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  #1  
Old 23 Feb 2008
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Valve Clearance Help Needed R100gs

Hello, this is my first post, I have been searching the hubb for a few weeks now and have found it very useful for planning my trip but I can't seem to find anything on how to check the valve clearance on my 1988 R100GS. I'd like to learn a few things before I set off, I'm a total novice at anything mechanical, tried to do it today but got fairly confused.

Which is the intake and which is the exhaust valve? Is exhaust closest to the front wheel on both sides?

Is it essential to make sure the cylinder head retaining nuts are at the correct torque before checking clearance, if so does anyone know the size of the socket needed for this as I don't seem to have it.

When I get it to TDC, is that the right point to check both valves on both cylinders, or is that right just for one cylinder.

Any help much appreciated.
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Old 23 Feb 2008
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Once you've got the valve cover off (centre nut plus the 6mm nut front & rear, hidden inside the fins on the head), you'll see two valve & spring assemblies. The one nearest the exhaust is the exhaust valve & you've guessed, the one nearest the carb is the inlet valve.

You need to rotate the engine, either by putting it in top gear & rotating the rear wheel in the usual direction of travel or by removing the cover on the front of the engine & using either a spanner or T-bar on the nut on the end of the crank. As you look at the engine from the front, the engine rotates clockwise. Remove spark plugs from both cylinders before rotating engine.

Rotate the engine, pay attention to the inet & exhaust valves being compressed alternately by their respective valve gear. You need to find TDC (top dead centre - where piston is at the tp of the bore & both valves are closed. TDC can be determined in 2 ways:

With the plug out, poke a straw or pencil down the plug hole, slowly rotate the engine, you'll feel the piston move up the bore towards the head - you're now approaching TDC - When the pistin stops moving, you've reached TDC.However, keep rotating until you see the inlet being compressed & then released - next time you reach TDC, piston is in the correct position to check the valve clearance. Try waggling the rocker arm, there should be some free play, if not, the valves are either too tight or you're 360 degrees out on crank rotation.

Alternatively, remove the black rubber cap on the left side of the engine, near the carb, shine a torch in as you rotate engine, you're looking for the "OT" mark. Rotate as above, keeping an eye on inlet valve. Once inlet valve is closed i.e. no longer compressed, the next time the OT mark is in the centre of the hole, you're okay to check the valves, checking for freeplay as described above.

Once adjusted, repeat on the other cylinder.

TBH I think you should do this under guidance, getting it wrong can wreck an engine. If going to perservere, keep roataing the engine, familiarise yourself & hopefully understand the way the inlet & exhaust valves interact with each other. Reading a book on four stroke engines could save you a lot of grief & money.
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Old 24 Feb 2008
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What steve has said is all correct.....

But


Which is the intake and which is the exhaust valve? Is exhaust closest to the front wheel on both sides? YES


When I get it to TDC, is that the right point to check both valves on both cylinders, or is that right just for one cylinder.

FIrst off I suggest you get a Haynes manual. It will be useful to you.

When I do my tappets I do it the Triumph way, as the timing relationships are the same for BMW's as the Parallel twins.

Remove both rocker covers . Keep them seaparate as they are handed.
With the bike in top gear rotate the rear wheel forwards until one valve is rocking..
At that point adjust the SAME valve -ON THE OTHER SIDE-
When done rotate the wheel some more and repeat the process until you have done all four valves.
Now rotate again and check all four valves have the correct clearance ( when the opposite valve is rocking).
No need to look for TDC or worry about which cylinder to do.
This way will ensure you set the valve clearance at the base of the cams, as with one valve rocking the point is 180 degres away.

Last edited by oldbmw; 24 Feb 2008 at 20:42. Reason: Tripewriter malfunction
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Old 26 Feb 2008
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More airhead information

Quincy,

If you haven't come across it yet, you might want to check out Robert Fleischer's site at BMW Motorcycle Repairs . I think article #40 at Setting valves in BMW airhead motorcycles has the kind of comforting detail you need when doing something for the first time. The old guy gets a little verbose in places but he is the first to admit it. That's OK with me. His rather detailed articles on everything airhead gave me the courage to replace all the seals in my 75 R60. Good info there. Go for it.
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Old 26 Feb 2008
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Thanks for everyones help. I thought of a few more questions whilst in work today, but that link has just answered them. I'm now feeling pretty confident and i'm going to go back out there on Saturday and give it a shot. I'll let you know how I get on....
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Old 12 Apr 2008
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I've done it and it went well, the exhaust clearances on both sides needed adjusting, but now they are done and the bike is running great. I couldn't be more of a novice, so if I can do this anyone can. My advice to anyone reading this in the future thinking of having a go themselves is to go slowly and think it through but to definitley give it a try.
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Old 12 Apr 2008
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Quote:
Originally Posted by Quincy View Post
I've done it and it went well, the exhaust clearances on both sides needed adjusting, but now they are done and the bike is running great. I couldn't be more of a novice, so if I can do this anyone can. My advice to anyone reading this in the future thinking of having a go themselves is to go slowly and think it through but to definitley give it a try.
You have already learned one of teh most important things, do only one thing at a time then test to make sure all is ok.
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Old 12 Apr 2008
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Smile

Quote:
Originally Posted by Quincy View Post
I've done it and it went well, the exhaust clearances on both sides needed adjusting, but now they are done and the bike is running great. I couldn't be more of a novice, so if I can do this anyone can. My advice to anyone reading this in the future thinking of having a go themselves is to go slowly and think it through but to definitley give it a try.

Here, here!

And when you get it done, you have a much better feel for the engine: as I am riding I can "see" all the bits and pieces rotating or otherwise hammering up and down: empathy with the machinery I guess.
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