Airhead valve clearances

[wolfeontwowheels]

Hi all,

I've no doubt this has been covered before but I can't find the relevant thread.

I'd appreciate any advice on how to set the valve clearances on my R100GS correctly. When I follow Clymer's instructions and set to 0.010mm and 0.020mm, it sounds like bag of spanners (I'm guessing because components have worn over the years and factory settings don't take this into account?).

I've also been advised by a mechanic that the best way is to get the engine hot and then close the clearances down to much less than factory settings. I can imagine that this second option would take into account the individual condition of my engine, and would quieten it down, but is it likely to cause damage?

Thanks in advance!

 

[England-Kev]

I set my R80ST at 10 and 15, on a stone cold engine...

 

[cookie]

Hi all,

I've no doubt this has been covered before but I can't find the relevant thread.

I'd appreciate any advice on how to set the valve clearances on my R100GS correctly. When I follow Clymer's instructions and set to 0.010mm and 0.020mm, it sounds like bag of spanners (I'm guessing because components have worn over the years and factory settings don't take this into account?).

I've also been advised by a mechanic that the best way is to get the engine hot and then close the clearances down to much less than factory settings. I can imagine that this second option would take into account the individual condition of my engine, and would quieten it down, but is it likely to cause damage?

Thanks in advance!

are you sure you adjusted the clearances at TDC compression? sounds like maybe you didn't, and set them on the wrong stroke.

 

[Cook1e]

http://www.bmwmoa.org/forum/showthread.php?t=4125

There are also articles from a guy called "Oak Oakleshen" (http://www.airheads.org) which are deemed to be the bible on all Airhead mechanical matters. Used to use these resource when I had an R80 about 100 years ago, but it all seems to have changed, unsurprisingly...

 

[The Other PaulG]

Did you have to make much adjustment?

If so, it's possible that the clearances were too tight to start with... it would have sounded nice and quiet pre-adjustment, but a clackety airhead is a far happier and healthier beast.

So... don't worry about some valve noise, that's healthy, unless it's TOO loud.

PG

 

[Captain Black]

are you sure you adjusted the clearances at TDC compression? sounds like maybe you didn't, and set them on the wrong stroke.

I get the little mark up In the viewing window, then just feel which two rockers have play In them, and thats your compression stroke on that side. You can pull them backwards and forwards and feel them tapping, they are the two to adjust, as the valves on that cylinder are closed. Then rotate the flywheel a full turn and feel them rock on the otherside and adjust that side.
No doubt someone will come along and say this Is a load of bollocks, but It seems to work ok for me.
That said I know fuck all so don't listen to me anyway.

 

[cookie]

i stick my thumb over the spark plug hole to feel for compression, then find TDC with a screwdriver (after removing thumb from hole)

anyway, if you do set them on the wrong stroke, the engine runs but rattles somewhat DAMHIK

 

[England-Kev]

I get the little mark up In the viewing window, then just feel which two rockers have play In them, and thats your compression stroke on that side. You can pull them backwards and forwards and feel them tapping, they are the two to adjust, as the valves on that cylinder are closed. Then rotate the flywheel a full turn and feel them rock on the otherside and adjust that side.
No doubt someone will come along and say this Is a load of bollocks, but It seems to work ok for me.
That said I know fuck all so don't listen to me anyway.

+1

 

[Beemerboff]

I use the mechanics method and check with the engine hot and running at a tickover - it works for almost every auto mechanic so it should work for us.
Mechanics rarely have time to work on a stone cold engine , so it it better to work on a fully hot one than something in between

You will need something to catch the oil, of course, and it is just a matter of checking that on the hot engine you can fell just the slightest amount of free play, and that all the valves feel the same.No need for gauges.

In my experience there is an added bonus in setting them this way - with all the clearances even on a hot,running ,motor it will be noticeably smoother too.

On modern OHC bikes where access to the valves is difficult the check is usually made before any dismantling with some sort off stethoscope - if they all tick around the same they don't get touched unless the owner insists and authorises the 4/6 hrs it can take to access them , remove the cams and re shim the buckets, etc..

