The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: duTch on 30.03. 2012 12:10
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Found an interesting thing?? Whilst setting up my timing today, before throwing the head on, I was covering all options and in the chaincase I noticed(see photo) a casting mark(red arrow) that unless it's my over-active imagination, or sheer co-incidence, and a bit of welding wire (with green tip )through the split pin hole aligns with perfectly at 5/16btdc- 32 degrees ('52 Plunger/alloy head,) Any clues on that??
Moving on,-Maybe this should be a separate topic?- I bought new valve springs, measured their length ok, when they arrived and figure all's sorted, but not the dia., and the caps that I have,(2nd/3rd photos), just don't look the part.
Big Springs are .070" bigger than the old ones on the O.D@1.371", and the small springs smaller, not so important.
The point is that there's not a lot of material holding the caps on and there's a fair slap of lateral movement up top. Old springs were bad enough, but new are more pronounced.
Do I have incorrect spring Caps????
Hope the photos explain a bit, there should be three (3)
Thanks duTch
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Re springs does this help ?
http://www.a7a10.net/forum/index.php/topic,4757.msg32740.html#msg32740
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Thanks Kiwi,
I think I dug that of the free google-net a while back when I was looking for info, but will have a better look later me brain's a bit frazzled at the moment,
It's actually the Caps that I'm wondering about. As far as I can figure out the ones I have should be correct, but seem too small and sloppy.
The new big spring OD is 1.390/cap OD is 1.190, that's 1 tenth all round bigger- that normal?
My new big spring ID is 1.091(old one 0.987), and the 'larger-inner diameter' on the cap where the spring sits is 0.955.
This is why the brain's frazzled!!!!!
Cheers duTch
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Dutch,
To me, your collars don't look right.
There are some useful pictures and dimension information on this site: http://www.basmotor.a.se/eng/index.html
Select "Engine" then "Valve Spring" from the selections at the top and you get to a page with a lot of collars properly (I think) identified, showing both sides and giving diameters.
Richard L.
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Thanks Richard,
I just came back to post that I found some pictures, same ones ta.I had the part number so just googled it Mine are the cast/A7 67-0034's,but I need 67-0960.
I looked at them a while back and didn't think they looked right.
Thanks again
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while not being familiar with the semi unit motors, take your time with valve caps/collets. Make sure you have this right.
There are a number of combinations/variations and differing collet/cap tapers.
I assumed mine were matched and ended up removing over 30 shards of collet as the tapers were different. The collets failing reduced valve spring pressure and bent several valves *eek* albeit on the race track.
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Hiya Rocket R.,
Ta for that, I've been measuring every which way, could've measured me way to the moon(in microns). I bought new collets in UK back in '81, but they didn't fit then, so I (think I) figured something was amiss,no ready available info, but the 'too hard' basket was handy.
When I bought new SR V.springs last year and I checked them for length- ok(I think, and will again), but not dia. *problem*,<-not a problem just a head banger! , something still didn't twig, and I dug out the collets again, but decided I must've got'm(2 sets ) for the M20 that I had a bit before then ! so- back in the 'hard basket' ?
It wasn't till I cleaned head up to reassemble, that I realized the collars I've been using were too small (ie totally wrong),and with research figure the new collets from'81,....surprise surprise (should) fit new collars!!!!! , However- have been checking/measuring the valves "every which way" again mainly the collet grooves, and the 'new' collets don't quite seat in there properly, so'm going to do a bit of 'dremel engineering' on them(collets). Kind of hard to explain, but they just have ridges round the inside just under the engaging 'lug'(see photo), and figure they should sit snug on the valve stem, not rickety rockety(nothin' wrong with rockets in the right place), as I figure it'll put extra pre-load on the springs if they sit too 'fat'??
Thanks Rocket and also KiwiGF I had another look at your story,useful but already covered. Cheers duTch (did this last night and left it,hope makes sense)
NB I never thought I'd get so involved in this -was supposed to be a pull it apart and ride in a couple of weeks