Author Topic: Strange valve clearance  (Read 1520 times)

Offline Gasket4450

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Strange valve clearance
« on: 20.12. 2015 15:26 »
Hello again to all.   Its been a while since I had to post ( A7 with starting problems, but traced to magneto and put right by Groily for me - 700 trouble-free miles since...many thanks ). Out on Saturday poodling round the lanes when I thought I could hear a knocking from the front of the bottom end, not a rhythmic, every revolution kind of knock, but occurring randomly and without any sort of pattern. Limped home carefully, and felt around the front end and dynamo, where I convinced myself I could feel something knocking.  Switched off, and called my more experienced mate, and we did the ' mechanics stethoscope ' trick with two big screwdrivers, although by now the noise had stopped. All we heard was tappet rattle !
                            Anyway, took the inspection covers off the rocker box this morning and checked the clearances. Both exhaust valves were within a couple of thou of 16, so re-set those. Left inlet was still on 10, but right inlet was about 1/4" .....!!!  Oh, oh.  I had to screw the adjuster down so far into the rocker to get to 10 thou clearance, there was no thread left to put the locknut on.  It was not like that when I put it together, and all rockers and pushrods seem to go up and down as they should. I put new valves and guides in when I built the engine last year, new alloy pushrods from Brit Only in Austria
( got fed up with people in this country telling me that A7 rods were the same length as A10...).
                            Right inlet valve does not appear to be sticking, and returns the same distance as the left. Spring pressure feels the same on both valves. My problem is this:  the bike was running okay until I heard this odd noise, and now there seems to be something definitely not right.  Other than perhaps a sticky valve, or a bent pushrod, what other disasters might I discover ?  Disintegrated cam follower ( do they do that? ). 1/4" gone off the bottom of one of the pushrods ( don't think they do that either, do they ? ) Catastrophic failure of the cam shaft ? Then I guess the engine wouldn't run at all if it was the cam ( new 357 cam, iron head, 1959 model). Certainly 1/4" seems to have disappeared from somewhere, and I am at a loss to explain where it has gone  ( maybe the wife has got it, she's always complaining about an extra quarter of an inch !!)  If I have to take it all apart, then so be it, but I though I would ask first before getting the spanners out.  Anybody with any similar experience out there, please?
ATB
Norman
1960 A10, alive and thriving. 1959 A7 living on borrowed time !

Online terryg

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Re: Strange valve clearance
« Reply #1 on: 20.12. 2015 16:10 »
http://www.a7a10.net/forum/index.php?topic=8777.msg63854#msg63854

Searched 'alloy pushrod' and found the above, amongst other posts.
Terry
'57 'SR', '59 SR, '63 RGS

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Re: Strange valve clearance
« Reply #2 on: 20.12. 2015 16:14 »
Hi Norman,
With a bit of luck you will find that the pushrod has worn, (plenty examples of that happening on here *sad2*)
Remove the sump plate and look for debris, if alloy only bits there than more than likely the pushrod
If there are shiny magnetid particles thare then the problem may be more serious *????*
So check these out first before we come up with any worst case scenarios

HTH
John
1961 Super Rocket
1963 RGS (ongoing)

Offline Rocket Racer

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Re: Strange valve clearance
« Reply #3 on: 20.12. 2015 19:50 »
I think John's on the ball, I'd want to inspect that pushrod, which is a rocker box off job and 3 new base gaskets.

Something is wrong, tappet clearances don't increase to 1/4" unless a lock nut wasnt locked, the question is where have you lost that lift.
An alloy pushrod (catastrophic wear or more likely bent) is by far the most likely as you cannot have lost that height off the base radius of the cam and you mention the cam is still lifting the valve fine with the adjustment taken up.

Once the rocker box is off you should be able to identify the problem.
Tim


A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline Gasket4450

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Re: Strange valve clearance
« Reply #4 on: 21.12. 2015 17:52 »
               Terry, that previous post you found is spot on, even down to the missing 1/4"  ( ooh, er missus ). I shall start dismantling from the top and see what we come across. Certainly sounds like alloy push rod failure. Pity, I thought they would be okay, coming from BritOnly, but there you are. Perhaps they are manufactured by the same British company mentioned in the other post...!!

Tim/John,
                        thanks for taking the time. It looks as though I am suffering from the same dreaded alloy pushrod malady that others have come across before me.  May have to bite the bullet and pay out for a steel set from SRM. Will post when I have delved a bit deeper, but certainly looks as though you Forum guys have put your finger on it for me. Much obliged.
Merry Humbug
Norm
1960 A10, alive and thriving. 1959 A7 living on borrowed time !

Offline Gasket4450

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Re: Strange valve clearance
« Reply #5 on: 26.12. 2015 16:40 »
Merry Humbug to One and All,
                                                   Well, you blokes out there were dead right with your diagnosis. Having taken the top end apart, guess what I found......? Yep, one inlet pushrod was 1/4" shorter than the other, as described in previous posts by other unfortunates. The picture shows what I found.  Anyway, I was so convinced you were right with your theory, I ordered a steel set from SRM on Tuesday at lunchtime, they arrived on Wednesday morning. How's that for service in Xmas week?
                         So, next the job we all love so much....rockerbox  replacement. I have done it in about ten minutes before, but normally it takes me an hour or so of fiddling. Still, better than being made to watch a Christmas omnibus edition of Eastenders, eh?

                         Once again, thanks to all.

