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too much tappet clearance after rebuild !   Message List  
Reply | Forward Message #41518 of 42301 |
Re: BSA too much tappet clearance after rebuild !

Hi pierre,

Different length. Bother! Thanks for this. Mystery deepens. But it doesn't seem
that one is too tight and the other too loose. I'll take them out and measure.
Does anyone know what the standard lengths should be?

Andy

--- In bsa@yahoogroups.com, "Pierre Michaud" <abaq4@...> wrote:
>
> Andy....best you go back to SRM and ask them to sort out the problem.
> Perhaps the new seats were cut too deep and or effective valve lengths are
> not to spec.
> Do not start fooling about with longer adjusters and rods etc. Note that the
> inlet and exhaust rods are a different length..........!!!!!!
> Pierre
>
> -----Original Message-----
> From: bsa@yahoogroups.com [mailto:bsa@yahoogroups.com]On Behalf Of
> bsa242
> Sent: Sunday, July 12, 2009 8:25 AM
> To: bsa@yahoogroups.com
> Subject: BSA too much tappet clearance after rebuild !
>
>
> hi all,
> have just had a rebore and rebuilt top-end. Reassembled, and to my horror,
> cannot reduce tappet clearance enough. SRM Engineering put two new valves in
> my head. Is it likely that they were shorter than my original ones?
> Any ideas would be most welcome on how to rectify this-can you get extended
> tappet screws? (I need about 4 more mm. Sorry, not so good on old English)
> This was my first ever big mechanical job and I'm a bit gutted to say the
> least.
> Looking forward to any ideas, Andy
>
>
>
>
> ------------------------------------
>
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>





Mon Jul 13, 2009 12:02 pm

bsa242
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Forward
Message #41518 of 42301 |
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hi all, have just had a rebore and rebuilt top-end. Reassembled, and to my horror, cannot reduce tappet clearance enough. SRM Engineering put two new valves...
bsa242
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Jul 12, 2009
12:24 pm

Longer pushrods would be a better solution, but you need to check the angle at which the rocker is pushing on the valve stem. Ideally it should be at 90° with...
iandusud
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Jul 12, 2009
1:33 pm

Thanks Ian, that makes sense. I'll make some enquiries this week. Andy...
bsa242
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Jul 12, 2009
3:55 pm

There's something well awry there.  Overlength pushrods should Never be required , and a 3/16" gap is pretty horrendous.  Try new adjusters and new,standard...
DAVID HOPWOOD
david265738
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Jul 12, 2009
5:27 pm

Hi Dave, I missed the bit in the original post about the 4mm clearance - that's a lot and if the push rods in there are std length then I think there would be...
iandusud
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Jul 12, 2009
8:00 pm

Cutting back valve seats is another reason that pushrods get shortened.  Cheers,   Dave. ... From: iandusud <booth.ian@...> Subject: Re: BSA too...
DAVID HOPWOOD
david265738
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Jul 12, 2009
8:20 pm

hi Dave, As well as the rebore, I've also had two new valves(and valve exhaust seat). Might that explain an increase in clearance? Andy....
bsa242
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Jul 12, 2009
9:10 pm

Andy....best you go back to SRM and ask them to sort out the problem. Perhaps the new seats were cut too deep and or effective valve lengths are not to spec. ...
Pierre Michaud
pierre_r_mic...
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Jul 12, 2009
11:19 pm

Hi pierre, Different length. Bother! Thanks for this. Mystery deepens. But it doesn't seem that one is too tight and the other too loose. I'll take them out...
bsa242
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Jul 13, 2009
12:02 pm

4mm?? Unless you used 3 or 4 head gaskets something is badly wrong. Did you strip the engine? Was the valve gear intact when you did the strip? If so have SRM...
beezabryan
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Jul 13, 2009
3:20 am

mate you wouldn,t be the first to get replacement parts that arent...quite the right size...for a 40-50 year old bike that has seen a heap of owners and...
Kevin Linville
shuswapkev
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Jul 13, 2009
11:22 am

Kevin, Your last comment hit it bang on for me! oh well, it's all good learning! andy...
bsa242
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Jul 14, 2009
12:05 pm

Hi Bryan, The bike is a B40 The old valves were very carbonised, lots of wear(so possibly 'riding high'into valve seats?) I stripped top-end and sent off to...
bsa242
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Jul 13, 2009
12:15 pm

Very likely that's it.  Replace the pushrods with new,standard items, and new adjusters just to be on the safe side, and that ought to be the end of the...
DAVID HOPWOOD
david265738
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Jul 13, 2009
5:33 am

You do have the Rupert Ratio book, I hope..... If not, get a copy,and that will tell you.  Don't start on a BSA Unit Single without a copy !    Cheers, ...
DAVID HOPWOOD
david265738
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Jul 13, 2009
5:05 pm

Hi Dave, Yes certainly have. it's been very good for a novice. THANKS ALL for your help in this- it's been much appreciated. Now to to take that head back off...
bsa242
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Jul 14, 2009
12:02 pm

Oddly enough, I've been making up some lash-caps today for a non - BSA engine,and although they should be supremely easy to make,that hasn't been the case in...
DAVID HOPWOOD
david265738
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Jul 14, 2009
6:34 pm
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