re: old thread: kz 750 ltd h2 1981 - jets probs

Hi kzrs

Greetings from the uk. Sorry for delay. I`ve been away working.

My bike starts, stops but cuts out.
This is the final problem. I had some great advice about cleaning the carbs.
The bikes carbs were cleaned out methodically and reassembled.
The carbs are sqeaky clean. All jets have been cleaned with a fine wires carb tool.
I discovered that my keihin carbs have A70 main jets?
The kaw manual advises A62?

Is this the detrimental to the running of the bike please?

Riders talk of rejetting,is this recommended riders?

Many thanks buddies!

Angel

Hi Angel, Good to here your still active here.
The larger Main jet would effect only above 3/4 throttle to full, and make it richer on fuel. Which could be fine where you are, with your altitude etc.
Describe in further detail the "Cutting Out". Is it at a certain RPM, or throttle opening? Or at Idle, under acceleration? The better the description the better some help will be.

hi motorhead (guru!)

thanks for your reply, great to hear from
you buddy!
i wish i'd your and pattons knowledge!

history (since i lasted posted)

the original gas tank was rusty internally.
i use used the por-15 lining kit back in 2009.
assumed that the product was gas proof.
the por-15 failed with english gas, which has
a much higher % of ethonol. the gas actually
melted the por-15 lining and created liquid residue
to enter the carbs. the lining has been removed now.
the tank is now degreased/ rust proof and
lined with a New Product!.... Sureseal. an
industrial two pack process which takes 4-6 days to
cure. it's white in color and only available in the
uk. us and canadian fuel has a lower % of ethonol
in your gas, por-15 fails here. Sureseal is far
superior motorhead!

back to erics journey to the garage.
this garage was recommended to me.
the chief mechanic, liked my bike.
advised to diagnose 'cutting out' would
take 3 days max. i phoned him after 3 days,
'not started the work yet!' he took over 16 days
and i dropped in to see how the investigation
was going. my treasured bike was outside,
dirty, scratched and looked terrible.
the guy showed me his invoice, £179 brit pounds.
advised 'stripped carb, adjusted timing, balanced
carbs. asked me to test ride it. after 7 miles
the bike cut out and was hard to start.
i complained to the garage, not happy with
16 day wait, work wasn't done. he was attempting
to con me. he showed me a 4mm piece of
tank liner, said he found it in the carbs?
i advised him 'my tank has an internal and secondary
inline filter of 4 microns, how could this piece of material
get through filtration? still not paid him.
he hasn't phoned.

Tank Restore (again)
the tank has been cleaned out and relined
with 2 pack sureseal, using a small led,
the newly lined tanks looks factory lined.

Carbs Jets Clean
removed carb, for internal checking
since por-15 tank liner failure.
i removed/checked all jet holes.
i can't find a supplier of jet cleaning
wires anywhere in the uk?
i found some fine nylon fibre optics strands
from an old garden light and this was ok
for running through some of the holes.

pardon my ignorance of the fine tolerances
of jet holes. why do they make them so small?
the plastic plug/pilot screw jet hole is minute
and easily clogged. i estimate my pilot
holes a few thou only. one particle gets
in and the carbs don't work. the failed por-15
tank liner was pickled through the english
high % ethonol gas. created many problems
in my tank/carb. the liquid residue got through?

the tank/carb is now serviced and reassembled.
just waiting for the new sureseal liner to cure.
should be ok for friday's new test ride.

Learning Curve
Like you advised in the past motorhead.
Read the kaw manual, do most jobs yourself.
i originally thought the carb restore was too complex
for me. i was wrong and having read the chapter
serviced it, with care and precision.

i will let you know about the test ride motorhead.

many thanks

angel
x



then

i mrthodicalky



in august
eric kept cutting out after hard riding.
he started fine and then cut out at traffic lights.
wouldn't start again? arranged a transporter
pickup.

the ol

steelhorseangel wrote: ...kept cutting out after hard riding.
he started fine and then cut out at traffic lights.
wouldn't start again?....

One possible cause for these symptoms could be insufficient valve clearances.

A too tight valve may fully seal when the engine is cold (during a typical compression test), but the valve seals imperfectly at normal engine operating temperature, which causes loss of compression.
The cooler engine may start easily and seem to run fine, until it refuses to idle, which is where the now hot slightly leaking valve becomes more readily apparent (at low rpm).

Valve clearances are relatively easy to "check."
It's the actual "adjusting" that gets more complicated.

Haven't reviewed the earlier threads, so may be missing where this possibility has already been covered.

Good Fortune!

