GPZ900R valve clearances

[gpz 89]

I have a gpz9 90 model it idles great after replacing the plugs but it coughs when I rev it a few times and starts to blow smoke
Can help please

[TONY-J]

what colour is the smoke, how much smoke, when was the bike last ridden regularly or running properly, when was oil changed, has the petrol tap been left on, is the oil at the right level, have the carbys been cleaned, i could go on and on as it could be 100s of things.....need more info

[TONY-J]

the smoke could be as simple as the petrol tap has been left on and carbys overflowed into the motor and now there could be petrol in the oil, sounds silly but my brother left his tap on, on his gpz1100 and let the bike to sit for a month and was then wondering why his fully rebuilt motor was blowing a bucket load of white smoke.

so changed the oil straight away and then realised it was like water and was alot more than he had put in ( filled a 5L container and then overflowed onto the floor ), he the realised where all his petrol had gone aswell.

filled it with fresh oil, ran it for a bit then dumped it and refilled with fresh oil again and its fine, no more smoke.

like i said seems far fetched and prob isn't your problem ( although it could be along with gumed up carbs ) but its easy to over look simple things and with no info on the bike its very hard to come up with anything other than a stab in the dark.

[gpz 89]

Hi Replaced the plugs cleaned the carbs but it still is running on 3 not 4 checked the coilsthey are ok checked the plugs 3 were good number 2 plug was wet.When I clean the carbs the pilot was set on all carbs at 4.5 turns out the book says 1.5 turns out.need some help please

[Gosling1]

my guess is valve-stem seals are shot, the smoke will be bluish-white.

You need to take the head off to replace these.

[gpz 89]

Hi Gos
After replacing the plugs the smoke stopped but the bike still runs on three

[Gosling1]

mmm - check the plug caps and leads. if they are original they will be old and crusty - new caps always helps.

It would also be worth chucking half a bottle of Wynns injector cleaner into the tank to help dissolve any old fuel deposits in the carbies. You may just have a blocked low-speed circuit. Have you tried giving the bike a big rev to see if it can 'clear its throat' ?

[Hoges]

Make sure you've got spark at #2, pull the cap and insert another spark plug and hold against the engine metal surface and wind it over for a few short bursts on the starter button.
If no spark present:-As Gos says, check the plug caps and leads. Have you got a spark on #3 cylinder?(do the same process as you did on #2),as they both share the same ignition circuit/coil/pick ups.
If spark is present on both #2 and #3 the ignition circuit would appear to be working okay then. Maybe check the coil resistance compared to the other coil(CYL1 and 4). A manual will have the resistance values.
Is the plug gapped correctly? 0.8mm is the norm.
Pilot screw setting is normally 2.5 turns out, which is the start point.

See how you go by doing above.