03 zx12r number 4 misfiring

[nickjt]

mmmm, some more good info there. Thanks. O.K, sounds like i should get the battery tested, then I will do a valve clearance check, but i think i will do compression check first. Seems to me to make sense to check compression before doing valve clearance check.... So, if i have a "tight" valve (which is what i am leaning towards) How do i check the clearance on that valve??? is it a case of taking the shim out, and taking a "stab" at how much thinner i need to go on the new shim before i get clearance, then re-checking, and re-checking again, and again before i get clearance, or is there a more precise way of knowing exactly how tight it is??? And, lets say, Just in case i have a BURNT valve! and i need to do a valve job!!! Can the head be removed from the bike without taking the engine out??? Thanks guys.

[ironkiwi]

Yes you can take the head off without taking the engine off.
A bit of fiddling round to get the throttle bodies loose.

[Gosling1]

.... So, if i have a "tight" valve (which is what i am leaning towards) How do i check the clearance on that valve??? is it a case of taking the shim out, and taking a "stab" at how much thinner i need to go on the new shim before i get clearance, then re-checking, and re-checking again, and again before i get clearance, or is there a more precise way of knowing exactly how tight it is......

You check the clearance like normal - with feeler guages. If the clearance has closed right up, then yes you need to fit a shim a couple of sizes smaller - re-fit the cams and torque everything down - then check the clearance again. This could take a few times to get the clearance correct....

My advice would be that it is very unlikely to be a valve clearance issue, unless you have been drag-racing your 12, 5 nights a week for the last few years. The valve seats in these bikes is very hard and the clearances don't change much. My 12 has now done almost 60,000km and it has not had *one* valve clearance issue at all. Not even had the initial clearances changed - my local dealer head mechanic reckons that even with owners bringing in their 12's at 48000km for the first clearance (after the factory changed the service interval from 12k, to 24k - then doubled it to 48k !) - none of the 12's they have done actually needed the shims changed.

Valve clearance does not cause an issue with misfiring anyway - it will manifest as a starting problem that gradually gets worse and worse, as the clearances close up and you then start to lose compression because the valves are actually not sealing properly.....

......Yes you can take the head off without taking the engine off
A bit of fiddling round to get the throttle bodies loose......

Take a head off a 12 without taking the motor out ?? You mean you can take the head off if you rotate the motor downwards......because there is no way in hell you can lift a head off a barge if the motor sits in its normal position.

[ironkiwi]

.... So, if i have a "tight" valve (which is what i am leaning towards) How do i check the clearance on that valve??? is it a case of taking the shim out, and taking a "stab" at how much thinner i need to go on the new shim before i get clearance, then re-checking, and re-checking again, and again before i get clearance, or is there a more precise way of knowing exactly how tight it is......

You check the clearance like normal - with feeler guages. If the clearance has closed right up, then yes you need to fit a shim a couple of sizes smaller - re-fit the cams and torque everything down - then check the clearance again. This could take a few times to get the clearance correct....

My advice would be that it is very unlikely to be a valve clearance issue, unless you have been drag-racing your 12, 5 nights a week for the last few years. The valve seats in these bikes is very hard and the clearances don't change much. My 12 has now done almost 60,000km and it has not had *one* valve clearance issue at all. Not even had the initial clearances changed - my local dealer head mechanic reckons that even with owners bringing in their 12's at 48000km for the first clearance (after the factory changed the service interval from 12k, to 24k - then doubled it to 48k !) - none of the 12's they have done actually needed the shims changed.

Valve clearance does not cause an issue with misfiring anyway - it will manifest as a starting problem that gradually gets worse and worse, as the clearances close up and you then start to lose compression because the valves are actually not sealing properly.....

......Yes you can take the head off without taking the engine off
A bit of fiddling round to get the throttle bodies loose......

Take a head off a 12 without taking the motor out ?? You mean you can take the head off if you rotate the motor downwards......because there is no way in hell you can lift a head off a barge if the motor sits in its normal position.

Yeah thats right, been a while.
Once we saw the hole the valve stem made through the piston we put it back on again!