kz750 ltd h2 1981 - will crank wont start fully?

The bike looks great Angel,
I thought you were having problems do to the Leak at the slide tops.
To fast of an Idle:
To much Advance on the Ignition timing, you want the 1/4 "F" mark to line up at Idle.
Vacuum leaks between Engine and Carb, Vacuum nipples, leak at hoses or carb intake boots.
Throttle not fully closing due to mechanical issue, like throttle cable slack insufficient or butterflies open from Idle screw holding them open.

Looking at your Photo's I see on the #1 carb, an open vacuum port. Is this open or do you have it hooked up? To the petcock, or the Tee to the #4 cyl, and then to the Vacuum switch up under the tank. Thats the fresh air system from the USA anyways. If not hooked to the vacuum on the petcock you can just plug/ cap it off. All of your carbs will have this vacuum nipple and need to be connected properly or plugged. If setting the vacuum sync then this vacuum nipple would be used for the Manometer vacuum sync tool.

Here are links to Keihin carb info in KZr's FILEBASE.

www.kzrider.com/filebase/doc_download/47...-shop-manual-via-omr

www.kzrider.com/filebase/doc_download/474-keihin-cvk40-via-omr

As to the clear tube test -- it measures the important fuel level in the bowls.

The float height should be adjusted to whatever is required to achieve the correct fuel level. The specified dry measured float height while upside down on the work bench might or might not result in getting pretty close to the correct fuel level.

I believe -- but not positive -- that the carbs at hand have a drain screw that serves two purposes.
(1) When tightened normally, it allows the bowl overflows to function. (2) When loosened, say 1 or 2 turns, it allows the float bowl to completely drain through the nipples from bottom of bowl.

It's the "drain" function that's used incident to the clear tube test, which measures fuel level inside the bowl during normal operation as determined by the float valve. And not the "overflow" level (screw tightened in normal position) which is much higher and supposed to prevent fuel from rising way up into the carb.



Good Fortune!

Nice pics, you're very close.

Like Patton has posted - this fuel height test cannot be ignored. Even with the floats set perfectly to the same height, there can be differences in the fuel levels. It is most important to have the fuel heights as close to same as possible, within spec.

Motorheads pretty much covered the high idle thing - maybe check to make sure choke circuit isnt sticking open.

Dont worry about the supposed correct turns out on the mix screws. they are to be adjusted occasionally anyways for environmental and altitude variables. Start anywhere you like from 1-2 turns out. A well tuned bike will start and idle in that range just fine.

Good luck.

hi gurus!....

i've decided to ditch the mechanic that i used last week. he's not contacted me again?

today i've had a good look at all of your postings and my own observations.

the mechanic of '30 years' advised me that my throttle had a little play in it.
he adjusted and he actually said 'that's ok now!'. before he touched it, it open and closed the butterflies and had about 5-8mm play. however i carefully took the carbs out the the right side today and on twisting the throttle, it didn't open the butterflies, they were stuck in a fixed
position. was this a tired mechanic or creative mechanicing! to make more money?
this is one of my first running problems, the engine wouldn't idle?
the mechanic blamed the carbs, these were an expensive serviced item, some £300 quid.

on checking the carbs, as best i could, with some knowledge! i put my carbs on to dust free
clean paper on my bench. i then took each lower nipple bowl cover off and looked at how
the floats compared to each other. again the mechanic had made two float pairs, higher
than the other two. surely they must me the same level. i've taken a photo of the carbs
without the bases on. i've now taken the higher floats off and made a TINY ADJUSTMENT to
the tang to make all the float heights the same. i've to do the clear tube method
tomorrow.

q) i don't know how to do this procedure. engine on or off?
please can you advise me in logical steps please. if the fuel levels are wrong.
i've to take the carbs out, time and time again to adjust the float/fuel levels?
is this correct?

many thanks for your help everyone!

regards

Angel





other problems found:-

NIPPLE BOWLS
on draining the nipple bowls (for carb inspection) by using clear drain tubes, connected to the nipples. i unscrewed each screw in turn. i expected the fuel to come out of the nipples, yet in
two cases the fuel came out of the screw holes? two were like this, no nipples drainage!.

PETCOCK

i think that my petcock is missing something. i checked in the oem workshop manual
and i can't find an answer to my question.

q) how many tubes should there be in the petcock tank fuel filter please?
mine has a central one, that goes halfway up the filter. it fits into a recess/hole in the petcock.
yet my petcock has room for another pipe, by the side of the main petcock tube.

Hey Angel. Way to ditch that mechanic! :lol: You're on the right track now!

As you can see, Pattons previous post clearly illustrates the procedure for checking the fuel levels. The float positions can be misleading to actual fuel levels.

This is much easier to do on a bench with some rigging/jig setup to hold carbs in place to make adjustment much easier. Not required to be on a running bike by any means.

You can make a jig REAL easy:

Make a "cross" from some 1x4 wood. Make the horizontal piece as wide as your carbs set, and make the vertical piece any height your comfortable with putting in a vice/screwing to your bench.

Remove the two far end screws that go into the carb bodies from the metal rail-(that hold the 4 carbs together) on the airbox/big opening side of the carbs.

