Hairpin valve spring nick

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Andy51
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Hairpin valve spring nick

Post by Andy51 »

Hi All, just putting my '54 18S cylinder head back together after grinding valves in. Got the springs in when I noticed a pronounced nick in the wire of one of the springs, about 10 thous deep. Don't know how it got there, but it looked fresh. The nick is in the part of the spring at the collet end, about mid-way in the straight bit between the coiled part and the loop that engages under the collet. I tried polishing it out but I think it's too deep for that. I know that nicks are stress concentrators that can lead to spring breakages, but I don't know how critical one would be in this position - a new set ain't cheap! Your opinions would be gratefully received. Thanks, Andy
56G80S
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Re: Hairpin valve spring nick

Post by 56G80S »

Andy

Not much help but I had something similar and from memory used a carborundum rod to smoth out and relieve any stress point but it wasn't as deep as yours sounds.

Done a lot of miles since and no recurrence or problem.

Johnny B
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Rob Harknett
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Re: Hairpin valve spring nick

Post by Rob Harknett »

Mine are well worn, have been for the last 30 odd years I've been riding the bike. I think they were S/hand off a jumble stall.
Mick D
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Re: Hairpin valve spring nick

Post by Mick D »

Hi

In the absence of a photo, I don't think I'd be concerned, I've seen plenty of photos of springs worn much more than this where they bear on the collet collar.

I'd be trying to identify how the damage occurred and making sure it won't happen again.

Has anyone ever seen one of these springs broken?

Regards Mick
Andy51
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Re: Hairpin valve spring nick

Post by Andy51 »

Hi All, thanks for your replies so far. I looked in Irving's 'Tuning for Speed' and he says that when hairpin springs break, they normally do so where the coiled bit transitions into the straight top leg that engages with the collar. My nick is about half way along the top leg, clear of the bend, so should be all right. I have a carborundum rod and like Johnny D, will polish out the nick and measure the resultant thinning of the spring before making final decision. The nick seems to have occurred during removal/replacement, despite using proper toll from club. In the meantime, if anyone else has any thoughts, would still be grateful for them. Andy
Mick D
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Re: Hairpin valve spring nick

Post by Mick D »

Hi

If you blend the damage it would be advisable to equalise the effect with a similar blend on the other side ;)

Regards Mick
G15 Roy
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Re: Hairpin valve spring nick

Post by G15 Roy »

New stock will be arriving by the end of this month.
Roy
Andy51
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Re: Hairpin valve spring nick

Post by Andy51 »

Thanks, Roy and Mick. I will see if it can be blended in without excessive weakening, if not, I can get a replacement when they arrive. It's not as if I'm going anywhere soon! Andy
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Re: Hairpin valve spring nick

Post by G15 Roy »

New Stock has arrived.
Roy
Andy51
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Re: Hairpin valve spring nick

Post by Andy51 »

Roy, thanks very much for the info but I got some on ebay - see my other current thread. Andy
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