On the airhead the noise can also be excessive end float in the rocker , and that can be checked hot too, but how it is corrected will depend on the rocker arrangement on your bike.

 

[Smug]

You are probably using a set of imperial feeler gauges.

The clearances will not be 0.010mm and 0.020mm. They will be 0.1mm and 0.2mm which is 0.004" and 0.008"

 

[wolfeontwowheels]

Many thanks for all the info guys – as I suspected, a few different schools of thought! I'm inclined to go with the mechanic's advice as per Beemerboff – the bike really does sound horrendous now I've fiddled with it.

In answer to some questions – yes I did it with the OT mark in the crankcase window, my feeler gauges are definitely metric and the bike was nice and quiet (with a little bit of rattle) before I meddled with it – only just bought it so felt the need to fettle!

Next up I aim to see how badly I can change the lubricants.

 

[cookie]

just do it as per the book. cold.

switching to a method used simply to get things done while the engine is hot and requires a degree of feel you don't have is fucking daft.

ps. i like Smug's thinking that you're mixing up metric and imperial gauges.

 

[Smug]

You are probably using a set of imperial feeler gauges.

The clearances will not be 0.010mm and 0.020mm. They will be 0.1mm and 0.2mm which is 0.004" and 0.008"

Take a look at your manual again because you did say in your original post that the clearances are 0.010mm and 0.020mm which is far too tight.

 

[Beemerboff]

With respect, the cold clearance is irrelevant - the only thing that matters is that there is clearance on a hot engine, and the cold clearance is a approximation of what might be required when the motor is running, heats up and expands, and in my experience this can vary from bike to bike, and valve to valve.

So, the simplest way to check that your cold approximation is correct is to let the motor warm up and check while it is running - you will get instant verification, and as I said before , if you get all the hot clearances equal the motor runs smoother and better too.

And I can't see anything daft in that.

The P.O. of my G/S had a specialist BMW mechanic fit a OEM 1000cc conversion, then sold the bike cheaply because the bike was as rough as a boars bum, and everyone including the mechanic told him that that was unavoidable with a 800 cc motor converted to 1000cc .

It isn't of course, and I eventually managed to get it running the smoothest of all my bikes.
One of the keys to smoothing it out was setting the valves by feel/hot - no matter how carefully they were set cold for some reason on this bike there was a big variation hot, and the first run after setting them equal/hot was a real eureka moment.

An electronic ignition which fires exactly 180 degrees apart was a great help too, FWIW.

 

[cookie]

The reason I said it was a daft idea in my previous post was that i felt the limited experience of the OP did not lend itself to a tricky process that needs a fair degree of experience and judgement, while simultaneously being showered with hot engine oil.

But just to clarify, I think it's a daft idea anyway. my experience does not suggest that a minor variation in valve clearance makes a significant difference to an airhead's running, so it's not a technique I would consider.

The obvious way is to do it as suggested by BMW, and IME the way that is used by their dealers: cold on a static engine. It's not like he hasn't got time to let the thing cool, is it?
The OP has stated that it was only noisy after he touched it. There's a clue there. It just needs setting properly.

 

[Rob Farmer]

Many thanks for all the info guys – as I suspected, a few different schools of thought! I'm inclined to go with the mechanic's advice as per Beemerboff – the bike really does sound horrendous now I've fiddled with it.

It may well not be your fiddling. Do you have any records of the valves and guides being changed? What sort of miles has the bike done? You should be changing the valves guides around the 40-50k mark.

As well as the valve guides you need to check the end float of the rocker arms.

 

[England-Kev]

I know it is different in the clymer manual, but it says .10 & .15 in the genuine BMW Workshop manual, so if the previous owner had set them at this spec, it would have sounded quieter, than setting them at .10 & .20.

This is a good reason why it is worth checking them before adjusting, maybe they were quiet because he has valve recession?