Z900 A4 fuel leak any ideas please?

[Gray17]

Thanks Gray, yes cam timing fully re checked earlier in post, 1 of 1st things i thought of, even been through it step by step with Warren def as it should be checked it 3 times, turned engine over then re checked it. So im as sure as i can be.
Thanks

[warren3200gt]

Graham is the same vac cap that's blowing off or does it vary?
For a vac cap to blow off you have positive pressure in the inlet when you should only have zero or negative pressure. If it's the same cap every time then that cylinder must either have a hanging valve or a poor seated valve or pre igniting before the inlet valve is shut.
If its 2 vac caps that come off and they are on the same coil then it's likely you timing is out on that coil. When you strobed the timing did you just do 1&4? or did you strobe both 1&4 and 2&3?

[Gray17]

Hi Warren yes same one each time, left hand cylinder when viewed from rear looking forward, all others stay put, however they arnt exactly a tight fit, push on really easily, wasnt doing this before i played with timing as far as im aware. Plenty of compression blows finger off if held over plug hole and kicked over. Checked all valves and tappets when had cam cover off, none seem to be sticking. And yes checked tim8ng on 1 and 4, then did 2 and 3.
As stated got complete new assembly from Zpower going to try fitting that tomorrow and re check timing also.
Thanks

[Al]

Whilst you in there with the baseplate out you might pull the cam and see if you have one of these shim washers in there. Can jam the advance unit when they break. Cam must go back in the same way as it came out!!! Dont follow the picture its probably the wrong way and its also the later J version just to confuse the matter.

AL

[Gray17]

Morning Guys, new day and all that!, firstly stripped out and cleaned all new Denso plugs, next removed points plate, cam and advance mechanism, completely stripped and lubricated then re fitted back to bike, i note cam can go either way round, which is silly as the plate itself is keyed, why key 1 part but not both, a simple larger tab on 1 side of cam weights would ensure it will only fit 1 way. Anyway thats all back in now, fittted Zpower contact plate assembly, complete with brand new points and condensors, wiring too, set up points gap static, will time up with strobe later.
Because of the issues I'm having i decided to invest in a compression tester, which will tell me if all cylinders have good compression and also if there all equal/similar, it will also tell me if a valve is leaking, although i lapped these in well myself, all seats had been recut by engineering firm and checked by inserting valves and pouring fuel into chamber, none leaked out. Howver its prudent to re check now, especially with issue of 1 inlet cap keeps blowing off.
Item should arrive today or (post permitting) So will test that first before moving on. Be well miffed if theres an issue after full rebuild but need to know, cant ride it as is its terrible.
Then theres cam timing, yes i checked it originally, and re checked it with Warrens help, im now 99% sure its right, but theres that nagging 1% that says it may still be that, especially as so many have got it wrong before.
I also noted another post above mine with similar issues, i read he sorted it by increasing Pilot jet sizes which is another option but its all costly guesswork. I will also re torque the head down, but dont believe this will solve any bad running as no leaks from gasket, but best be checked just in case.
Will keep you all posted after the compression test

[Ultim8pc]

Morning Guys, new day and all that!, firstly stripped out and cleaned all new Denso plugs, next removed points plate, cam and advance mechanism, completely stripped and lubricated then re fitted back to bike, i note cam can go either way round, which is silly as the plate itself is keyed, why key 1 part but not both, a simple larger tab on 1 side of cam weights would ensure it will only fit 1 way. Anyway thats all back in now, fittted Zpower contact plate assembly, complete with brand new points and condensors, wiring too, set up points gap static, will time up with strobe later.
Because of the issues I'm having i decided to invest in a compression tester, which will tell me if all cylinders have good compression and also if there all equal/similar, it will also tell me if a valve is leaking, although i lapped these in well myself, all seats had been recut by engineering firm and checked by inserting valves and pouring fuel into chamber, none leaked out. Howver its prudent to re check now, especially with issue of 1 inlet cap keeps blowing off.
Item should arrive today or (post permitting) So will test that first before moving on. Be well miffed if theres an issue after full rebuild but need to know, cant ride it as is its terrible.
Then theres cam timing, yes i checked it originally, and re checked it with Warrens help, im now 99% sure its right, but theres that nagging 1% that says it may still be that, especially as so many have got it wrong before.
I also noted another post above mine with similar issues, i read he sorted it by increasing Pilot jet sizes which is another option but its all costly guesswork. I will also re torque the head down, but dont believe this will solve any bad running as no leaks from gasket, but best be checked just in case.
Will keep you all posted after the compression test

It really is a process of elimination and sometimes it can be a real effort.
But you're making good progress.

