TOPIC:

Regarding the jet sizes for sure if I had 90 secondary mains in my carbs then I would have less gas flow and lean running but this does not happen in the Spectre and the only reason I can think of is that the Spectre carbs have different needles. I have never seen a Spectre carb needle but if you examine one you may find the number from the Haynes manual stamped on it. Also see if it is adjustable. Does it have grooves for a little clip so that it can be raised and lowered ?
To help identify your bike there is some info on frame numbers on page 6 of the Haynes. Also see the table below.

So now with the 132 jets and clean passages you cant rev over about 6k you got a good idle but still cant get over 6000 rpm.
I"m starting to run low on ideas but am thinking that holes in the diaphragms could be the cause ....if your repair has washed off. Or poorly fitting .......failing to raise the needle all the way under vacuum
Clean air filter and everything ship shape in that area ?
What colour are your spark plugs ?
Checking valve clearance would be a good idea with a new bike with no history
Battery voltage ? grasping at straws here
What exhaust have you got ? original or 4 into 1 ? I have 130 secondary main and a 4 into 1 exhaust + stock airbox and filter

Just checked my parts cd - Standard settings for 1982 KZ750 H3 should be :
Pilot Jet : #35
Primary : 62 or 65
Secondary : 90 or 125 .
Jet Needle : #N01A.
Just a thought but is that a Dynajet kit in there and standard airbox ?
JBM - Ohio.
Diaphragms if they have yours are $19.50 each plus $27 international so a set of 4 with post for $105 is pretty damn good.

Zephyrrider wrote: Just checked my parts cd - Standard settings for 1982 KZ750 H3 should be :
Pilot Jet : #35
Primary : 62 or 65
Secondary : 90 or 125 .
Jet Needle : #N01A.
Just a thought but is that a Dynajet kit in there and standard airbox ?
JBM - Ohio.
Diaphragms if they have yours are $19.50 each plus $27 international so a set of 4 with post for $105 is pretty damn good.

Thanks Zephyrrider, the jets have the Keihin stamp on them so assume its not Dynojet they look pretty old and original.
Airbox & filter are standard and exhaust is standard 4 into 2.
My Haynes manual seems to say the same, ie that all E,H and L models should have35, 62 & 125 jets for pilot main & Secondary, but it says the N1 models (which are the spectres) run 35, 65 & 90 jets. The thing is ive now checked my frame number and my bike model is actually a 1983 H4 model, so im not sure whats going on as it has the jet setting for the spectre N1's? Strange, but anyway as i mentioned earlier ive changed the jet size to a 132 and seeing as they seem to be the exact same CV34 carbs for all models im hoping this will balance it out.
Im thinking the Spectre must of had a different size airbox and exhaust back flow pressure hence the need for the much smaller secondary main jets? and that someone at somepoint has replaced the carbs on my H4 for a second hand set of CV34 carbs but perhaps accidentally picked up the spectre model ones and havent checked the jet sizes? otherwise i dont know why someone would go from 125's to 90's? unless they had an aftemarket exhaust i guess.

Thats pretty good value for the diaphragms, thanks for the lead, ill chase a few other things up like the valves etc and then invest in a new set if all else fails.

JR Wrote:

"Regarding the jet sizes for sure if I had 90 secondary mains in my carbs then I would have less gas flow and lean running but this does not happen in the Spectre and the only reason I can think of is that the Spectre carbs have different needles. I have never seen a Spectre carb needle but if you examine one you may find the number from the Haynes manual stamped on it. Also see if it is adjustable. Does it have grooves for a little clip so that it can be raised and lowered ?
To help identify your bike there is some info on frame numbers on page 6 of the Haynes. Also see the table below.

So now with the 132 jets and clean passages you cant rev over about 6k you got a good idle but still cant get over 6000 rpm.
I"m starting to run low on ideas but am thinking that holes in the diaphragms could be the cause ....if your repair has washed off. Or poorly fitting .......failing to raise the needle all the way under vacuum
Clean air filter and everything ship shape in that area ?
What colour are your spark plugs ?
Checking valve clearance would be a good idea with a new bike with no history
Battery voltage ? grasping at straws here
What exhaust have you got ? original or 4 into 1 ? I have 130 secondary main and a 4 into 1 exhaust + stock airbox and filter"

Thanks for the frame number diagram, i now know my bike is the 1983 H4 model, checked the needle its a N01A which is correct & it doesn't have the adjustable clip settings it seems, just a screw out head.

