Use of coil valve springs instead of hairpins on H/W singles

Helpful information and requests for assitance and advice
LynP
Member
Posts: 335
Joined: Mon Jan 01, 1990 12:00 am
Location: GWENT UK

Use of coil valve springs instead of hairpins on H/W singles

Post by LynP »

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?
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by SPRIDDLER »

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 a tide in the affairs of men
Which taken at the flood............'
LynP
Member
Posts: 335
Joined: Mon Jan 01, 1990 12:00 am
Location: GWENT UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by LynP »

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.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by SPRIDDLER »

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.
'There is a tide in the affairs of men
Which taken at the flood............'
OEW591
Posts: 158
Joined: Mon Jan 01, 1990 12:00 am
Location: CAMBRIDGESHIRE UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by OEW591 »

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!
56G80S
Member
Posts: 3354
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by 56G80S »

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
MikeM.
Member
Posts: 1906
Joined: Wed Jan 01, 1992 12:00 am
Location: SURREY UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by MikeM. »

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.
User avatar
1608
Member
Posts: 2493
Joined: Mon Oct 05, 2009 1:00 am
Location: ESSEX UK

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by 1608 »

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.
RayBeech
Member
Posts: 70
Joined: Sat Nov 08, 2014 5:16 pm
Location: Lincolnshire

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by RayBeech »

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.
User avatar
Expat
Member
Posts: 1033
Joined: Thu Nov 12, 2015 2:22 pm
Location: Tennessee, USA

Re: Use of coil valve springs instead of hairpins on H/W sin

Post by Expat »

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.
Keep shiny side up.

These are my principles, if you don’t like them, I have others. (Groucho Marx)
Locked