Sounds like Patton has nailed it again. If it starts and runs fine until hot, then the valve clearance is probably to tight.
I can't remember if you checked/ set them or not? Best to recheck before going further, if the symptoms are such.
Otherwise, if it stalls out when running hard. It may be that you are running out of fuel. Flow may be hindered by the In-line filter/s, as some are for a pressure system not gravity feed. Also the fuel tank vent, inside the cap could be partially blocked? just a guess. Flow can be checked by removing the line from the downstream side of the filter/s, and placing a length of hose down into a can/ container. Turn the Petcock to "Prime" and check the flow, then check it direct from the petcock with no filter/s and compare. You don't want restriction.

Hi Patton

Thank for your reply!

The bike has only done 6,800 miles from 81 new!
All paperwork came from Missouri, validated the very low miles.

The vacuum petcock was replaced with a pingel gravity tap.
On, off, reserve.

The main primary jet is #70, the us kaw workshop manual advises #62.

When i cleaned the carb jets, i couldn't find the air jet,
Pilot #110
Primary main #130
Secondary main #60

A carburetor specialist told me they're a sealed unit?
How do you clean these air jets?
I can't find them?

Thanks for your advice y'all!

Regards

Angel

Hi motorhead

Thank you for your reply.

Could the carb still be blocked somewhere?
The por-15 tank sealer got eaten by the british gas.
The hot sealer residue could've lodged somewhere in the carbs.
I could clean some jets, but not all.
See my previous posting about the hidden cv34 air screw.

I upgraded the stock vacuum petcock to a mdern pingel gas tap:-

On, off, reserve, the gas flows great.

The new tank has just been re sealed with sureseal, fantastic product this.
100% ethonol proof, do a search on google, uk only.
Just a phone call/email away.

The restored tanks liner will be cured this friday.
Test ride day.

Why would mr kawasaki advise the primary main jet is #62, mine has 4 x #70?

Many thanks for your help and advice motorhead!

Regards

Angel

Even though you got a low mile motor with 6800 miles, it was supposed to have the valve clearances checked twice in that mileage. Every 3000miles. So If you haven't done so, please do so Angel.
Yes the Por could well be in the carbs still, as it gets dissolved and flows around. The Hidden Air Screws? That would be under a small metal plug that needs removing, surely they have been removed by now? Between that fellow you had do some carb work and yourself? Its #28 in the drawing. If not a small hole drilled, then a sheet metal screw screwed into the hole, and a pair of plies to pull them. You don't drill very far, as you will go through and then hit the Idle adjustment screw. These are the Idle Mixture Adjustments. The Air Jets that Patton refers to are not shown in the drawing, or probably the service manual. :blink: But they are at the Intake End of the Carb, what is the Air-Horn or Bell Mouth. They are pressed in, and should be clear when compressed air is blown through. One will feed the low speed circuit the other the High speed circuit. They work together with the fuel jets for those circuits.
I hope this helps you out some.

steelhorseangel wrote: ...bike has only done 6,800 miles....

6,800 miles is 10,943.54 kilometers.

According to the Routine Maintenance Schedule in the H1 manual (likely also applicable to the H2), valve clearances should have been checked three times by now to confirm being within specs.




Specified clearance per FSM is 0.08 mm ~ 0.18 mm for each of the eight valves.

While the clearances may be just fine, would check to confirm and rule out as possible cause for warm engine's failure to run at idle rpm.

If needed, here's an H1 manual (free download).
Click > kz.bike-night.com/media/GPz750-full.pdf

The manual is found at > kz.bike-night.com/
which site also has further good info about the KZ750 fours.

Good Fortune!

steelhorseangel wrote: Hi motorhead

Thank you for your reply.

Could the carb still be blocked somewhere?

The next time you have the carbs off you may want to check he transition holes. I had a lot of carb (same carbs as yours) problems when I got my bike first with the bike spluttering and coughing at 3,000rpmand wanting to cut out. I cleane the carbs 3 times before I found these holes. Patton has a nice diagram. The attached photo shows where to find these tiny holes. In the photo I am holding thecarbs upside down and have the throttle flap open. you wont see it in the photo but there are 3 tiny holes juts at the point where the top of the flap meets the carb body when the throttle is closed. To clean I used a fine wire with the tip bent at 90 degreesand did some very gentle poking. These tiny holes clog easily. Having said that I think Pattons suggestion is best.
Good luck

steelhorseangel wrote: Hi motorhead

Thank you for your reply.

Could the carb still be blocked somewhere?

The next time you have the carbs off you may want to check he transition holes. I had a lot of carb (same carbs as yours) problems when I got my bike first with the bike spluttering and coughing at 3,000rpm and wanting to cut out. I cleaned the carbs 3 times before I found these holes. Patton has a nice diagram. The attached photo shows where to find these tiny holes. In the photo I am holding the carbs upside down and have the throttle flap open. you wont see it in the photo but there are 3 tiny holes just at the point where the top of the flap meets the carb body when the throttle is closed. To clean I used a fine wire with the tip bent at 90 degrees and did some very gentle poking. These tiny holes clog easily. Having said that I think Pattons suggestion is best.
Good luck