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.

Carbs on an 1100 Unitrack engine

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

Moderators: paul doran, Taffus, KeithZ1R, chrisu

Message
Author
Roger Hill
100Club
100Club
Posts: 157
Joined: 1st Sep 2008
Location: Nottingham

Carbs on an 1100 Unitrack engine

#1 PostAuthor: Roger Hill » Tue Jan 07, 2020 11:01 am

Hope someone has already tried this and has some base settings /advice please
Any help/advice on jetting/set up target settings from anyone out there who has fitted a set of 34mm Mikuni CV diaphragm carbs to replace the injection system on a GPZ1100A Unitrack motor.
I am using an 1100 shaft standard Kawasaki air box, stock GPZ1100 A Unitrack motor with 4 in to 1 exhaust with road legal silencer.
I have started at 140 main jets 4.0 pilots 4CG15 jet needles .
I am not looking for maximum flat out power more a decent spread of power and not fussy to use on the road.
Fingers crossed
Thanks
Roger Hill

User avatar
zed1015
Hardcore
Hardcore
Posts: 2826
Joined: 2nd Nov 2005
Location: Somewhere between Scunny and Goole.

Re: Carbs on an 1100 Unitrack engine

#2 PostAuthor: zed1015 » Tue Jan 07, 2020 11:07 am

I haven't got the specific specs but look at the stock jetting for the z1100r or the 1000J and go up on the main slightly.
The 1100 motors, spectre etc are also very close to the Unitrack including using the bathtub head but with shim over valve adjustment.
Last edited by zed1015 on Tue Jan 07, 2020 11:47 am, edited 2 times in total.

Julian_Boolean
Custard Cream
Custard Cream
Posts: 740
Joined: 20th Oct 2016
Location: Ipswich

Re: Carbs on an 1100 Unitrack engine

#3 PostAuthor: Julian_Boolean » Tue Jan 07, 2020 11:30 am

Z1100R jetting should work, as they have a Unitrak engine and BST34 carbs.
An expanding collection of parts pretending to be a Z1100R and a Yamaha FZ750

User avatar
Al
Hardcore
Hardcore
Posts: 2346
Joined: 21st Oct 2007
Location: Farnbronx, Sin City, N.E. Hants

Re: Carbs on an 1100 Unitrack engine

#4 PostAuthor: Al » Tue Jan 07, 2020 6:42 pm

Main jets for the 1984 1100R1in factory manual dated 1988 are;
Cylinders 1 & 4 130
Cylinders 2 & 3 135
With a restrictive exhaust and a standard air filter i would go with those based on modern flame proof petrols.
With a less restrictive exhaust and a single K&N air filter in the box; 135 and 137.5 respectively
I had best results with 130 and 132.5 respectively with a set up designed for the track and with the needles raised by 1 notch on the middle two pots.

Are they J carbs with the coasting enricheners? If so they will have a three pointed cover held on by three screws with a central grub screw and lock nut sticking out.
If so it may help to lower the needles on the two outer pots by one notch!
140 is not a bad place to start though and it wont be running weak which of course would be not ideal.
B9ES plugs as well.

AL
1981 J1

Roger Hill
100Club
100Club
Posts: 157
Joined: 1st Sep 2008
Location: Nottingham

Re: Carbs on an 1100 Unitrack engine

#5 PostAuthor: Roger Hill » Tue Jan 07, 2020 11:10 pm

Thanks to everyone who has replied so far.
I am a long way short of firing the thing up yet but have managed to convince my mates to get involved as it has stood as an abandoned project for the last three years.
Its slowly coming together now and I am just sorting out the carbs.
The carb castings are 34mn z750 (originally black factory finish with black plastic tops )they have been stripped to bare castings and ultrasonic cleaned and reassembled on to newly replated mount rails .
The internals have been replaced with slides,jet holder tubes ,Jet needles etc from a set of 34mm Mikunis that were damaged.
they have the Kawasaki choke mechanism not Suz**I so were from one of the 1000/1100 models .
I have fitted new pilot jets .O rings gaskets float needles and seats the diaphragms are all good.
Hope to have it making smoke and noise by Easter (ish) the rate its going.
Good call on the 1100R spec Al I will steer towards that set up once it is running.
Once again thanks to everyone who has taken the time to reply.
I will let you know how its going in a few weeks.
Roger Hill

Julian_Boolean
Custard Cream
Custard Cream
Posts: 740
Joined: 20th Oct 2016
Location: Ipswich

