The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: bsa-bill on 01.05. 2015 11:30
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Changed the Rocker box on the Flash with a spare one I had (as previous post - Rocker box cracked and rocker shaft on two bits)
All went well - box on - push rods in place - replaced the single tappet adjuster that I removed to take pressure of original box when I removed it.
was Surprised how far I needed to screw the adjuster down to get correct clearance, in fact I had to remove it and screw the nut up over part of the square on the top, tried the other three and found them all the same.
Got a set of the the type with a hole in the top or an allan key ordered so that will solve the problem (I'm not happy with the lock nut that far up the threads that half of it is only on the threads on the corner of the square)
Anyone had this before or got an explanation?
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If your previous rocker box did not have the same problem (which implies you do not have worn cams or followers, or push rods that are too short) I reckon it definitely needs to be looked into.....the tappet adjusters should not be sticking out too far on the valve side as that will cause wear I suspect......sorry to ask but you are 100% sure the push rods properly in place both ends and the rocker box is fully down on the head?
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but you are 100% sure the push rods properly in place both ends and the rocker box is fully down on the head?
Thanks for the suggestion - seemed to be all fine, certainly all the adjusters are the same, pushrods spin freely and everything works as it should when turning the engine over, I have a camera thing that connects to a lap top, might show down the pushrod tunnel otherwise it looks like taking the box off again, bit of a pain but better safe than sorry
but as I'm waiting for the Postie delivering new adjusters ...............
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The only explanation I can offer is, maybe the R/box head interface had been shaved more on the old one ...??? (I think I got that the right way round)
I have the Allen key adjusters, they make it much easier, but the locknuts are also towards the top (but no so far to cause alarm).
When I checked the gaps last time (all surprisingly good), I was looking at the angle of the rocker arms to the valves to see if they all had an ideal geometry (~90˚ mid-stroke?), same principle as the clutch or brake arms- main reason is because I replaced the pushrods, but I think they're a bit shorter than the others....still haven't followed it up....took photos for later look but by that time the brain was spazzled *eek*....
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Very strange, Bill. Further investigation required.
Be very careful doing the locknut up on the cheaper allen key type adjusters. I have had a few snap when tightened *eek* I'd hate to think of the damage if one let go in service.
Cheers
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Thanks for all the replies lads.
Sun came out again so Garden has priority at the mo.
Gave the box a comparative measure with old fashioned callipers and imagined some small difference but not to accurate.
As everything seems in order I think I need to remove the box and see if I can find anything if not then lift the barrels and check the camshaft.
note for future - check tappet clearance before removing rocker box ;)
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took the rocker box off this afternoon, all is as it should be pushrods located correct both ends.
Compared the box with the one I took off, no difference in the height of it as far as I can see, or the position of the rocker shafts although not too scientific a measure.
However the casting number under the box is interesting the one on now 67- 208 but the original one looks like 67-308 very difficult to be certain with cast numbers tho.
anyway as I'm this far I have the head off and will lift the barrels tomorrow and look at the camshaft, doubt if I'll find anything (hopes) but nice to have some confirmation
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gave Peebles (Borders and Lothians MC) show a miss this year, had a heavy week walking about, my jippy knee was in dire need of a rest so watched Moto GP and had the late afternoon in the shed (heater on Brrr) took the barrels off, camshafts is fine as are the followers so I'll give them and the head a lick of engine black this afternoon, hopefully the new tappet adjusters will arrive tomorrow and I'll get it all back together.
Bit of work for nothing but at least I know nowt's amiss
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Bill, I just had a thought that if you used a thicker gasket might affect the setup a bit...?
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thanks dutch, the big gasket on the inlet side stayed put and was undamaged so I left it where it was, I did change the exhaust ones, used a smear of grey silicon but not too much I think.
The casting numbers of the box's being ( I think ) different makes me think there may be a small difference in the distance from the rocker shafts to the base of the box, probably wouldn't take more than a few thou there to make some difference to the adjustment.
However as all the adjusters are needing the same sort of length and the camshaft is nice and smooth with no lip on any of the lobes I'm happy to put it back together.
thanks all for the input
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G'day Bill. There were only two rocker box's both with the same # but the one for the SS/SR had a different # stamped over it.
