Hello Guest User,

Please feel free to have a look around the forum but be aware that as an unregistered guest you can't see all of it and you can't post.

To access these 'Registered Users Only' areas simply register and login.

Carb Jetting

Need help restoring, building, or finding then try here.

Moderators: chrisu, paul doran, Taffus, KeithZ1R

Message
Author
crossthread
Regular Poster
Posts: 69
Joined: 15th Oct 2017
Location: Devon

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
Hardcore
Hardcore
Posts: 2051
Joined: 3rd Apr 2009
Location: leverington UK

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.

User avatar
zed1015
Hardcore
Hardcore
Posts: 3798
Joined: 2nd Nov 2005
Location: Somewhere between Scunny and Goole.

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
Custard Cream
Custard Cream
Posts: 759
Joined: 15th Nov 2011
Location: merseyside

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
Custard Cream
Custard Cream
Posts: 804
Joined: 20th Oct 2016
Location: Ipswich

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.
An expanding collection of parts pretending to be a Z1100R and a Yamaha FZ750

User avatar
Ultim8pc
Hardcore
Hardcore
Posts: 2132
Joined: 5th Sep 2014
Location: Keighley, West yorkshire
Contact:

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
http://www.airevalleyclassics.co.uk
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.

crossthread
Regular Poster
Posts: 69
Joined: 15th Oct 2017
Location: Devon

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
ZedHead
ZedHead
Posts: 1128
Joined: 11th Sep 2012
Location: Reading
Contact:

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.
Cheers,

Mark.

johny brando
100Club
100Club
Posts: 303
Joined: 3rd Aug 2013
Location: Australia

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.


Return to “Bike Help”

Who is online

Users browsing this forum: No registered users and 56 guests