z1000j3 carb setup

[marve114]

hi guys
ive got the standard 34mm cv carbs

need some info as i cant get at my manual

float heights
and mixture screw settings

so i can check
got the air screws at 1.3/4 turns out

i think the main jets are 117
and the idle jets have got a little plug with a lil o ring over them

just trying to get it to run nice

[Al]

Book says for UK J3;

Mains are 117.5R
Needle Y2
Type 5CF58
Needle position 3
Pilot 37.5
Starter jet 1:45 Jet 2 0.8
Main air 85
Pilot screw 2 turns out from fully closed.
Dynamic fuel level is 3 +- 1mm below body to float bowl flange
or 18.6 mm float height to flat portion of float from body to bowl mating flange with carb body upside down.

------------------------

Beneath that for Z1000R
127.5
Y4
5C48-3
2nd groove from top
37.5
1:45
85
Pilot screw 2 turns out from fully closed.
Dynamic fuel level is 3 +- 1mm below body to float bowl flange
or 18.6 mm float height to flat portion of float from body to bowl mating flange with carb body upside down.

------------------------

For range; i'm using standard air-box with K&N and free exhaust, Unitrak head and cams on 1170 HC pistons and made these changes;
Mains 130++ i think
Pilot screws are an average of 3 turns out (from 2 3/4 to 3 1/4)
I also use another spacer between the diaphragm spring and vacuum slide to slow the slide down a little.
Dynamic fuel level is 4 +- 1mm below float bowl to body mating surface with gasket removed.

Dyno says its near perfect fuelling through the range.

Hope this helps.

AL

[marve114]

at the moment it starts up fine on choke but hesitant to rev up and when it does it just burrs down and nearly stalls then comes back up to idle
just checked float height they at 20.1mm
going to drop them now
post back with progress

[skoda]

hello m8 i had the same problem with my z1100
turned out to be 2 blocked pilot jets! worth a look
if you have the carbs off

[Pigford]

at the moment it starts up fine on choke but hesitant to rev up and when it does it just burrs down and nearly stalls then comes back up to idle
just checked float height they at 20.1mm
going to drop them now
post back with progress

Yeah, makes sense, may be running a tad lean

[marve114]

After fart arseing about checked float height did that wound the air screws out still no joy sod them old cv carbs
dont know whats up with them

tried my dads 36mm fsr mikunis beautifull probally want setiing up a bit poped back trough the carbs once or twic but he wont let me have them so i will save all my pocket money and get my own set of smooth bores or such like
so wont be riding it any time soon

[marve114]

are the old original card spoes to have the plug over the pilots

[Al]

Original carbs have plug over the pilots.

After fart arseing about checked float height did that wound the air screws out still no joy sod them old cv carbs

Nothing wrong with CV's if they are clean inside




AL

[LTD Project]

Zorded

What does " Mains 130++ i think " mean some posts above?

I have gpz1100 B1engine with the k&n pod filters and custom exhaust, I thought it was around a 15% lift for each for these items so if standards for the 34mm CV carbs are 117.5 that makes around 152 for mains..... Am I barking up the wrong tree?

Also having problems at the moment where she starts first press of the button on full choke and high idles on this but just dies the moment I move it to half choke or less. Definitely won't do anything with the choke off completely.

Help please......

[Al]

What does " Mains 130++ i think " mean some posts above?

I think that should have said + - meaning that standard mikuni jets have a 10% plus or minus manufacturing tolerance for flow rate from that marked on the jet.
I tested mine and found greater than 10% error across the four. (Graduated water bottle, length of windscreen washer tube with jet screwed in the end and a stopwatch)

I reamed out the smaller ones to match the largest flow rate and what started out life as 127.5 all became around 130 give or take.
If you have two smallest and two largest the two largest need to be in the two centre pots!

The carb is a variable volume / fixed ratio instrument.
If you needed to go to 152 mains you would likely have to go up a bore size for the body or loose the stoichiometric ratio between fuel and air that they are designed to produce.

130 should be more than enough.

The idle problem for the bike will not be related to main jet size.
These bikes like a rich mixture to get going from stone cold and with CV's can take up to a couple of minutes on choke before they are happy.
If it pops and spits back through the carbs on start up even with choke they are set about right.

How many turns out are the fuel screws??
There is a mistake in the manual about the working of these screws.
Mine were about three turns then, and more like two turns now.
If they are more than 3 turns out from lightly seated then you will need to raise the level of fuel in the float chambers slightly by manipulating the float tangs.

Put a colour tune in it and set the mixture screws slightly to the rich side of the colour change transition indicated in the user instructions.
Colour tune is the cheapest source of useful information i think you can buy and if careful you can get a lot of hints about misfires / erratic running and half throttle mixture as well. Wear goggles for this part
If you cant detect the colour change transition from observation then youre carbs are at fault and either dirty or have mechanical issues.

AL

[LTD Project]

Al
Thanks for the detailed reply. Hopefully on with it tomorrow, so will let you know how I get on.

There is only one art darker than that of carb tuning and tweaking and that is electrckery!

Thanks again

[LTD Project]

Found this detail in Service supplement Manual for GPz1100 and Z1100R1

Specific to the Z1100R1 Mikuni BM34

Main Jet No. 1 130
Main Jet No. 2 135
Main Jet No. 3 135
Main Jet No. 4 130

No I know that I have BS34 Carbs from J model I presume, but why would the two middle carbs have larger main jets?

Should I try to emulate this on my 1100 engine?

Also I have little brass jets screwed into the holes of the face that point towards the air cleaners at about 4 o'clock if you looked end on. Don't see these in any manual pics, parts diagrams etc relating to either the J or the 1100R1 mentioned above. Anyone know what these are, whether they should be there?

[Ginger Bear]

Also I have little brass jets screwed into the holes of the face that point towards the air cleaners at about 4 o'clock if you looked end on. Don't see these in any manual pics, parts diagrams etc relating to either the J or the 1100R1 mentioned above. Anyone know what these are, whether they should be there?

These will be after market 'air corrector' jets which were probably fitted when the airbox was lost.

[LTD Project]

Ok Steve, thanks, do you mean like a stage 3 dynojet kit?

If this is fitted can I expect to find non-mikuni non standard size jets else where too?

[Al]

Screwed in jets see this one from earlier

http://www.z1ownersclub.co.uk/forum/vie ... sc&start=0

The reason for the different size mains was because the two centre cylinders run hotter and therefore weaker, they tried to off set this by cooling them with an excess of fuel.

Tried this for a while on the J and found it not to make any significant difference.
If you have weakness in the two centre pots (witness lighter colour on those plugs) when all four carbs are set the same then try it out and see what happens.
I found it easier to lift the needles on the two centre cylinders half a notch with the microscopic washers you get from the dynojet kits.

AL