[gray]

you mentioned the rubber bung is an easy push fit. Try swopping the bungs around, and seeing which one pops out. If its still No 1 cylinder, then the problem is there, if that bung continues to pop out wherever you put it , throw it away and get a new one ( it may be so loose it's letting air by and causing issues)

[Gray17]

Hi Gray, yes it was an easy push fit, but to be fair they all are and so far no 1 is the only one to blow off, that said its long gone now somewhere on my last ride, only noticed on my return so put a temp rubber bung in place. Will see what results i get from compression tester, alas let down by post today so didnt arrive, hopefully it will tomorrow. What concerns me it never did this on my 1st outing before i updated the carb kits and plungers, then put on the set of vac gauges which went absolutely crackers, needles not just moving but full scale deflection both ways, at first i thought gauges faulty but now wondering if theres more to it, especially with bung blowing off, can def try swopping them around, see if problem moves.
Im really hoping that compression tester doesnt find anything untoward, as not sure i want to re strip the motor a 2nd time.
What sort of pressure should i be looking for on a Z900 A4, it didnt have a rebore, no scores or ridge on bores, head has been machined by eng shop, new seats and guides, new ex valves.
I know they should all be close to the same/ how close is acceptable? and spun over, all plugs out, fully charged battery throttle full open
Thanks

[gray]

the manual should tell you. 140-160 might be ball park figures. When my Zed needed a rebore the compressions were 85-120 ish. But it was BAD . I rode from my house to a friend in East Kilbride and it used £15 of petrol and £20 of oil.

[gray]

10% variability between cylinders might be OK

[Gray17]

A big thank you to everyone who commented and posted on this subject,(fuel leaking) the info given has been invaluable in resolving the initial issue of carb leaking. This turned out to be for several reasons not least my lack of Kawasaki knowledge when i originally rebuilt the carbs over a year ago. Ive since learned a lot and still learning!. I believe sticking float was the main reason, closely followed by poor quality float valves of varying sizes fitted by prev owner. But replacing the choke plungers and new carb kits have also played there part, along with the forums suggestions.
However unfortunately still having bad running issues, so to avoid confusion,( as now the poor running doesnt relate to leaking) it may be wiser to create a new post with my compression findings and go from there in the hope someone can help me resolve this?. Or should i just continue on this thread, or maybe change the heading? Thoughts?
Thanks

[warren3200gt]

Graham, take two reading per cylinder. One cold, throttle fully open, no plugs, cranks the starter until reading stops increasing.
Second same as first but with a few ml of oil squirted into the cylinder. A significant increase will show a rings/bore issue.
No significant increase but low reading shows a head gasket/valve issue.
No significant but decent reading means go looking elsewhere for the reason.
Handy to keep it all in one place as tracking back to see the history of what's been done will reduce duplicate answers.

[Ultim8pc]

Minimum spec for compression is 105PSI and no more than 15PSI difference between any two cylinders.
I've seen bikes with 100PSI on all four run nicer than one with higher figures but big variances.
As Warren has said, do hot and cold.

[Gray17]

Thanks Warren, thats fair enough maybe i should chsnge the heading to poor running rather then fuel leak?
As for readings the tester has now arrived so will take readings this afternoon, A4 manual says 100 psi is the limit and 130 psi normal, 10% diff between cylinders but says to take it hot, not sure why?, in my case difficult to do as got it all stripped off again so can spin over on starter but not actually run it. Will do as you suggest cold and with oil too and post findings.
Really hoping its not an engine issue/cracked ring etc as did struggle initially when fitting pistons into bores!
Thanks

Update :
Today tried out compression tester
All cold engine
No. 1 - 125 psi
No. 2 - 130 psi
No. 3 - 110 psi
No. 4 - 150 psi
With oil squirted down bore
No. 1 - 150 psi
No. 2 - 175 psi
No. 3 - 175 psi
No. 4 - 175 psi
So pressures def come up with oil in bores however min pressure according to manual is 100 psi so above that, but not ideal.
So to recap
Dont think any valves stuck as all shims turn ok
There was no scoring or lip in bores, may check again with boroscope.
Original Art pistons reused no blowby or part seizure marks present.
New hardened valve seats fitted, 4 new exhaust valves and guides, head skimmed, hairline fractures sorted and new timesert in plug 3
All valves seats re cut and lapped.
Whats your thoughts, possible causes or general wear at 20k?
Could this cause poor low speed running, but ok at mid to high speed symptoms?
Thanks

[gray]

the shim isn't attached to the bucket and the bucket isn't attached to the valve, they just sit on each other. So the shim being able to spin doesn't mean you can assume the valve is perfect.
No 3 compression without oil seems like an outlier - you said you struggled getting the rings into the bores - could you have cracked one?
How much oil did you use? And was it exactly the same amount in each cylinder?( too much oil will lead to falsely high compressions)