Drill two holes thru your horizontal board to line up with the screw holes on the carb rack (removed screws), and with matching thread longer screws, just screw the whole carb rack to the horizontal board.

Place the board in a vice, and use a level to adjust horizontal pitch.

A small fuel tank from a mower/generator/power washer with a shutoff, works great, and just has to be hung/placed somewhere above the carbs.

makes life SOOO much easier!

Hope this helps!

steelhorseangel wrote: q) how many tubes should there be in the petcock tank fuel filter please?
mine has a central one, that goes halfway up the filter. it fits into a recess/hole in the petcock.
yet my petcock has room for another pipe, by the side of the main petcock tube.

If you mean there are two nipples coming off the petcock...

The large diameter one is for fuel. The small diameter one is for vacuum (from engine intake boot, or carb vacuum nipple)

Pri=Prime - ON, flows fuel freely
On=OFF - untill vacuum present, then ON.
Res=OFF - Until vacuum present, then ON (with access to lower portion of tank/reserve fuel)

Good luck.

steelhorseangel wrote: ...took each lower nipple bowl cover off and...made a TINY ADJUSTMENT to the tang to make all the float heights the same. i've to do the clear tube method tomorrow.

q) i don't know how to do this procedure. engine on or off?
please can you advise me in logical steps please. if the fuel levels are wrong.
i've to take the carbs out, time and time again to adjust the float/fuel levels?
is this correct?....

Bike engine OFF.

Clear tube test may be performed with carbs in normal position on the bike with bike on center stand or bike held in upright position.
But while the carbs remain in their normal position on the bike, it's very difficult to remove the float bowls and make tang adjustments and then re-attach the float bowls. Next, repeat the clear tube test -- and likely repeat the entire tang adjustment procedure several times before getting the fuel level exactly correct. :pinch:

Or clear tube test may be performed with carbs assembled on the workbench. Where the bowls may be removed as necessary to adjust the float tangs whereby the fuel level is changed.

It's pretty much a waste of time to goof around with measuring the upside-down float heights in hopes that such measuring and adjusting of float heights will supposedly result in the Holy Grail correct fuel level after the carbs are fully assembled.

Imo, it's better to perform the clear tube testing and float tang adjusting with the carbs on the work bench. Remembering to hold the carbs level during the clear tube testing phase.

Tip -- Save time during repetitive removal and attachment of carb bowls by using only one of the four bowl screws. There will be little if any leakage during the clear tube test, and any slight leakage past the bowl gasket won't invalidate the test.

When finished achieving correct fuel levels in the carbs, remember to install all the float bowl screws before re-attaching the carbs to the bike engine.

Bottom Line -- The ultimate objective is to achieve the correct fuel level, regardless of what float height happens to exist when the float tang is properly adjusted.

Stated another way, the correct float height (as set by the tang) is whatever height results in the correct fuel level.

Good Fortune! [/quote]

hi tek

sorry i've confused you!

when i say the petcock, i didn't mean the
fuel or vacuum connectors. it's the internal
tank filter, connected to the petcock.
inside the tank filter, there is a tube inside the filter.
this central tube fits in the base of petcock. this
is one tube, next to this tube is another hole.
does a second tube (smaller) fit into this
second hole?

many thanks

Angel

hi tek!

thank you for your advice!

i understand what you mean about the rig.
are the carbs the correct way up or upside down please?

so the carbs are bolted to the cross, fuel
fed by a temp fuel tank. then i get lost.
i've never done this before, sorry dudey!

the carbs are the correct way up or upside
down?

many thanks tek!

regards

Angel

"how many tubes should there be in the petcock tank fuel filter please?
mine has a central one, that goes halfway up the filter. it fits into a recess/hole in the petcock.
yet my petcock has room for another pipe, by the side of the main petcock tube."

Normally the petcock has 2 openings inside the fuel tank. One has a tube sticking up from it; maybe an inch or so long. The other has no tube. The one with the tube is the orifice that normally feeds fuel to the carbs. The idea is that when fuel in the tank runs low it will drop below the level of the top of the tube and the bike will appear to run out of gas. At that point, when you switch the petcock handle to "Reserve", fuel is fed to the carbs through the second orifice (the one with no tube). The opening to this orifice is nearly level with the bottom of the fuel tank (because it has no tube). So that 1 inch tube represents the level of fuel that is left in the tank when you switch to reserve. Ed

hi patton

re: setting correct fuel levels

many thanks for the clear tube method.
i'm slightly confused about setting up the
rig!...

1) make a wood cross shaped frame
to hold the set of carbs. are the carbs put
upside down, with the nipple bowls on the top?
connect up overflow/drain tubes to nipples.

2) connect up a temp fuel tank to feed carbs.

3) unscrew each bowl in turn, turn screw to
fill each overflow tube to prove fuel level?
adjust float levels as and if necessary?
repeat 2,3, 4 nipple bowls.

is my understanding correct?

please read my posting with a photo today.

many thanks

Angel

what stars you all are.

many thanks!... i only put one tube in the centre,
the same length as the workshop manual.
the manual assume common knowledge.

i would love to see a photo of how
to set up a wooden cross rig, to
bolt on your carbs, which way though?
correct way up or upside down?

all nipple bowls off one at a time or all together?

i'm confused about the correct way to
set the above rig up? ..... damsel in distress guru's!