Checked the diaphragm fix and it seems to be holding well no leaks as far as i can tell, i used black flexible chemical resistant gasket maker for the job and seems to have worked a treat. As i said above though i think i will replace them if i cant figure this out, it just seems odd because everything should in theory be working well now i double checked all the channels and jets etc and they seem fine. Could the slides be sticking for some reason maybe? they seem pretty clean too though.

Airbox and filter standard and exhaust standard 4 into 2. Air filter looks clean but ill take it off and give it a wash out anyway just to eliminate another variable.

spark plugs are new, but ones i took out were not fouled they just looked blackish to normal colour.

Battery is holding decent charge and bike turns over well every time on the button.

Do you guys think bad valve clearances could cause the not revving above 6k symptoms or do you think im barking up the wrong tree there?

Cheers!

So the motor just chokes at 6000 ?
Did the black stuff on diaphragm make any diff.
There is a bit of assembly for those good priced diaphragms also - check out site mate.

Not really chokes just sort of hits an invisible wall!
I had a look on JBM, seems pretty straight forward, they look good quality too, think i will go for a set soon.

Another thing i just thought of was that i replaced the airbox boots but not the carb to inlet rubbers, they didnt seem too bad though, and i sprayed WD40 over them all whilst the bike was running so that would of shown up an airleak i assume? just wondering if there could still be a leak somewhere though?

Nice bike btw, i used to have a ZR550 in Eddie Lawson kawasaki green colours, cool looking bike, was slightly underpowered at top end though, i hear the 750's are a lot quicker, wouldnt mind another some day, i'd get 750 instead though i think!

For identifying the bike,you could try Z Power.They helped me with my CSR. Also,just a thought but Ive heard of some bike restricted with a rev limiter,could this be worth checking? Good luck,hope you get it sorted.

Yea good idea i got my Carb/airbox rubbers from them, they know their stuff. Pretty sure it hasnt got rev limiters in the inlets but i will double check, would they just be located between inlet manifold and the rubbers?
Cheers

Special KK wrote: Not really chokes just sort of hits an invisible wall!
I had a look on JBM, seems pretty straight forward, they look good quality too, think i will go for a set soon.

Another thing i just thought of was that i replaced the airbox boots but not the carb to inlet rubbers, they didnt seem too bad though, and i sprayed WD40 over them all whilst the bike was running so that would of shown up an airleak i assume? just wondering if there could still be a leak somewhere though?

Valves would be worth checking but I am unsure if out of spec clearances would be the cause.

Air leaks usually cause lean running (your plug colour is good) and tiny leak at boots often cause spit back into the carb at idle or low speed. Are your vacuum caps on carb nipples ok ?

I'm approaching the outer limits here - when you operate the throttle do the throttle flaps/butterflies go from their just off vertical rest position to fully horizontal?

I'm still thinking the needles on the end of the slides may not be rising as far as they should. Perhaps sticking? Can you poke a finger in from the back and see if they go up and down freely and if any move up down faster or smoother than others?

Did your bike being a US import come with a mess of snorkel air tubing under the tank which connects valve cover carbs and airbox ?

Davido mentioned a rev limiter but I have never heard of one on these bikes. Possible though.

I dont know much about them but from what iI heard they are electronic devices and are fitted in the rev counter or the wiring to the rev counter.I think theyre more common on Jap imports but its worth having a sniff around the wiring loom and see if theres anything suspicious hanging off it.
good luck

If not already done, would also use a strobe-type timing light to confirm that the ignition timing is correct, and also assure that the automatic timing advancer is functioning properly by watching for it to move quickly forward and backward as rpm is varied by blipping the throttle.

Sometimes a poorly maintained advancer gets rusty and corroded, and the weighted arms fail to open.

However, this probably doesn't explain the invisible wall at 6000 rpm when the engine is in neutral, because even if the advancer is frozen in idle/retarded position, the engine would likely rev beyond 6000 rpm in neutral.

Is it for certain that the engine is combusting on each and every cylinder?
(Spray water mist onto the exhaust headers a few seconds after starting cold engine, and the water should instantly sizzle and evaporate off of every header pipe.)

Good Fortune!

Great suggestions, as always from Patton

Found this recent post regarding sticky slides

www.kzrider.com/forum/3-carburetor/59629...itation-and-stalling

Good luck