Author Topic: A10 - Valves Springs - Help needed  (Read 418 times)

Offline Angusa10

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A10 - Valves Springs - Help needed
« on: 29.11. 2020 17:33 »
Hi Im new to forum.
Ive had my 1954 BSA A10 for some 47 years now.  17 when I got it and 19 when I stripped it down and put it in boxes for a retirement hobby.  It is a bitza - part flash , part rocket and like that when I got it.
So I’ve rebuilt it. Put it on the road. Within a few miles started smoking heavily both cylinders. Oil running out of the exhausts.  I was careful during the rebuild – it couldn’t possibly be from the cylinders thought I – so it had to be the valves and guides, yes?.
So I’ve stripped the head. Read everything I could find. Did a doctorate. Removed the valves and measured everything (carefully this time). Now apart from one exhaust valve diameter (which is borderline acceptable) everything is within spec.
So I’m now reconciled that the problem is indeed with cylinder bores, they are glazed - but not badly worn. So I intend to hone them and fit new rings. Ill try that.
[As an aside, high compression pistons are fitted, it is a "detuned" road rocket engine. Whilst stamped HHC, a standard cam is fitted, gearbox is standard too (not RRT2 unfortunately)].
With respect to the head,  I am going to treat it to new exhaust valves and new springs while it is apart and put it back together. 

Now my dilemma is related to the valve springs fitted.
I have a cast iron head.
My valve outer springs measure between 2.08 -2.10“ length ( cf 1.875” Haynes etc).  (the coil o/d is 35mm, i/d is 28mm, the wire is 3.5mm dia)
My valve inner springs measure between 1.85 -1.89”length ( cf 1.531” Haynes etc). (the coil o/d is 27mm, i/d 21mm, the wire is 3mm dia)
Whilst my springs are longer than those in the Haynes manual, they fit nicely on the cups and there is no evidence of there being any binding during their service.
So my questions to the forum (apart from WTF?) are:
•   From the info above,  Are my fitted  springs likely A10 super rocket ?.  [Haycraft gives A10 S/R  length outer dimension 2.125” and inner 2.00” so it seems likely]
•   I understand from various threads Ive read A10 S/R springs are lighter – but are they interchangeable with the A10 standard?. Do they have the same stiffness?.  Is it important? [ie cast iron vs aluminium head, valve dimensions etc]
•   And some advice please - what should I replace my spring set with – Like for like - or revert to the A10 standard set in which case are the cups compatible?

Thanks in anticipation

Online chaterlea25

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Re: A10 - Valves Springs - Help needed
« Reply #1 on: 29.11. 2020 19:01 »
Hi
Some photographs of the valves/ caps / collets  might help ?
Alloy head 650 valves have a semicircular groove for the collets, All other valves have a parallel reduced section
The alloy head valve parts will not work with the others on a standard setup
The outside diameter of the alloy head springs is bigger than the others
Maybe the head has had the seats opened out and larger headed valves and components fitted?
Apologies due to surgery last Monday I am unable to go to the workshop and measure up parts for comparison

You do not explain the extent of your "rebuild", please do?
If the engine did not initially smoke and did so after a couple of miles, I would suspect a problem with the oil not being returned to the tank ? did you check the return and oil level after the run?

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: A10 - Valves Springs - Help needed
« Reply #2 on: 29.11. 2020 20:40 »
G'day Angus  *welcome*
As John says there are a few variables when it comes to valves and springs. A pic of the top end will help.
As for the smoking and oil in the exhaust I would suspect valve guides, either fit in head of fit to the valves.

Now get over to Introductions and give us your story and what part of the rock your on.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Angusa10

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Re: A10 - Valves Springs - Help needed
« Reply #3 on: 30.11. 2020 09:50 »
Thanks guys,

I’ve attached a couple of photos of my valves and springs to my post. I think based on your comments John, that these are not from an alloy head. But would be pleased if you could confirm. There are no numbers on the valves.

The extent of the rebuild has been nut and bolt. I had the crank reground for an oversize bush rather than an SRM needle roller  - due to anticipated lower mileage. Otherwise new bearings seals etc - wheels rebuilt, electrics, new Exhausts fasteners etc etc. Done as much as I could in stainless. Hate chrome - find it heartbreaking when rust comes through.

Musky, I’m confident it is not the guides causing the smoke. Just before I stopped using it , all those years ago, I replaced the original bronze guides with new cast iron ones. Did it with my old man, head in the oven, guides in freezer. Vivid memories of hot and cold burns and colourful language. Also confirmed by my recent, Uber careful measurements. Only one valve stem is on the verge of being undersize. The bores and piston tops are wet with oil. So I think a hone and new rings will sort it.

NB the bores are perfect, not stepped, only glazed. I didn’t replace the rings during the rebuild, used the old ones. Gapped ok. I think that was my mistake.

Another thing, possible contributor, and worthy of note is my recent fitting of an external oil filter in the toolbox. I’m getting an excellent return flow to the oil tank, but wonder if I’m also getting the same / too much to the rockers. Is this possible. Should I choke the flow through the rocker feed with a clip?. Is this common?. ( if the hone and new rings doesn’t sort it).

Anyway back to the valve springs. I’m thinking I need to fit standard A10 GF springs provided the cups, collets are the same. Are the snaps good enough for you to tell?

 Any thanks to you both meantime.

Ps Will try to write an introduction shortly.


Online chaterlea25

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Re: A10 - Valves Springs - Help needed
« Reply #4 on: 30.11. 2020 12:22 »
Hi Angus,
Yes you have standard iron head caps, collets and valves, hopefully someone will check the spring dimensions??

If the oil was coming from the head, you will see traces  of it around the guides?
Are the correct banjo bolts with the restriction holes fitted?

Is the oil filter connected right  was round?

John

1961 Super Rocket
1963 RGS (ongoing)

Offline Angusa10

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Re: A10 - Valves Springs - Help needed
« Reply #5 on: 30.11. 2020 13:20 »
Thanks for that John.
In the old days you would have been able to slide the bits across the counter and check with the shopkeeper. No such luxury anymore. That's where this forum becomes invaluable. Ill order a set of new standard springs.

There was a build up of oily crud around the exhaust valves. Quite strange after only 30-40 miles on the road. Im not convinced this is due to guide/valve gap. Im hoping that with a hone new rings and spring set it will clear the problem.

The correct banjo bolts are fitted - as standard

Oil filter is correct way round on the oil return to tank.

Thanks so much. Iain

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Re: A10 - Valves Springs - Help needed
« Reply #6 on: 30.11. 2020 18:57 »
G'day Iain.
Just to make sure. The filter is fitted between the pump and the rocker feed take off? How much piston-bore clearance is there?
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

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Re: A10 - Valves Springs - Help needed
« Reply #7 on: 30.11. 2020 21:47 »
Hi Iain,
What I meant was that the filter unit is correctly connected regarding flow direction
the oil must flow in on the outside of the filter and out the centre

John
1961 Super Rocket
1963 RGS (ongoing)