zxr400 wont rev up. (very strange)

[steveh]

Ill try to describe this as best as i can.

The bike starts , but only seems to run on choke, when you try gas it, you either get nothing, or it bogs down.
Then, Suddenly, the revs will pick up, run fine, tick over, run right through the rev range with not probs atall,
It will then bog down and not do it again, it seems to be very intermittent.

Now, it seems to have abit of white smoke and i noticed theres abit of white stuff round the fillercap on the engine (suspected headgasket) so i dumped the oil out and it was fine, no water contamination, so i presume its just condensation?

Now, it had this problem, and when i blew down the crank case breather (not running) i noticed it blew air out of one of the case bolts in the clutch cover, as soon as i put the bolt in, it ran fine, but of course soon died.

another time i removed the crank case breather from the airbox, it ran fine, so im suspecting its some kind of breathing problem.

Ive cleaned carbs, changed fuel pumps, cdi, carbs, fuel pump relays ect.

Im using a probike test tank (not tried it yet with fuel tank)
Tried it with air box off completley, and built up, it makes no difference.

Sorry if im confusing, i am well, confused myself.
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Current : 06 Zx10r, 07 Wr450f SM, 74 850 norton commando, 63 bsa b40, 1962 Triton 650, 67 Triumph Tr6r, 1955 Triton 750, 1978 TY250E.

[NiteMare]

does your standard tank have a vacuum operated fuel tap ??

if so have you blocked off the vacuum point on the cab or inlet stub ??

that probably won't fully solve your problem but it will help if i'm correct

bogging down is often/usually due to running too lean a mixture, often caused by airleaks or blocked jets (is the filter in the airbox ?? )
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it ain't broke...

i ain't fixed it enough

[Fisty]

Had a similar (but not quite as bad) problem on my ZXR. After a rebuild i had split one of the carb rubbers and it was sucking in air at high rpm.

Not sure if your problem is the same but give it a look.
____________________
Quietly and consistently taking the piss.
TL1000R | Hayabusa | ZXR400 | TL1000S | Bandit 400 V
Fatter and faster than Fret

[MaybeGuy]

a blown head gasket doesnt always contaminate the oil y'know
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[steveh]

done a compression check, the book says 99-156 psi

Im getting like 99 on the two middle, and just touching 100 on the outers (1,4)
Wich to me sounds about low, i was expecting around 130 tbh.

any ideas?
____________________
Current : 06 Zx10r, 07 Wr450f SM, 74 850 norton commando, 63 bsa b40, 1962 Triton 650, 67 Triumph Tr6r, 1955 Triton 750, 1978 TY250E.

[NiteMare]

when you did your comp' test did you hold the throttle wide open ??

if not that'll give you a low reading....

if you still have that problem you may have either worn ring/bores/sticky rings or very tight valves ...

to give you a basic elimination (rings or valves) squirt a couple of shots of oil down the plug holes to help seal the bores then spin it over again ...

this should tell you if the valves are too tight if the readings stay low, if they raise (significantly) then the bores/rings aren't sealing properly...

always do a comp' test with the throttle wide open !!

hope that's explained the process clear enough
____________________
it ain't broke...

i ain't fixed it enough

[steveh]

aye, belive it or not im a mechanic lol.

yeah, had throttle open.

It seems there is water in the exhaust so i think that pretty much sums it up.


Well, im off to take it to pieces, ill let you know how i get on.


Steve.
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Current : 06 Zx10r, 07 Wr450f SM, 74 850 norton commando, 63 bsa b40, 1962 Triton 650, 67 Triumph Tr6r, 1955 Triton 750, 1978 TY250E.

[MaybeGuy]

all the more reason not to trust mechanics...

they seek advice from BCF.
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Blue_SV650S wrote: it was a sh1te wheelie, but it proves that he can get it up in 3rd and can do angles. In summery, mattsprattuk is a gobby little sh1tebag, dopehead tw4t, but sadly for all of us, he probably isn't THAT full of sh1te!!
Kickstart wrote: Hi I tend to agree with Matt. All the best Keith

[steveh]

[NiteMare]

[MaybeGuy]

[Noxious89123]

[NiteMare]

well it looked like you were trying to take a dig at mechanics in general so i figured it was a fair response...

i'm not a "trained" mechanic but i've worked on and built absolutely loads of vehicles from mopeds to aircooled V8 diesel tractors ...

on saying that i still struggle with some motor things and have to ask for advice or clues on forums at times, if you've been tinkering with as many varied motors as me you would realise that not all things mechanical (faultwise) are immediately obvious ...

some mechanics are specialists and know "usually" where to look because they know the quirks but they are generally one make mechanics, throw a different make at them and they can get stumped just the same as anyone else...

this guy "could" be conversant with cars rather than bikes
____________________
it ain't broke...

i ain't fixed it enough

[nick606]

[TUG]

There is just some times in life with anything where you are just totally stumped an need a bit of help, mechanics is something like that alot of the time believe it or not unless your like my tutor who has been in the game for over 40-50 years, and he asked for help for a SR50 thats fuel injected last year.
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Haz ER-5, innit!

[Noxious89123]

[steveh]

Just thought id update, and as i thought its head gasket, Very faint but you can see were coolant/oil has been getting in.

Tbh, looks like a shit tin gasket and doesnt corrispond with oil gallerys and coolent ports very well, so some ones been tinkering.

Head isnt warped from what i can tell, bit of plate glass and valve grinding compound didnt show any highspots, so im gona leave it at that and try new (decent) gaskets.

The reason i asked for advice on here, is ive never worked on a zxr400, and i know these things have there traits, it was more of a question of, "is this a common fault" as i know they eat cam chains ect.


thanks for the positive replys, Steve.
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Current : 06 Zx10r, 07 Wr450f SM, 74 850 norton commando, 63 bsa b40, 1962 Triton 650, 67 Triumph Tr6r, 1955 Triton 750, 1978 TY250E.

[Fisty]

Im afraid on the earlier ZXR400's headgaskets were prone to failing (allthough mine didnt in 70,000) miles.I think after L3/4 they changed the headgasket for a better type. Buy a genuine kawasaki part, they are £30ish and are much better than the origional old ones.
____________________
Quietly and consistently taking the piss.
TL1000R | Hayabusa | ZXR400 | TL1000S | Bandit 400 V
Fatter and faster than Fret