VM24SS Pilot extenders

kimchella
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VM24SS Pilot extenders

08 Jan 2025 12:32

Hi Guys, does anyone have any used/new pilot jet extender for sale? I know they are not available anymore, and they are not necessary for the carbs, but thought I would ask. I have just started the bike today, for the first time since fitting the carbs back. A good learning curve setting them up, and the different jets fitted to the early B1s. This one has 2 pilot jets, an outer one number 50, and a inner one number 15. It is ticking over ok and revs nicely, just need to get a colour tune now to set the mixtures.

Many thanks all,

Rich.

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Injected
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Re: VM24SS Pilot extenders

08 Jan 2025 13:13

#907625

You can get rid of the 50's as they don't do anything, redundant in my eyes. Nobody can see them or even know there missing.

I have never heard of anybody running them, just something else to plug up with gas tarnish.

1978 KZ650B2 w 1197cc Z1 engine
1977 KZ650B1 w 750cc Spectre engine
1979 KZ650C3 w 831cc Hot Rod engine
1978 KZ650C2 w 762cc DFI project
1977 KZ650C1 stock restoration project
1978 KZ650B2 modified project
1978 KZ650B2 Injected Drag 831cc
1980 Z1 Custom Frame Drag 1327cc
1981 Z50R Honda tow bike

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Warren3200gt
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Re: VM24SS Pilot extenders

08 Jan 2025 14:05 - 08 Jan 2025 14:07

#907626

I don't know how true it is but the apparent reason they were ever fitted was to create a small reservoir of fuel
between the 50 jet and the pilot jet.
This was an interim solution to US emissions regs. It was required due to the air fuel mix being set very very lean to pass the regs which caused a virtual engine cut out on throttle close gear changes.
Subsequently the issue was resolved by the introduction of pumper carbs which achieved the same effect in a more controlled way.

(all allegedly !!!!) I've yet to hear of a more plausible explanation.

Z1000J2 somewhat modified!

Last edit: 08 Jan 2025 14:07 by Warren3200gt.

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gd4now
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Denco where did you go?
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Re: VM24SS Pilot extenders

08 Jan 2025 15:18 - 08 Jan 2025 15:20

#907631

From info I could find it appears that only the vm24 and vm22 carbs that came stock (on some of the 650s) which have only a pilot screw (not air screw or both air and pilot screw) came stock with the 50 jet over the 15 pilot jet. As stated I have removed them from both 22s and 24s and did not notice any difference with or without them. But that is just me. I do not claim to know why the 50 jet was used or why only on non-air screw sets? The suggestion given makes as much sense as any other I have thought of or heard.

As to the extenders, no I tend to toss them when I run across them. Will say I have not seen any in a very long time. There appears to be some members here who do have lots of carbs and parts.

1977 KZ650 B1
Pods and Denco header

OLD KAW OWNERS SMILE ALOT

Last edit: 08 Jan 2025 15:20 by gd4now.

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Re: VM24SS Pilot extenders

08 Jan 2025 20:19 - 08 Jan 2025 20:25

#907640

wrote:

From info I could find it appears that only the vm24 and vm22 carbs that came stock (on some of the 650s) which have only a pilot screw (not air screw or both air and pilot screw) came stock with the 50 jet over the 15 pilot jet. As stated I have removed them from both 22s and 24s and did not notice any difference with or without them. But that is just me. I do not claim to know why the 50 jet was used or why only on non-air screw sets? The suggestion given makes as much sense as any other I have thought of or heard.

As to the extenders, no I tend to toss them when I run across them. Will say I have not seen any in a very long time. There appears to be some members here who do have lots of carbs and parts.

It was 650Ed who advocated tossing the #50 jets, he was very vocal every time it came up. Both he and I have '77 C1's, mine is Canadian version and his a USA version. We never had pollution controls till much later in Canada, so my carbs do not have them, and yes they are the air screw type.

With fuel screws you probably have more capability to richen the idle greater than with the air screws - not sure. My only experience with fuel screws is with RS/TM flat slides and CVK carbs.

1978 KZ650B2 w 1197cc Z1 engine
1977 KZ650B1 w 750cc Spectre engine
1979 KZ650C3 w 831cc Hot Rod engine
1978 KZ650C2 w 762cc DFI project
1977 KZ650C1 stock restoration project
1978 KZ650B2 modified project
1978 KZ650B2 Injected Drag 831cc
1980 Z1 Custom Frame Drag 1327cc
1981 Z50R Honda tow bike

Last edit: 08 Jan 2025 20:25 by Injected. Reason: info

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kimchella
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Re: VM24SS Pilot extenders

09 Jan 2025 09:25 - 10 Jan 2025 09:16

#907667

Hi, and thanks for your info. This bike is a 1976b1, which was sold in California beginning of October 1976, frame number 225.
It does seem to make sense for the emissions, and would be interesting to find out if these were only fitted to just the American market that had to pass the emission controls, or fitted anywhere else in the world that didn’t have these emission controls.
Thanks all,
Rich.

Last edit: 10 Jan 2025 09:16 by kimchella.

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