Use of coil valve springs instead of hairpins on H/W singles
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Use of coil valve springs instead of hairpins on H/W singles
Please can anyone give me some information about the use of coil valve springs on late heavy weight single heads;(1958ish) instead of the hairpin set up normally found. I would like to know what parts would be needed for that set up ie. springs, seats, top collars etc.
I am sure I read about this at some time in relation to the ease of finding coil springs rather hairpins on trips abroad should they be needed. Also hairpin springs are expensive now, so would such a conversion also be cheaper?
I am sure I read about this at some time in relation to the ease of finding coil springs rather hairpins on trips abroad should they be needed. Also hairpin springs are expensive now, so would such a conversion also be cheaper?
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Re: Use of coil valve springs instead of hairpins on H/W sin
I can't answer your specific question but are the hairpin springs worn out?
There is an acceptable measurement for the distance between the open parts (the 'jaws') of the hairspring when it has been removed. I.e between the two spring 'cut off' bottom ends that sit on the spring baseplate and the continuous top bend (where the top collar fits). Check also the part of the spring where it contacts the top collar for excessive wear.
It is: Acceptable gap 2". Replace when less than 1 11/16". That's quite a liberal tolerance.
The Venerable 'ITMA', late of this parish, had a mantra which generalised that: 'A half worn original part is more than likely to fit better and outlast a new pattern part'.
My practical advice would be that if the bike's been running o.k. and the measurements come close to the min figure and exhibit acceptable physical wear and you're not planning to pack a tent and tour the Middle East for 6 months then stick with the existing hair springs and take a spare part-worn spring when touring to guarantee that you won't need it
There must be quite a few 'old' springs available in sheds and although it must happen I have never heard of a spring failing completely.
There is an acceptable measurement for the distance between the open parts (the 'jaws') of the hairspring when it has been removed. I.e between the two spring 'cut off' bottom ends that sit on the spring baseplate and the continuous top bend (where the top collar fits). Check also the part of the spring where it contacts the top collar for excessive wear.
It is: Acceptable gap 2". Replace when less than 1 11/16". That's quite a liberal tolerance.
The Venerable 'ITMA', late of this parish, had a mantra which generalised that: 'A half worn original part is more than likely to fit better and outlast a new pattern part'.
My practical advice would be that if the bike's been running o.k. and the measurements come close to the min figure and exhibit acceptable physical wear and you're not planning to pack a tent and tour the Middle East for 6 months then stick with the existing hair springs and take a spare part-worn spring when touring to guarantee that you won't need it
There must be quite a few 'old' springs available in sheds and although it must happen I have never heard of a spring failing completely.
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Re: Use of coil valve springs instead of hairpins on H/W sin
Hi SPRIDDLER, thank you for your reply and I agree with you on the use of pattern parts. However, the reason for my question was that I have a 1958 G3LS fitted with the coil spring set up head which is in good working condition but I have always wondered what the parts used were from. I bought the bike in the late 1970,s and that is how it came to me. I was once told that the factory did fit some heavyweight singles with a coil set up so I finally decided to try to put my mind at rest. I am not aiming to go abroad with, it but could see that as the item I read suggested that at a push a suitable replacement coil spring would be easier to find than an hairpin given that situation.
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Re: Use of coil valve springs instead of hairpins on H/W sin
I'm with you now, Lyn. I had assumed that you thought you had worn out hair springs. I've no hands-on experience of swapping spring types.
Hopefully I'll learn something in due course in a post from someone who does know.
Hopefully I'll learn something in due course in a post from someone who does know.
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
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Re: Use of coil valve springs instead of hairpins on H/W sin
My 1965 Model 18 cylinder head was converted to coil springs by James Holland Racing in Bristol before I bought it. I don't know if they are still trading. They may be a source of information if they are.
The coil springs are still in there and haven't caused any issues. I have no idea of the spring specifications!
The coil springs are still in there and haven't caused any issues. I have no idea of the spring specifications!
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Re: Use of coil valve springs instead of hairpins on H/W sin
I thought quite a time about this after the expensive work I had done on the head last year. I re-fitted the current hairpin springs as they were inside the tolerance that I think was quoted in the Army sheets I found on Christian's Archives.
ther was some weaar where the collect holed thing (can't look up the right word, I'm in Italy at present. I thought this topic had been covered before as I think I considered switching to coil springs.
Yes there are threads on the search - I used haipin coil spring and some came up.
There was reference to a kit supplied by Russell Motors going well after 12.000 miles and being a straightforward swap.
Johnny B
ther was some weaar where the collect holed thing (can't look up the right word, I'm in Italy at present. I thought this topic had been covered before as I think I considered switching to coil springs.
Yes there are threads on the search - I used haipin coil spring and some came up.
There was reference to a kit supplied by Russell Motors going well after 12.000 miles and being a straightforward swap.
Johnny B
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Re: Use of coil valve springs instead of hairpins on H/W sin
I was sold a conversion kit many years ago by Les at Russell Motors and he assured me there wouldn't be any problems using them. unfortunately since fitting them I put a hole in the piston on the Cornish Jampot and have yet to run the bike again, that's the trouble with having other bikes that you can either ride or they too need attention.
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Re: Use of coil valve springs instead of hairpins on H/W sin
I was always lead to believe that hair springs were preferred in racing circles of the day. I too have never heard of one ( not showing undue wear) breaking . I haven't heard of any advantages in swapping to coil springs. Hair springs may appear antiquainted but they seem to do the job.
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Re: Use of coil valve springs instead of hairpins on H/W sin
I have a G3L that may have a 1939/40 AJS Iron head and it was born with coil springs, I am sure Rob Harknett will know what years had coil springs anyway, other than the standard at the time I don't think it matters which type are used as far as reliability goes (all the twins had coil) but as the lads have said Hairpins are as reliable.
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Re: Use of coil valve springs instead of hairpins on H/W sin
I have a collection of used hairpin springs that came with the bike, so now I'll have to check the dims out of curiousity.
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