screws? Its missing and what is there looks all capped off. Included in the rebuild kit I got a new diaphragm for it in addition to the pumper diaphragm but there is nowhere for it to go. I have added a photo (hopefully!) Thanks,

[warren3200gt]

Are you sure you want to keep it connected as you've gone to non pumper vm's jets. Hopefully genuine jets not ebay crap.
Just disconnect the actuator arm and they'll behave like non pumper vm's.

[Swiss Gaz]

Thanks for the reply. I thought #15 and 102.5 are the stock jets for the pumper carb setup for that year and model of bike with the emissions paraphernalia . Its what the bike originally came to me with, so is this not right? Maybe its why I cant get it setup right.

[warren3200gt]

Not entirely 100% but I thought pumpers had 15 pilots and either 97.5 or 100 mains depending on where its from.
Whole theory behind pumper was to reduce emissions for US regs by squirting a bit of fuel to cover the lean spot between closing and opening the throttle caused by smaller jets.
I know 100% on Vm24 for 650's the above is true.

[zed1015]

Also, on my bike should there be a check valve with three screws? Its missing and what is there looks all capped off. Included in the rebuild kit I got a new diaphragm for it in addition to the pumper diaphragm but there is nowhere for it to go. I have added a photo (hopefully!) Thanks,

Which size carbs do you have ?
They should be VM28's and have the triangular sensor diaphragm casting unmachined and not functional..
If they are VM26's they will have the casting drilled and it will need blocking off if you don't have the cap etc.

[Swiss Gaz]

Hi, Yes, they are VM28s. What you see in the picture is the bottom of carb #2. I am assuming there was never a check valve fitted as there is no hole down the centre of where the check valve diaphragm pin would fit so I am assuming that's how it came from the factory. Its the 10.8mm setup on the pumper arm that has me scratching my head. I cant believe Clymer manual is correct right. 4mm looks more like what it needs to be. I am thinking this is just a red herring to my idling problems.

[zed1015]

Hi, Yes, they are VM28s. What you see in the picture is the bottom of carb #2. I am assuming there was never a check valve fitted as there is no hole down the centre of where the check valve diaphragm pin would fit so I am assuming that's how it came from the factory.

Yes! The 28's used the same bowl casting but unmachined and no valve etc because they didn't employ the triangular sensor diaphragm..