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Carb Jetting
Moderators: paul doran, Taffus, KeithZ1R, chrisu
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- Regular Poster
- Posts: 69
- Joined: 15th Oct 2017
- Location: Devon
Carb Jetting
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 ?
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- Hardcore
- Posts: 2051
- Joined: 3rd Apr 2009
- Location: leverington UK
Re: Carb Jetting
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.
Re: Carb Jetting
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.
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.
Re: Carb Jetting
if its running well and the plugs are the right colour I would leave well alone
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- Custard Cream
- Posts: 804
- Joined: 20th Oct 2016
- Location: Ipswich
Re: Carb Jetting
weaver wrote:if its running well and the plugs are the right colour I would leave well alone
This, if it isn't broke, don't fix it.
An expanding collection of parts pretending to be a Z1100R and a Yamaha FZ750
Re: Carb Jetting
weaver wrote:if its running well and the plugs are the right colour I would leave well alone
+1 for that statement
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Keyster rebuild kits & carburettor spares - airscrews, jets, needles, starter plungers & gaskets.
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10% discount code Z1OCTEN
Keyster rebuild kits & carburettor spares - airscrews, jets, needles, starter plungers & gaskets.
Also petrol/ethanol proof float bowl gaskets. IMD pistons preferred seller.
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- Regular Poster
- Posts: 69
- Joined: 15th Oct 2017
- Location: Devon
Re: Carb Jetting
Thanks Guys , some times I am my own worst enemy and don't know when to stop . Being a perfectionist can be a pain .
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- ZedHead
- Posts: 1128
- Joined: 11th Sep 2012
- Location: Reading
- Contact:
Re: Carb Jetting
weaver wrote:if its running well and the plugs are the right colour I would leave well alone
+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.
Cheers,
Mark.
Mark.
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- 100Club
- Posts: 303
- Joined: 3rd Aug 2013
- Location: Australia
Re: Carb Jetting
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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