Setup 1260 GPZ Unitrak

[firyembers]

Got a street fighter gpz a3 out to 1260,38 smoothbores onit,unknown cams and zx7 running gear,been quite engine piggish really,as bought goes like stink but a tank disappears as fast as oil.

Will sort it sometime..

Anybody got similar running good etc,what jets mains pilots using etc.

It's dam rich on start after choke off,(choke too rich)goes wellish till 4k ish then pinks or the other 'orrible sound when wind the throttle

lean of throttle then ok after 5k ish and really takes off,not found the end of that curve yet,roads not long enough

So I dropped pilot from 17.5 to 15 and upped mains from 125 to next(130 or 135)

(Correction std were 135 now up to 137,5 May 24)

Not done much not home or time to play,but its on the right side of better but struggling to start,likely pilot need a bit more out turns

Anyways suggestions appreciated..thanks

[Al]

Sure this wont be a popular thing to say but 38mm carbs on an 1260 is a hell of a lot of carb. Specially not helpful if you have already put work into setting it up.
If you are going for the land speed record then that is a different matter.
I cant see an easy way to solve that riddle because both parts of youre dissatisfaction have different contradictory causes.

On the subject of pinking i would recommend a DYNA 2000.
It has a much more user friendly advance curve and potential for fiddling is endless because you can write youre own advance curves into it with extra software.
The standard curve (number5) is not 'all in' 'till 5500 unlike the 'S' curve using standard advance which is 'in out in out shake it all about' but has surely arrived by about 4000;... more or less the onset of pinking whilst these big motors are still 'pumping' and yet to come on the cam.

You can also set the timing retarded and use a 'faster advance curve (number4) which helps with starting but still gets you where you need to be.
They are not massively expensive and work with standard ,grey or green coils.
Do you know what the compression ratio or pressure is?


AL

[garyd]

I'll be using 38s on my 1170.

I'm thinking I can get them to work considering the bore sizes of modern bikes..fingers crossed.

[Al]

Gary i was thinking back over the last five years to the activity surrounding Fatty's Z1R and all its trials and tribulations.
It is 1327 so a little larger than Graham's 1260 and has 36mm flatslides.
They would propell it to 140 mph in 440 yards in less than ten seconds and during those five years their size was never a serious question. They only have 140 mains in them and the accelerator pump(s) have no bearing because the throttle is pinned from the start line.
I have 34 mm carbs on the 1170 and it is never strangled to breathe. 38 mm carbs are 20% bigger than 34mm carbs not just 4mm larger in diameter.

AL

[Robw]

I have 33mm CRS on my 1170 and it goes like stink from standing start. I have been told by others that any larger will lead to problems when pulling away from a standing start, but do come into their own at higher revs
Rob

[ollie]

i agree way too much carb ,i would lean towards 34mm for a 1260 no bigger.As theres more than enough .

[Pigford]

My 1075 Z1000 runs RS36's. Goes real good with std cams & flowed head. I think its got 20 pilots & 130 mains (long time since I had to mess with it) and its 90 bhp dyno'd.

Sounds like your pilots may be too small But as mentioned low end with 38's can be a tad fussy as fuel mixing may be suffering, but I reckon it's just dialling them in right

[garyd]

Considering the GSXR1100s ran 36s...and early R1s etc were running way bigger, it must be possible to get the low speed running sorted.

Probably an afternoon on the dyno would work a treat.

[Al]

This is only the RS series applications list but its useful to see the comparison of; different capacities, engine configurations and states of tune for the differing venturi sizes.



AL

[garyd]

Interesting....they appear to recommend the RS38s for Z1000 / Z1100

[Toyboy]

Got a street fighter gpz a3 out to 1260,38 smoothbores onit,unknown cams and zx7 running gear,been quite engine piggish really,as bought goes like stink but a tank disappears as fast as oil.

Will sort it sometime..

Anybody got similar running good etc,what jets mains pilots using etc.

It's dam rich on start after choke off,(choke too rich)goes wellish till 4k ish then pinks or the other 'orrible sound when wind the throttle

lean of throttle then ok after 5k ish and really takes off,not found the end of that curve yet,roads not long enough

So I dropped pilot from 17.5 to 15 and upped mains from 125 to next(130 or 135)

Not done much not home or time to play,but its on the right side of better but struggling to start,likely pilot need a bit more out turns

Anyways suggestions appreciated..thanks

1st thing i would do is remove the carbs remove the jets blow everything through with carb cleaner and compressed air. Then set the float heights (very important) as this dictates the amount of fuel to high to rich to low to lean

[firyembers]

Hey thanks all for the info,long time to reply but did read very early on which gave me a lot of food for thought.

Which got me searching and reading.

Read Pigfords new project and his jeting settings with 38s but found it not to be 1260 bummer only a 1075..plus a bad head

Shit mine maybe not a 1260 either..only from description of the eBay buy..
But the carbs are 38s measured them heh heh..so deffo one thing correct

Although carbs been standing,(toyboy thanks) i do not leave them with fuel in,i drain the fuel and leave them dry when away.checked float heights and are cock on,did a synchying of the carbs over xmas,they were out and found shining a light from opposite side to get slide height good.
Sudco recommend a pin diameter feel to setup as vacuum setting is unpredicatbly and i found a good feel was impossible to maintain over the 3 using no 2 as the reference.

Definatly better but its am sure a fuel air supply settings to sort

Like the idea of the modded ignition advance retard makes sense with revs versus on cam stuff.
Plus unknown what cams or even if degreed in etc..
Have a nice pair of psp3x cams with adjustable from martin(thanks) to fit if i decide whats in place is up the swannee

Although i can buy a dyno 2000 to go that path,but since i have a megasquirt project on the sidelines have since found out i can with a bit of hardware and software mods can use the MS2 to fire the coils on a 4 cylinder wasted spark and program the ignition table to what ever i feel to try.

Although will eventually go 42mm dual throttle injection tbi system off the gsxr 09 suzi..

So when i have the usd forks on with GaryD 6 pots in place,the zx12 fat fuck tyre plus a nice Jason supplied DG sprocket carrier

Just sorting some extra pilots and main jets to arrive have a better play,but i suspect low compression maybe a problem as pigford found..not ready to strip yet though

Oh and yes if not guessed will stick with the 38s,the guy whoever had the idea but no idea to do a good job or setup,likely got pissed off why he sold..maybe..

As it stands it has tons of potential and am aiming for that clock to read 200 plus,even if it's eventually of a fucking cliff heh heh

And apparently not even possible off a cliff..12 seconds freefall only gets you 125 mph 2000 ft (air resistance after that) Is there a cliff that tall..

http://www.greenharbor.com/fffolder/questions.html

"So to answer the question, we believe that after falling 5,000 feet in a vacuum, you would be going close to 7,000 miles per hour. Of course, in real life, in about 12 seconds you would accelerate to close to 125 miles per hour after 2,000 feet or so, and would not go any faster thereafter because of air resistance."