Valve clearance question

[Guest]

Hi guy's after some advice

I have a 1999 Kawasaki ZX6R G3, had it for 12 months now and its time for a service

Just wondering, do you have to have valve clearances checked / adjustied or is it something you can leave and what would happed if I do leave them, willit just loose power and get noisy?

Thanks

[eastanglianbiker]

depends on the mileage they dont need doing every service and if they are getting noisy u will hear a ticking sound from top end of engine so check in service guide at what mileages they should be done at if near that time get them done

[Guinnless]

How many miles has it done? Unless it's done mega miles or is obviously noisy or running badly then I'd leave well alone. If you are really concerned then send it to a dealer but expect a big bill!

Kawasaki specify every 8000[1] miles for valve clearance checks on my ZX-7R. Adjustment requires removal of the camshafts, changing the shim and replacing. Not for the faint hearted. Dunno if there's manual adjustment on the sixer, check with Haynes manual.

[1] this is overkill for an engine that's been run on quality oil and has not been abused. IMHO.

[Ingah]

depends on the mileage they dont need doing every service and if they are getting noisy u will hear a ticking sound from top end of engine so check in service guide at what mileages they should be done at if near that time get them done

 

To expand on this, don't leave it, it'll wreck the engine if the clearances get too far out (at least get them checked). Personally i think too many people take the view that it's expensive so they won't bother. Then eventually, bang goes the engine. It's cheaper to keep it maintained, than get a new engine when it fails.

[Guinnless]

I'd be interested in how you believe the engine would "fail or go bang" ?

[Ingah]

I'd be interested in how you believe the engine would "fail or go bang" ?

 

I was under the impression way too tight valve clearances such as those that have never been touched in relatively well used engines (they usually tighten over time), would cause 2 metal components to whack into/against each other when they expand as they operate at working temperature, and this would wreck the engine. It's vague, but it makes sense in my head, and i'm sure someone with better knowledge of mechanical theory can be more precise, or point out where i'm going wrong.

[Guinnless]

Hi Ingah,

Valve clearances gradually increase over time not decrease. This is caused by wear on the working surfaces.

On the ZX6R engine mentioned above the cams sit over the valves (hence Overhead Cam) and the eccentric lobes on the cam open and close the valves by operating on a "bucket". This bucket sits open side down resting on top of the valve stem and the top part of the bucket contains shims of varying thickness to adjust the clearance to the correct value. The clearance is there to provide a smooth take up of load as the cam lobe "opening ramp" comes into contact with the bucket, only a small factor of the clearance is there for heat related expansion.

Providing the engine has been serviced with decent oil then the clearances will barely change. They certainly don't need checking every 8000 miles like the manufacturers claim but then they must assume that the rider runs on the rev limiter on a cold engine!

I'd say after 36,000-50,000 miles it might be worth considering checking and adjusting. Excessive clearance will make itself know as a light tapping noise but won't cause any damage providing it's adjusted fairly soon.

Use a quality semi-synthetic for road use and change every 3000 miles and you'll not see any significant wear on the engine. And don't nail it till it's warmed up either!

[Ingah]

Hi Ingah,

Valve clearances gradually increase over time not decrease. This is caused by wear on the working surfaces.

 

 

That flies in the face of what i've heard elsewhere, but i suppose it could be down to a different engine design, or other people being outright wrong (maybe saying 'tight' when they mean 'loose')

 

On the ZX6R engine mentioned above the cams sit over the valves (hence Overhead Cam) and the eccentric lobes on the cam open and close the valves by operating on a "bucket". This bucket sits open side down resting on top of the valve stem and the top part of the bucket contains shims of varying thickness to adjust the clearance to the correct value. The clearance is there to provide a smooth take up of load as the cam lobe "opening ramp" comes into contact with the bucket, only a small factor of the clearance is there for heat related expansion.

Providing the engine has been serviced with decent oil then the clearances will barely change. They certainly don't need checking every 8000 miles like the manufacturers claim but then they must assume that the rider runs on the rev limiter on a cold engine!

I'd say after 36,000-50,000 miles it might be worth considering checking and adjusting. Excessive clearance will make itself know as a light tapping noise but won't cause any damage providing it's adjusted fairly soon.

Assuming newish/mechanically ignorant riders notice and/or care about it!

This does tally with what i've heard elsewhere. For example someone on the CB500 forums didn't have service have service history for their CB500, and they checked the clearancese (48K on the clocks apparently - its supposed to checked every 24K - but i bet it hadn't been done), and they were apparently way out of spec.

Either way, my advice for not 'leaving' it still stands - if there's no proof it's been done, assume it hasn't!

[Guinnless]

Hi Ingah,

Valve clearances gradually increase over time not decrease. This is caused by wear on the working surfaces.

 

That flies in the face of what i've heard elsewhere, but i suppose it could be down to a different engine design, or other people being outright wrong (maybe saying 'tight' when they mean 'loose')

 

The other people are quite wrong or getting muddled up with Valve Seat Recession on old engines that are not suitable for unleaded fuel.

 

On the ZX6R engine mentioned above the cams sit over the valves (hence Overhead Cam) and the eccentric lobes on the cam open and close the valves by operating on a "bucket". This bucket sits open side down resting on top of the valve stem and the top part of the bucket contains shims of varying thickness to adjust the clearance to the correct value. The clearance is there to provide a smooth take up of load as the cam lobe "opening ramp" comes into contact with the bucket, only a small factor of the clearance is there for heat related expansion.

Providing the engine has been serviced with decent oil then the clearances will barely change. They certainly don't need checking every 8000 miles like the manufacturers claim but then they must assume that the rider runs on the rev limiter on a cold engine!

I'd say after 36,000-50,000 miles it might be worth considering checking and adjusting. Excessive clearance will make itself know as a light tapping noise but won't cause any damage providing it's adjusted fairly soon.

 

Assuming newish/mechanically ignorant riders notice and/or care about it!

This does tally with what i've heard elsewhere. For example someone on the CB500 forums didn't have service have service history for their CB500, and they checked the clearancese (48K on the clocks apparently - its supposed to checked every 24K - but i bet it hadn't been done), and they were apparently way out of spec.

Either way, my advice for not 'leaving' it still stands - if there's no proof it's been done, assume it hasn't!

 

That's fine. You need a garage you can trust though as it's an easy way to make money for nowt. I never use garages anyway so it'd just be a day's work if mine needed doing.

[Stu]

valve clearences can go either way! tight or loose!!

valve seats can burn slightly making the valve sit in further causing the clearence to go tights dont forget we are only talking fractions of a mm for valve clearences

ive had it on a bike where a couple have been tight and a couple loose

its one of the most looked over jobs on a bike even though they are easy to do remember its only a valve check and adjust if needed if no adjustment its no extra charge

if your pretty handy with a spanner and feeler gauges they are easy to check

[Revvin Kevin]

The clearances on ZX6 J/A1P models are known to close up quite quickly as the head is supposedly quite soft. I checked my A1P at 18k and at least two valves on the exhaust side were out of tolerance and several of the intakes were on the tight side but still in tolerance. I prefer to set the valves on the loose side (a little tappety) then I can hear when they have closed up. Too loose is generally better than too tight.

When they get tight, the valves will stay open damaging the valve seats, when they are very loose, the cams and buckets will be hammered causing premature wear. Some models are more prone to wear than others and require more frequent checks. A compression check can indicate valve problems and also stalling and or poor tickover could indicate valve clearance issues.

I will be rechecking the clearances at 40k miles, 22k since the last check.

If there's any doubt, get them checked for peace of mind.