Re: Carbs on an 1100 Unitrack engine

#6 PostAuthor: Julian_Boolean » Wed Jan 08, 2020 8:45 am

Some Z750s and GPZ750s had BST34s, so they might be standard 750 carbs.
An expanding collection of parts pretending to be a Z1100R and a Yamaha FZ750

stephensmethurst
new poster
Posts: 5
Joined: 22nd Oct 2018
Location: Salford

Re: Carbs on an 1100 Unitrack engine

#7 PostAuthor: stephensmethurst » Thu Jan 09, 2020 5:43 pm

Fitting appropriate jets is sound advice until you add the four into one pipe.
Some work well without too much tweeking. Others are problematical.
Do not get bogged down with main jet substitutions and needle heights.
All problems go away when air constrictors are installed in the air bleed hole to the main jet.
Air bleed constriction reduces the amount of air available within the emulsion tube. Therefore, suction
or vacuum in the carb has a greater effect on drawing fuel from the emulsion tube because the bleed or
vent to atmosphere is reduced.
Steve Smethurst

User avatar
zed1015
Hardcore
Hardcore
Posts: 2826
Joined: 2nd Nov 2005
Location: Somewhere between Scunny and Goole.

Re: Carbs on an 1100 Unitrack engine

#8 PostAuthor: zed1015 » Thu Jan 09, 2020 5:53 pm

stephensmethurst wrote:Fitting appropriate jets is sound advice until you add the four into one pipe.
Some work well without too much tweeking. Others are problematical.
Do not get bogged down with main jet substitutions and needle heights.
All problems go away when air constrictors are installed in the air bleed hole to the main jet.
Air bleed constriction reduces the amount of air available within the emulsion tube. Therefore, suction
or vacuum in the carb has a greater effect on drawing fuel from the emulsion tube because the bleed or
vent to atmosphere is reduced.

Steve Smethurst


IF you are going to run without the airbox I can supply the air corrector jets mentioned above.

Roger Hill
100Club
100Club
Posts: 157
Joined: 1st Sep 2008
Location: Nottingham

Re: Carbs on an 1100 Unitrack engine

#9 PostAuthor: Roger Hill » Fri Jan 10, 2020 4:43 pm

Hi thanks to everyone who has replied to my original question.
I have ordered a set of main jets as per z1100 Lawson spec and will try them first.
I am using a stock air box and filter rather than pod filters.
Exhaust front section is a Delkevic stainless 4 into 1 .
I have not as yet got an end can but will be fitting something that is road legal rather than free flowing (noisy)
Steve would you still suggest fitting the air constrictor jets in the air bleed holes with a stock air box and filter ?
Still loads to do but its getting there.

Julian_Boolean
Custard Cream
Custard Cream
Posts: 740
Joined: 20th Oct 2016
Location: Ipswich

Re: Carbs on an 1100 Unitrack engine

#10 PostAuthor: Julian_Boolean » Fri Jan 10, 2020 5:01 pm

What frame is the engine going in?
An expanding collection of parts pretending to be a Z1100R and a Yamaha FZ750

Roger Hill
100Club
100Club
Posts: 157
Joined: 1st Sep 2008
Location: Nottingham

Re: Carbs on an 1100 Unitrack engine

#11 PostAuthor: Roger Hill » Fri Jan 10, 2020 7:38 pm

Its a modified gpz1100 b1 frame
Its been slimmed down slightly at the back of the top tubes and had a new set of front tank mounts fitted to take a pattern Z1 tank and the rear end has been changed to take a pattern Z1 fender B2 forks with clamps fitted to take Z1 style high bars.
The idea being a GPZ1
Its moved forward a bit more since the pictures but still had a way to go.
Attachments
IMG_0560.jpg
IMG_0563.jpg
IMG_0561.jpg
IMG_0562.jpg

User avatar
Richard L
100Club
100Club
Posts: 158
Joined: 19th Jan 2012
Location: Heidelberg, Germany

Re: Carbs on an 1100 Unitrack engine

#12 PostAuthor: Richard L » Fri Jan 10, 2020 9:04 pm

Hi Roger, Bike looks very good , my B2 has pod filters on BS 34's and a dynojet kit so have no jetting advice for you but I am curious as to whether a stock airbox will fit a B1/2 frame because the battery is much lower than on a 1000J/R and I was under the impression it would not fit without cutting bits off .The Gpz's I have seen
with an airbox have used a Unitrak 750 airbox which is a bit smaller.

Roger Hill
100Club
100Club
Posts: 157
Joined: 1st Sep 2008
Location: Nottingham

Re: Carbs on an 1100 Unitrack engine

#13 PostAuthor: Roger Hill » Fri Jan 10, 2020 9:53 pm

I have lowered the battery tray so that the battery sits further back and lower down .


Return to “Bike Help”

Who is online

Users browsing this forum: No registered users and 17 guests