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Carb Jetting

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crossthread
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Carb Jetting

#1 PostAuthor: crossthread » Mon Jun 10, 2019 11:53 am

Gentlemen , advice please. Bike is a 1980 Rickman with a 1979 Mk 2 Z 1000 engine . Originally supplied to Germany , which may or may not be relevant. Carbs are 28 's non - pumper standards. Original jetting was as per Canadian models , I can't find info on German models . 4 into 1 and pod filters. When I got it the bike was virtually a non-runner with carb problems . Cleaning and re-jetting improved matters , I went from 105 main to 112.5 , and 15 pilot to 17.5 pilot. All good with only a stumble off tickover . I have just fitted air correctors which have now cured the stumble / hiccough. Bike runs faultless , no coughs , spits , backfires or missing. HOWEVER , now to the question . All this works with the air screws open 2 turns , I believe ideal is 1 1/2 open . What does this say about my jetting ? Or is 2 turns OK ?

kev edwards
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Re: Carb Jetting

#2 PostAuthor: kev edwards » Mon Jun 10, 2019 2:08 pm

As you have pods, after market exhaust and air corrector jets probably means you have it in the ball park for your set up, really need to get it on a dyno now to get the fine tuning done.

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zed1015
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Re: Carb Jetting

#3 PostAuthor: zed1015 » Mon Jun 10, 2019 2:58 pm

Usual range is 1-1/4 to 1-3/4 so you are not too far out at 2 turns but this shows you may be a little rich on the pilot and may need to go back to the 15 and retune the air screws down a little.
The main thing is having the mix ratio correct which you probably have at 2 turns with that 17.5.
As long as it runs ok it will be fine but if you want to be by the book in the 1-1/2 turn range then drop the pilot although the bike should run just the same.

weaver
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Re: Carb Jetting

#4 PostAuthor: weaver » Mon Jun 10, 2019 3:14 pm

if its running well and the plugs are the right colour I would leave well alone :wink:

Julian_Boolean
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Re: Carb Jetting

#5 PostAuthor: Julian_Boolean » Tue Jun 11, 2019 8:00 am

weaver wrote:if its running well and the plugs are the right colour I would leave well alone :wink:


This, if it isn't broke, don't fix it.
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Ultim8pc
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Re: Carb Jetting

#6 PostAuthor: Ultim8pc » Tue Jun 11, 2019 8:32 am

weaver wrote:if its running well and the plugs are the right colour I would leave well alone :wink:

+1 for that statement
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crossthread
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Re: Carb Jetting

#7 PostAuthor: crossthread » Tue Jun 11, 2019 9:11 am

Thanks Guys , some times I am my own worst enemy and don't know when to stop . Being a perfectionist can be a pain . :D :D

needaz1100r
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Re: Carb Jetting

#8 PostAuthor: needaz1100r » Tue Jun 11, 2019 2:12 pm

weaver wrote:if its running well and the plugs are the right colour I would leave well alone :wink:


+3 on this, the screw is there to adjust to get the right mixture. The right mixture is the criteria, not the position of the screw.
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johny brando
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Re: Carb Jetting

#9 PostAuthor: johny brando » Thu Jun 13, 2019 7:33 am

zed1015 wrote:Usual range is 1-1/4 to 1-3/4 so you are not too far out at 2 turns but this shows you may be a little rich on the pilot and may need to go back to the 15 and retune the air screws down a little.
The main thing is having the mix ratio correct which you probably have at 2 turns with that 17.5.
As long as it runs ok it will be fine but if you want to be by the book in the 1-1/2 turn range then drop the pilot although the bike should run just the same.


+1 to Robs advice, as usual he's spot on . All (.... or most ) 28mm Carbs Z1000 carbs are set up OEM with 15 pilots - which are incedently running all the time ( not just on idle as most people think !!! ) there is just ONE & HALF thou i/d difference between a 17.5 pilot bore & a 15 pilot bore..... but it makes a real difference . To prove that fact leave the air stew at 1 & quarter turns out & put a set of vacuum gauges and register the difference in Ventura draw / vacuum between the 2 different yet close jet sizes & you'll see thats a fact !!!!!!!! & also with your air screw wound out too far for compensation you vacuum plumits.
Air corrector jets should be about .7's no bigger . Cheers.


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