KZ650H1 carb missing part

Hi all.

I removed the carbs from my KZ650 H1 (CSR) to rebuild and clean. The first thing I noticed was a missing part from the accelerator pump. I have highlighted in a picture. I believe that this should house a diaphragm but I am not really sure what difference this makes or where to get this particular part. Any suggestions on either what effect not having this will cause and also if I really need it should I try to get the part or am I better to replace these carbs with a different model?

Thanks in advance.
Dave.

There are two types of accelerator pumps. MOST KZ650 have a triangle shaped cover that fits over the place you indicate with a spring and diaphragm beneath the cover. On your assembly, there is no hole down on the bottom of the cover in the circle part so you have the type that doesn't use the 2nd diaphragm... only a single stage pump so they never installed the triangle shaped cover. In other words, nothing is missing.

Wow George! As always you have the knowledge....... Very grateful for the reply but it does bring up a question.

Was there any advantage to the accelerator pump with the 2nd diaphragm?

Honestly, there is no advantage to having an accelerator pump at all. I believe that the 2nd diaphragm cuts off air when the throttle is shut. I am not positive. The accelerator pump was put on a number of Kaw models in 1979... KZ650 and KZ1000. If you look at the jetting on the A2 models; especially the KZ1000A2A you can see some inherent problems with leanness. I suspect Kaw didn't want to richen the idle mixture to get through whatever EPA standard was set at the time... I suspect one of the tests was emission output at idle. Anyway, The bike can idle away all day with the very large slide cut out, very small needle jet and lean jet needle and #15 pilot jet. Problem is, at some point, somebody has to ride the thing and the first thing you do is TAKE OFF from a stop. The lean setting on the pilot mixture screw ensured that the bike would boggggggg... you would have to rev the engine quite a bit to make it move especially when not fully warmed. I guess that since Kaw would not want to put in writing that you had to ride around on choke for 15 minutes (very rich mixture and the smog police might read this), they stuck the pump on. ONE squirt of gas as the throttle is opened. It helps in the mid-range where the jet needle/needle jet combo is similarly lean. The pump made the bike rideable.

Just like any other band-aid type fix, there are better ways around the issue. We probably convert 50 sets of pumper carbs a year to non-pumper at the owners request. Why? The pump has VERY VERY VERY small fuel pickup hole in the bottom of #2 carb. Then it goes through a check valve. Guess what happens if the bike sits for a few weeks? Gas goo in the little hole and the valve. It is tough to clear. The atomizing holes in the pump nozzles in the carb venturis are also in need of checking EVERY time you turn around. They are small and you can't poke a wire through them. They are hard to clear.

OK... what happens when the pump quits pumping? In lean bog and poor performance show its ugly face. The secret is to get rid of the pump system (change bowls) and rejet properly. I won't go into how to rejet as there are a number of different situations as far as airbox/pipes/mods and carb models that make a one-rejet-tip-fits-all answer kind of hard to come up with.

Clean that bare spot on the bottom good and look for a brass bb inserted into the hole. If you drill out the bb, you can convert the single pump to double but you would need the missing cover and the other diaphragm and spring. Now some of this stuff I noted is conjecture... a best guess based on memory of the time (late 70s), knowledge of the industry and some guesses. I could be wrong on some of the facts but that is how I see it. I am glad the EPA police did there job. I remember playing golf out on Haynes point in 1976 and hitting the ball in the air and not being able to see the ball for all the yellow emissions smog in the air. The air is definitely cleaner now!

wg i have this same carb setup on my '79 kz650 with the pump how would i rejet with pod filters and a 4-1. my jets are currently 112.5 if i changed bowls to a non-pumper?

Gee, I am not sure. Good luck... it will be a good chance to learn I guess.