Norm
                       
1960 A10, alive and thriving. 1959 A7 living on borrowed time !

Offline Dean

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Re: Strange valve clearance
« Reply #6 on: 26.12. 2015 19:31 »
Hi Norm
I'm glad you found the problem. I suppose the issue now is why has one shortened? I'm running alloy pushrods on both my A10s with no such problem. Is it simply that there are some around that are not made of the proper alloy?

I can't bear Eastenders but I'd still be pushed to choose between re-fitting the rocker box and being forecd to watch it that programme  *conf*
Never tell people your troubles. Half of them are not interested and the other half are glad you're getting what's coming to you.

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Re: Strange valve clearance
« Reply #7 on: 26.12. 2015 19:50 »
I expected to see one of the pushrods with a shmooshed end, not two ends still nicely rounded. Are we looking at a uniform wearing down in the lifter or rocker cup, or was one just shorter going in? Can someone explain?

Richard L.

Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

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Re: Strange valve clearance
« Reply #8 on: 26.12. 2015 22:00 »
Hello Norm, my alloy pushrods continue to serve me well as paint stirrers.

Remember - recover, recycle, re-use!

Pleased your problem was diagnosed at the early, less expensive, stage.

Happy New Year.
Terry
'57 'SR', '59 SR, '63 RGS

Offline Rocket Racer

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Re: Strange valve clearance
« Reply #9 on: 27.12. 2015 02:16 »
couldn't say it better
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline bikerbob

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Re: Strange valve clearance
« Reply #10 on: 27.12. 2015 09:15 »
This problem with alloy push rods goes back a long time. I remember back in 1995 when I was restoring my Gold Flash  the first set of alloy push rods I bought did not last more than one year before the ends were wearing away I replaced them with another set and had problems starting the bike traced back to the inlet ones being too short I contacted the director of the company who made them just really to inform them of the problem but even after I sent them the alloy rods back plus an original steel one to prove the point . I received a letter back plus the rods I had sent claiming that they had been making these rods for number of years manufactured from BSA drawings and had no complaints and suggesting that if not satisfied with their products I should go elsewhere. At the time I did contact the then Technical Consultant  of the BSA owners club and he confirmed that there had been problems with some of these alloy rods also a dealer also admitted that they had received rods from this company with the same problem as mine.

Offline Gasket4450

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Re: Strange valve clearance
« Reply #11 on: 27.12. 2015 20:17 »
Hi Richard.
                      In answer to your query - the rods were the same length going in. I had trouble getting A7 rods in this country, some 'established suppliers' even telling me A7 and A10 rods were the same ! ( But we know different, don't we boys and girls ?). I won't name names on this occasion. However, if you enlarge the photo ( not the best, I agree ) you can just make out a tiny 'tit' on the top of the right hand rod, as though the end had been stretched and snapped, so not really sure what happened. I have removed the sump plate and flushed the sump out, and there was a tiny bit of metallic-looking sludge in there.
                        All in all, not a very good showing for the alloy rods after only 700 careful miles. Anyhow, the steel ones are in now, so will report later ( still have an A10 with alloys in, 1650 miles with no problems yet). Maybe just unlucky with these.
Regards and thanks for all good wishes
Norman
1960 A10, alive and thriving. 1959 A7 living on borrowed time !

Offline Rocket Racer

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Re: Strange valve clearance
« Reply #12 on: 27.12. 2015 22:59 »
Also worth considering that an alloy push rod will expand at double the rate of a steel one. Now I'm no engineer but that sounds like it might reduce tappet clearances although probably only a thou or so  *dunno*
Alloy push rods really makes sense when fitted with both an alloy head and an alloy barrel.

I run alloy push rods in my race motor and steel in my road motor, funnily the alloy rods seem to be simpler to locate when assembling the rocker box, where I need the comb for the steel ones.
The alloy ones came with the motor though I didnt buy them.

The bottom ends of the alloy rods will be very sensitive to anything abrasive in the cam follower cup. I recall having a problem thirty odd years ago with a tigress motor that ate an alloy pushrod and there was a tiny piece of grit in the cam follower

certainly worth putting some assembly lube  in there on assembly and some oil for that matter.
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline Gasket4450

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Re: Strange valve clearance
« Reply #13 on: 26.01. 2016 15:56 »
All is well again.  The new pushrods are in, and everything turns over very nicely again.  Went out for a short ride yesterday with no problems. Engine is much quieter now with 8 and 10 thou clearances on valves, in view of the 357 cam, instead of the noisy 12 and 16 I was running on previously. In fact the motor is so quiet it ticks over like a little sewing machine now
 ( perhaps the wife would like to run up a pair of curtains or something on it....)
                   Top tip about the paint stirrers, Terryg, I now have a matching set just like yours !!

All the best for the approaching new riding season ( for those of us in the Northern Hemisphere, that is.....)
Norman 
1960 A10, alive and thriving. 1959 A7 living on borrowed time !

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Re: Strange valve clearance
« Reply #14 on: 26.01. 2016 20:21 »
I've just acquired an Ariel  H'master and because of the similarities with A10 engines enjoy delving (tresspassing ) into this forum. I've already found the answer to a sludge trap query. I found this thread  interesting, and just wondered why the A10 rocker box doesn't have an access plug on top like the Huntmaster. I wouldn't have thought it a difficult mod to fit one, or am I missing something.
regards

60'Matchy G12
58 AJS 18s
58 Ariel Huntmaster]