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Valve clearances

Submitted by mark_woodward on Thu, 09/02/2012
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Commando

Hi Chaps - to set the valve clearances on my BSA Rocket 3 avoiding feeler gauges (they're an awkward fit in the rocker-box 'area') I work on the basis that the adjusters are 24 TPI thus I just screw in the adjusters such that they just touch the valve stems and then back-off a certain amount (circa 1/4 turn) to give the correct clearance - works every time and allows for any wear in the valve mechanism. I'd like to use the same method on my MK2A Commando - can any of you advise as to the thread pitch on the adjusters ? - I cannot find this info anywhere - it may even be the same as the BSA.

Thanks

Submitted by colin_sharpe on Thu, 09/02/2012

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The locking nuts fit a 1/4" British Standard spanner, so I strongly believe the threads to be 1/4-26, either BSF or CEI (Both have the same pitch). Mind you, a couple of quid spent on a set of feeler gauges might not be a bad investment!

Submitted by mark_woodward on Thu, 09/02/2012

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Previously wrote:

The locking nuts fit a 1/4" British Standard spanner, so I strongly believe the threads to be 1/4-26, either BSF or CEI (Both have the same pitch). Mind you, a couple of quid spent on a set of feeler gauges might not be a bad investment!

Thanks Colin - I do have plenty of feeler gauges but I prefer the method I described - -

Cheers,

Submitted by david_lord on Thu, 09/02/2012

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Previously wrote:

Hi Chaps - to set the valve clearances on my BSA Rocket 3 avoiding feeler gauges (they're an awkward fit in the rocker-box 'area') I work on the basis that the adjusters are 24 TPI thus I just screw in the adjusters such that they just touch the valve stems and then back-off a certain amount (circa 1/4 turn) to give the correct clearance - works every time and allows for any wear in the valve mechanism. I'd like to use the same method on my MK2A Commando - can any of you advise as to the thread pitch on the adjusters ? - I cannot find this info anywhere - it may even be the same as the BSA.

Thanks

Hi Mark

I think you'll find they are 26tpi. The method you describe is a lot less fiddly than using feeler gauges and it allows for any indent in the top of the valve stem.

David

Submitted by mark_woodward on Sat, 11/02/2012

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Thanks for your help - I have found the info and as you state the adjusters are 26tpi. Following on from this then the adjustments for a (non-Combat) Commando should be:-

The thread is26tpi thus each full turn gives 0.038â thus for 6 thou (inlet) turn 55 degrees - approx.6th turn. For exhaust (8 thou) turn 75 degrees or 5thturn.

Cheers

Submitted by mark_woodward on Sun, 18/03/2012

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Ref the above I made a small tool out of a PTFE sheet marked with the required 'pointers' - it drops over the tappet heads - just tighten until the adjusters don't move and back-off the required amount (easy with the squared adjusters) - not quite so easy with the inlets - - . For my first test I checked the measurements with feeler-gauges - they were cock-on (I won't use them again).

I tried the tool on my Rocket 3 and they were also 'cock-on'.

 


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