Valve clearances.

[milleplod]

Just got to wondering about the effects of not checking/adjusting the clearances for ages. Any thoughts anyone?

Pete

[Justcruising]

Essentially not a time-based requirement and the service schedule has them to be checked every 20k kms, after initial 10k kms. Variation in clearances can result in uneven power balance between the cylinders and contribute to vibration, harshness and poorer performance. Significantly increased clearance should also result to greater audible valve-train noise and significantly reduced clearance could result initially in audible blow-back though the valves not seating.

[milleplod]

Thanks for the quick reply! My ST's done 29k miles now, they were last done around 13/14k miles ago. Bike runs and ticks over very smoothly, very quiet in the valve cover area....all seems good. I'm just wondering if I should leave them alone, its the only 'service' item I've not done on this year's list prior to my trip to Spain in May.

Pete

[Herb]

Thanks for the quick reply! My ST's done 29k miles now, they were last done around 13/14k miles ago. Bike runs and ticks over very smoothly, very quiet in the valve cover area....all seems good. I'm just wondering if I should leave them alone, its the only 'service' item I've not done on this year's list prior to my trip to Spain in May.

Pete

Quiet is not always a good sign. They get quieter as the clearances close.

Given that they can be checked and adjusted in an hour or less, why leave it? It's still March, just. Plenty of time.

[milleplod]

Thanks for the quick reply! My ST's done 29k miles now, they were last done around 13/14k miles ago. Bike runs and ticks over very smoothly, very quiet in the valve cover area....all seems good. I'm just wondering if I should leave them alone, its the only 'service' item I've not done on this year's list prior to my trip to Spain in May.

Pete

Quiet is not always a good sign. They get quieter as the clearances close.

Given that they can be checked and adjusted in an hour or less, why leave it? It's still March, just. Plenty of time.

Yep, me being a lazy git I think! I've already bought the feeler gauges, so I think I'll have a look at them tomorrow. Just wondering....why exactly do the clearances close on BMW tappets? The last car I had with tappets, they got bigger as the miles racked up....I think!

Pete

[Herb]

Probably not a problem with our bikes, with modern material's etc, but as the valve wears into the seat, the top of the valve stem will be closer to the tappet, hence the gap closes.

It's such a quick job, worth doing for peace of mind.

[Humbug]

I agree, its a fairly quick job, I just stick mine on the Abba stand, stick it in 6th gear, whip off the covers and turn the back wheel watching the rockers fully open. You can see them clearly or get someone to turn the wheel for you as you watch. It turns easily with all the plugs out.

[milleplod]

I've committed myself to doing them tomorrow morning!

Pete

[The Teutonic Tangerine]

I've committed myself to doing them tomorrow morning!

Pete

The best bits are:
*the fact you can do this yourself and
*you can sit on a box to do it and
*you don't have to dismantle half the engine and
*then do hard sums and
*then go and buy shims

[milleplod]

I've committed myself to doing them tomorrow morning!

Pete

The best bits are:
*the fact you can do this yourself and
*you can sit on a box to do it and
*you don't have to dismantle half the engine and
*then do hard sums and
*then go and buy shims

I've already selected the box! Last time I did tappets was, I think, on a Triumph Spitfire 1500 back in the 80s - the hardest sum was 'the rule of 9' as I recall!

Is it the twin-cam boxers that have shims? I don't think I'd attempt the job if shims were involved tbh.

Pete

[The Teutonic Tangerine]

I've committed myself to doing them tomorrow morning!

Pete

The best bits are:
*the fact you can do this yourself and
*you can sit on a box to do it and
*you don't have to dismantle half the engine and
*then do hard sums and
*then go and buy shims

I've already selected the box! Last time I did tappets was, I think, on a Triumph Spitfire 1500 back in the 80s - the hardest sum was 'the rule of 9' as I recall!

Is it the twin-cam boxers that have shims? I don't think I'd attempt the job if shims were involved tbh.

Pete

Shims -deffo on the Water cooled models - according to the Fiche its called an "adjusting plate" and comes in various thicjnesses so its a shim.

I think it was the rule of 9 - there being 8 valves on a on an old 4 cylinder engine IE when 8 is open 1 will be closed, 3 is open 5 will be closed etc.

[Herb]

The best bits are:
*the fact you can do this yourself and
*you can sit on a box to do it and
*you don't have to dismantle half the engine and
*then do hard sums and
*then go and buy shims

I've already selected the box! Last time I did tappets was, I think, on a Triumph Spitfire 1500 back in the 80s - the hardest sum was 'the rule of 9' as I recall!

Is it the twin-cam boxers that have shims? I don't think I'd attempt the job if shims were involved tbh.

Pete

Shims -deffo on the Water cooled models - according to the Fiche its called an "adjusting plate" and comes in various thicjnesses so its a shim.

I think it was the rule of 9 - there being 8 valves on a on an old 4 cylinder engine IE when 8 is open 1 will be closed, 3 is open 5 will be closed etc.

I Spotted the deliberate error! Do I get a prize?

[The Teutonic Tangerine]

I've already selected the box! Last time I did tappets was, I think, on a Triumph Spitfire 1500 back in the 80s - the hardest sum was 'the rule of 9' as I recall!

Is it the twin-cam boxers that have shims? I don't think I'd attempt the job if shims were involved tbh.

Pete

Shims -deffo on the Water cooled models - according to the Fiche its called an "adjusting plate" and comes in various thicjnesses so its a shim.

I think it was the rule of 9 - there being 8 valves on a on an old 4 cylinder engine IE when 8 is open 1 will be closed, 3 is open 5 will be closed etc.

I Spotted the deliberate error! Do I get a prize?

Nope its just that I too haven't used the rule of Nine since I got ride of a Mk4 Cortina about 27 years ago and have forgotten how to add up - regarding valve clearances I had a Citroen Xantia that I bought with 69k on the clock and sold with over 170k (miles) and I never ever touched the valve clearances. Same with a 900 Diversion 29k to 60k and never touched the valves
. If it aint broke........

[milleplod]

Job done....they didn't even need adjusting! End float on the rocker shaft was within spec at .30mm, so I left it alone - I've read that if its adjusted right down to the bottom end of the spec, .05mm, it results in smoother running, but I'm more than happy with how mine runs anyway! Mind's at rest now though. The most time-consuming bit was finding the right size Torx for the head cover bolts. Oh, and I initially tried to turn the engine over via the rear wheel in 1st....hmmmm, soooo much easier in 6th!

Pete

[Humbug]

Yes, 6th is definitely easier