Help Please

Hobes

Active Member
Hobes is the handle and Gday to all.
I joined this forum nearly 2 years ago so that I could do the search fro all info regarding my ol girl, a Z750 E1 late 81 model. She has gone a bit os transform, I like bobbers, so she got customed.
I have a full piccie history to show ya, but at this stage I will post that later.
I am in the need of some serious help from you lot.

I have stripped down the carbies, cleaned all holes with carby cleaner and compressed air. I have used new gaskets and needle/seat valve, which I find funny, cos the ones shown out there use one with a rubber tip, this as is the old one is a steel tip. Anyways, I checked and set float heights to what seems the general concensus of 18mm ish? off the gasket set area, as per all the vids and tutorials, re assembled the carbs, set up a dummy fuel tank to see if all was well. The air hole to needle jet tube continually leaks fuel. I have been at it for 2 days now, trying every trick I have seen on the net, but no matter what I do, it still leaks mass amounts of fuel. When ever I turn of the fuel flow, it hisses and then squirts fuel out.

I had another set of eyes run over it but all is where it should be.

questions.
is 18mm ish the right height for these carbs to suit the GPZ?

should the needle and seat, stop fuel flow as the bowl reaches its height, thus stopping fuel running up the needle jet tube and out to air?

as I have blown compressed air thru all holes to clear them, have I accidently blown something out of that one hole? .

do I just give up and send them out to a carby mechanic? all the work I have done mostly myself, except welding the hardtail, so I am reluctant at getting someone else to help me, if it is an easy fix.



I am stuck here, I cant get the newly recondition motor to run with this fuel issue.

any help or question, please fire away, I will try to answer as best I can.
 

xb33bsa

Over 1,000 Posts
pull the bowls off and see if the flow will stop by very gently holding up on the floats,making the neddle contact the seat
if so, then either you have knackered the float level setting way high or the floats are getting stuck on the bowls and not moving freely once the bowls are in place
carry on :)
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
Blame it on the Kellys. As a certain old folk song used to go.

It sounds like either the float level is too high and can't shut off or the needle and seat are leaking. XB33's trcik should highlight which of those is the problem.
 

Hobes

Active Member
cheers lads, i will try that. But if anyone else has any other ideas or knowledge about this, fire away. As stated, been at this for 2 days, pulling what hair i have left out...
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
I'd start by checking the float level specs again. 18mm seems very high - but I don't have a manual here to check. How did you check the level? were the carbs at an angle with the float tang just touching the float needle and di you measure to the gasket surface (without a gasket in place)?

Then I would hook up an "auxilliary tank" and remove one float bowl at a time in a well ventilated outside area and see if that valve actually shuts off the fuel.

O R - test them dry with a Mityvac or just turn the empty dry carbs upside down and blow down a length of feed tube and listen for leaks - or use a Mityvac to apply vacuum and see if it seals with the carbs upside down.

Di you replace the flaat bowl gaskets by any chance? and are they too "wide" causing the floats to touch the gaskets and not close off properly?
 

Hobes

Active Member
Clymers book says 22.6mm, others have said 18.4.. Measurements were made, gaskets face NO gasket to the start of the round section on the floats. both sides. measurements were taken with the carbs upside down, new needles in new seats, so the spring pin is new. The pin does not move whether at an angle or upside down, i checked that several times. heights were checked by calipers set at 18.5mm, then dragged across float service, adjusted tang up or down until just touching. service manual says 22.6 giver or take 1 mm.
I have not physically seen the fuel level, with using a clear tube attached to drain point up the side of the carb body, this should be set at 4mm below gasket face, this is the only ting i haven;t done yet. will be doing this when i get some clear tubing.

Gaskets were changes, but, as i have 2 sets of carbies, i have used both new gaskets and the original gaskets.

Thanks all for the input.
 

Hobes

Active Member
after talking to some other guys, 22.4 +/- 1mm is what i should be doing. I have also procured some clear tubing. will see how it goes tonight.
 

hillsy

Over 1,000 Posts
Place the carbs upside down (in a soft jawed vice is good), take the bowls off, attach a piece of hose to the fuel inlet and blow. The float valves should all seat by gravity and you'll hear any leaks.

Also do not discount that one of your floats might be sinking, or the bowl gasket is stoping the float from rising.
 

Hobes

Active Member
ok here's where we now stand. there is a vent t between 1 and 2 and between 3 and 4, I had assumed these needed to be capped off. WRONG assumption. unplugged these and bingo, no more overflow. needle and seats work just fine. floats set at 22.4mm, but when fuel level was checked, we are sitting approx. 8mm below carb body. The clymers book says we need to be at 4mm.
I understand if it were over the level of carb body, I would have leaks, IF it stays where it is, could this cause the engine to not idle for very long? I will re adjust the floats yet again to get the fuel level correct at some stage.

Now, I have turned the pilot screws out from bottom, 2 turns, thinking that because I have no airbox nor pods on, this is correct for a good idle. the only thing I have changed is the needle jet to a 115 instead of 110, mainly cos, of pods and short baffled drag pipes.
from the research I have done, at idle, the pilot jet is what works the most, with any adjustment being made with the screw.

have tried to get it to idle, but it dies after a short time, and if I twist the throttle it dies completely and is hard to start.

would I be correct in assuming that maybe the pilot jet needs to be replaced, next size up?

I am writing to think out aloud, but any help from you guys would be great.

thanks for all the tips in getting atleast this far, atleast it started and ran for awhile...YIPPEE
 

Hobes

Active Member
google is your friend.

i have bought main jets 2 sizes up, plus 1 size up on the pilot jets,. As far as i can tell this is what most people say is a good starting point. plus, re adjust air mix screws after new jets are installed. As pointed out in the last email, i will re do the floats to try and get fuel levels as close to the mark as possible.

tis truly an adventure..
 

hillsy

Over 1,000 Posts
Just so you know - the HIGHER you have your floats, the LOWER the fuel level is.

In other words you need to lower the floats to raise the fuel level.

8mm below the bowl line is way too low and the bike will struggle to run at all.
 

teazer

Over 10,000 Posts
DTT BOTM WINNER
Normally fuel levels are supposed to be in the range of 3-5mm below the gasket surface. Too low and it runs lean. Too rich and it falls flat on its face.
 

Hobes

Active Member
thanks lads, just goes to show, clymers book says 18.6mm, a youtube vid says 22.4mm. both +/- 1mm. I set them at 22.5mm and the fuel level is that low. Clymers book says fuel level should be at 4mm below gasket face/carb body, so much contradiction. I will set fuel levels at 3 to 5mm below. I will wait till the new jets arrive, in the mean time i have other little jobs to finish off.
 

hillsy

Over 1,000 Posts
Another thing that may be confusing the issue is that the float valves have a spring in them. Most float height measurements are taken where the float valve is just touching the seat - which can be different to the measurement you will get if you have the carbs sitting fully upside down (IE: the spring in the float valve is compressed).

Also, my earlier post about float height measurements is with the carbs upside down (in case there is any confusion).
 

Hobes

Active Member
Hillsy, thanks man, all good. understood
its good to get some input from guys who know something. I am not one for spoon feeding. I DO research and at least have a go so that i know what is going on.

I belong to a few forums, there is always a few blokes who get on, ask the most basic questions without at least doing a google search first. IT is just forum etiquette.
 

Hobes

Active Member
re set the floats heights, to 20.5mm, checked the fuel levels, looks good enough for me.
 

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