Author Topic: Tappet clearances  (Read 1588 times)

Online wortluck

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Re: Tappet clearances
« Reply #15 on: 10.09. 2018 07:18 »
Iron head mate.  Could be they've found a 'wider' spot, will double check again when winter properly sets in.  I'll put up with the racket if the bike goes like it did yesterday. *smile* *smile*  TBH, they sounded loudest when I was off the bike, helmet off, listening to it quite closely!!!???  There was a bit of noise on hard acceleration, but the bike flew and it wasn't a 'serious' noise.  The adjusters look as if they've seem some action, but someone suggested replacing them only when the valves are replaced.  I'll have a listen to them when it's cold and see if they're worse - the logic being that if they close up when hot, they should be a bit louder - the bike did get hot *roll* despite being caught in a downpour for twenty minutes and temps dropped out on the Moors *angry*

By the way, can I use 'mushroom head' adjusters or stick to the original type?

Get that beer in mate - brain food! *beer* *countdown*
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Online JulianS

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Re: Tappet clearances
« Reply #16 on: 10.09. 2018 09:19 »
factory service sheet from 1959 on tappet clearances below.

Eddie Dow recommended 10 inlet and 12 exhaust with 357 cam.

Mushroom adjusters work OK but dont change the tappet rattle. They have to be fitted from under the rocker so the box has to come off to fit.

Online wortluck

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Re: Tappet clearances
« Reply #17 on: 10.09. 2018 16:19 »
Cheers Julian, very helpful, has anyone tried the ignition timing settings in the service sheet?

Tappets were a tight 10 on inlet and loose 13 on exhaust (didn't have a 14 feeler and the next one up was over 16).  I want to go for maximum power so the larger settings are good for me regardless of noise.  I don't want to disturb the rockerbox for the sake of mushroom heads so I'll get a set of Allen key items with standard heads.  They need to be replaced as the square tops are almost impossible to get to with a spanner on two of the adjusters and they're all chewed up anyway (from previous owners, I hasten to add).

Still time to get some riding in before the darkness falls! *smile*

'62 Flash
'49 B31
'59 BMW R60
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Motorcycles - transport of the Gods 😁 Beer - food of the Gods!😎

Online muskrat

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Re: Tappet clearances
« Reply #18 on: 10.09. 2018 20:19 »
G'day wortluck.
If you buy allen head adjusters get good ones. I've had two cheap (ebay) ones snap when the lock nut is tightened.
When they talk of more power at higher tappet settings their talking about top end revs for sustained periods which cause the gaps to close up considerably from the heat.
When I was racing the A7SS I'd start at std settings and do a few laps. The gaps would close up about lap 3 or 4. I had to give them an extra 2 thou".
Cheers
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Online wortluck

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Re: Tappet clearances
« Reply #19 on: 10.09. 2018 20:45 »
Cheers Musky

Any suggestions as to who supply good quality adjusters?

I don't thrash the nuts off the bike but I do like to get on with it, rattling up and down gears and often plenty of throttle.  It's an iron head so I'm thinking 10 and 14 would be about right - does this sound about right to you?
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Online JulianS

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Re: Tappet clearances
« Reply #20 on: 10.09. 2018 20:52 »

Offline trevinoz

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Re: Tappet clearances
« Reply #21 on: 10.09. 2018 22:20 »
I don't know what BSA were thinking when they set the advance to 13/32".
Back in the 60s when we had real petrol the engines used to ping terribly at that setting.

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Re: Tappet clearances
« Reply #22 on: 10.09. 2018 22:40 »
Cheers guys.  I've clocked the SRM kit and it seems good at £29 inc postage.

I take it the timing is best at 5/16" then.

Any more recommended settings for the valves, or should I see how I go on 10 and 14?  Seems to run really well on those at present - very pleased no more pinking.
'62 Flash
'49 B31
'59 BMW R60
FS1-E, YB100, RS100, RD200DX,250DX,350B, XS750


Motorcycles - transport of the Gods 😁 Beer - food of the Gods!😎