Cheers
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thanks Musky - No over stamping , so it's telling the difference between a cast 2 or 3, and if you say there was only one then that rules that one out, valve recession would have the opposite effect on clearance, and if it was wear on the cams or followers then as ALL the adjusters show the same thing it that would be unusual I think.
Can't see anything to be concerned about so I'll put it together with new type adjusters and ride it and do regular checks to see if there's any movment.
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Bill ,what Dutch said re thickness of gaskets rang a distant bell with my memory. I remember one weekend having to put the r/box back on and used an homemade set up which raised things to worse than yours couldn't adjust the tappets had to wait til the dealer opened next day and with standard gaskets all was as should be , still leaked though !! *smile*Bob
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Thanks Bob, exhaust (front) gasket are standard, the inlet rear is made from gasket paper about the same thickness but maybe a bit harder so might not squish down so much.
Things is any extras thickness has a double effect as it lifts the rocker tappet off the pushrod a tad and away from the valve by a similar tad, so two tads worth
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a tad and away from the valve by a similar tad, so two tads worth
...two tads'd be a tur ...?..um actually that could be deceptive, but when I was trying to determine if I needed longer pushrods, I measured the rocker arms (well tried in a rudimentary fashion), and came up with one arm on each being longer than the other by as far as I can gather from my 'jottings' about 1/4", but forget which way...no great surprise, but I ended up taking what I could get anyway...
Point is, taking the lever/ratio into account; one tad would be a tad bigger than the other tad, so dere's a tird tad.... *????*
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yep - every little tad helps
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To conclude and also a little guide to anyone faced with a stripped stud hole for the rocker tappet covers.
I spent this weekend and Monday suffering a nagging toothache, not the worst pain I've had but enough to annoy, this morning though it went to a different level and the dentist was phoned when MT wife (ex nurse) diagnosed an abscess, I couldn't swallow without excruciating pain, so here I am dosed up with antibiotics and pain killers that make a session in the the shed extremely problematic, even if I could walk straight enough to get there, so thought type a conclusion to the rocker box thing (right whine over)
Rooting around in the bottom shed I came upon a very nice vapour blasted rocker box, made me wonder why I'd never used it then on further examination it became clear why not, lots of stripped threads, well it looked so much better than the one I'd used (to replace the cracked one), so I set about repairing the threads, all went to plan except for the bottom stud hole on the EX side of the box, it looked strange - cock-eyed, anyway I attempted to drill it straight with the correct drill for a hellicoil, OK sort of, but the tap didn't work at all, kept jumping, looked like there was a cinder or something in there which probably explained why it had been drilled so far of true.
At this point I should profess that in the words of the great late North East comedian Mr Robert (Bobby) Thompson when asked by his wife to put a new string on her carrier bag (pre plastic) he proclaimed "why am not an engineer"
So a bodge was required, I drilled the hole out with the biggest drill I could, drilled right through and filled the hole with metal putty allowing it to protruded out of the bottom of the hole and sculpted the over flow kind of neatly, gave it 24 hours to dry then used an old rocker box cover to find out where to centre a drill and guide the direction, used a wood drill (with the little point on) as the putty is hard but powdery to drill and a sacrifice of one wood drill seemed fair enough.
did not need to increase the size of the hole for the tap, tricky bit was keeping the tap square, inserted the helicoil.
Tap was not far off, I had to very slightly ease the hole in the cover but not much at all
pictures hopefully tell the story
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pictures hopefully tell the story
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G'day Bill.
The original repair bodge of that stud hole looks odd. Is that weld build up underneath?
Cheers
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No Muskrat that is metal putty, my thinking was that as it's an area not seen a surplus of the stuff down there would give some stability to the stuff in the hole (which I had drilled right through) and prevent the possibility of it turning in the hole when I tapped it,
It is quite easy to work, and I would think well up to the small amount of torque required in that location/task.
I did consider using two inserts (one size up and 1/4 one inside the other) to give more area of contact between insert /putty,
Probably filling the hole with weld would have been ideal but beyond my skills or equipment
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G'day Bill.
I see your reasoning. My only concern is the restriction of air flow over a hot part of the motor. But then it might act as a ram air and work better. *grins*
Cheers
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My only concern is the restriction of air flow over a hot part of the motor.
Ah - didn't give that a thought but then here in Blighty probably not an issue 99 days out of 100