Z650 Carb jets

Hi Guys,
I just found this forum and was wondering if you could help me?


I'm in the UK and have a '79 Z650 (UK spec) Shes been running a little rough recently in so much as rough idle and surging on acceleration. Shes not missing but wants to go but seems as though shes been held back. Plugs are quite sooty.

Shes been re-bored to 700cc using a wiseco kit, individual K+N filters, Boyer digital electronic ignition and coils and a Marshall Deeptone.

Carbs have been cleaned thoroughly inc emulsion tubes.
Main jets were 127.5 !! (massive or what) put in by a so called mechanic.
Pilots are 15.
I got a dyno jet kit.
The mains supplied are 118 and 122.
New plugs and new battery.
Coils/ignition a little over 1 year old.

What size mains,
What size pilots and where to put the clip on the needles please?

The dyno instructions dont say what jets to use but indicate the clip on groove 2 with the washer above.

Thanks in advance.

The sun is shinin' and I wanna go ridin'

Post edited by: crossy2425, at: 2006/05/08 13:51

What carbs are you running???VM24S???iF They are Myself I would start with the 118 jets clips on the needles at #3 from top and keep the 15 pilot jets to start with.Wet set the floats.Bench sync the carbs and then fine sync them with a manometer.What plugs are you running?? Have you checked the mechanical advance to see if it was free or sticking?? Read the plugs and let the engine tell you what it wants.You want a nice tan color on your plugs.Alittle rich (dark) will not hurt but white or lean will.
You can find alot of info in the file base on this site if you get into a problem

Rammey thanks for the reply.

Yes they are the VM24's.

The bit a seem to have a problem with is how to actually measure the float heights.
All the manuals talk about Kawasaki tool........

Would a short length of clear tube do the job just as well?
Or can they be measured with a vernier gauge? If so would you have simple instructions step by step?

Plugs are new NGK B7es with new NGK leads and heads.

Battery was a bit suspect so i'v ordered a new one, that will be here tommorrow.
Mech advance seems fine, Cant sort that properley til shes runnin right though.

Lookin forward to your answer.
Gaz

Post edited by: crossy2425, at: 2006/05/08 14:37

Welcome Gaz.

You can use a clear piece of tube to set the float heights/fuel level. Just find a piece thats a tight fit in to the drain screw hole, and hold the other end up next to the carb. I can't remember the exact measurement off hand, but it's measured from the bowl and carb body mating surfaces.

Thanks for that Rob.

Its 8-15PM here and light is now fading, so i will take a look at the heights tommorrow. Early start 5am for work so I need to start chilling soon!!

Thanks for the tips, I'll keep you informed.
Gaz

I have a 78 KZ650C with a Wiseco 720cc kit, 4 into 1 pipe and pod filters. I also have the VM24 carbs, my jetting is.

Mains 118
Needle clip, second from bottom
Pilot jets 17.5 with the screw turned out 1 1/2 turns
This gives me prefect jetting. The bike runs great throughout the RPM range.

OK carbs sorted.
Still surging (really bad) at small throttles,any gear. When opened up she really goes but in the back ground is this surging, though barely noticeable at larger throttle openings. I will try a larger pilot jet.

HOWEVER

After being stood for a while (A few weeks) I did a compression test. Pot 1 and 2 spot on 3 and 4 ZERO.
Very surprised condsidering its been re-bored and new gasket, tried starting her and she ran on two for a few minutes then 3 and 4 came in. Been fine since???

I have noticed a very loud ticking from pot 4 and some spitting through the air filter on that pot.

Would incorrect valve clearences cause this surging/spitting?
All this came from a 10 mile test ride.

As i was coming home she cut out completley. Re-started big backfire then started again. Luckily was about 200 yards from home.

Ordered a gasket set today so the heads coming off. and will check clearences.
Coupled with the above does it sound like an exhaust valve or inlet valve problem?

Any help ideas appreciated.
Gaz

Befor getting into the carbs anyfarther or taking the head back off. make sure the valve clearances are with in spec you can do this while on the bike.Tight valve clearance will cause it to stop running after it warms up a bit.Beleive me I pulled my hair out and drank lots of beer trying to figure this out.I though it was a carb problem my self.reshimmed the valves which can be a royal PITA but take you time and the results will be rewarding.

by the way keep you valve clearances a little on the loose side of the recommendations of the manual.When the engine heats up the clearances will get tighter!!

I am running my clearances at .006 of an inch on the intake and .008 on the exhaust.
Good luck and take your time double check the measurements