Author Topic: new to the forum  (Read 2328 times)

Offline Colsbeeza

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Re: new to the forum
« Reply #30 on: 21.10. 2021 12:19 »
Welcome 865,
 Anything you want to know about rigids - don't ask me!!  *grins* Swinging arm only.! However here is the place for experts.
Col
1961 Golden Flash
Australia

Offline 865

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Re: new to the forum
« Reply #31 on: 21.10. 2021 12:37 »
Thanks Swarfy, I'll change the head over. Would the wide fin head fit a swingarm motor? Cheers
Pete
WA

Offline 865

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Re: new to the forum
« Reply #32 on: 21.10. 2021 12:45 »
Any chance anyone could post pics of wide and narrow fin heads so I know what to look for
Thanks
Pete
WA

Offline Swarfcut

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Re: new to the forum
« Reply #33 on: 21.10. 2021 13:52 »
This is where it gets complicated.....

 Early plunger bikes have barrels and heads with narrow or thin fins. The number of fins stays the same, its the profile that changed. On the introduction of the S/A Range BSA increased the fin area to improve cooling. Wide fin heads and barrels were fitted to later (post '53 or thereabouts) Plunger bikes on both A7 and A10 Models. Gaskets and head bolt spacings are the same for early and late motors.

 A10  Plunger head thin fin casting number is 67-251, found on the underside of the inlet manifold.

 A10  Wide Fin Plunger and S/A Iron Head Casting is 67-1066, usually on the underside of one of the lower fins.  Both thin fin and wide fin heads have a combustion chamber diameter of 70mm. If it measures 66mm, it's A7. Barrel fins match the head profile.

 Other important points. Rocket and Shooting Star have their own expensive Alloy Heads. A7 barrels have a narrower bore, 7 fins and no cut outs to the lower spigots. Head gaskets differ to reflect smaller bore on A7 models.

 Swarfy.

Offline 865

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Re: new to the forum
« Reply #34 on: 21.10. 2021 14:09 »
Cheers Swarfy thanks for the explanation. Will the wide fin head work with the narrow fin barrels though?
If not I will still recon it anyway as someone may need one. Thanks
Pete
WA

Offline Swarfcut

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Re: new to the forum
« Reply #35 on: 21.10. 2021 14:30 »
 Yes it will. Exhaust pipe fitting is the same, it just looks odd.  That parts catalogue will be a well thumbed and very worthwhile purchase., you can see which bits are common across the range. Don't bother refurbishing parts you won't use. Your hard earned cash and  sweated labour becomes someone else's bargain. A quick wash off is all they need if being sold on.

 Swarfy.

Offline 865

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Re: new to the forum
« Reply #36 on: 21.10. 2021 15:15 »
Thanks again Swarfy. I'll use it til the right one comes along and I don't mind fixing things up and passing them along never know I might get a good swap lol. Thanks again.
Pete
WA

Offline Greybeard

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Re: new to the forum
« Reply #37 on: 23.10. 2021 12:14 »
Wide fins on my 1955 Plungie. I believe they are original.
Greybeard (Neil)
2023 Gold Star
Supporter of THE DISTINGUISHED GENTLEMAN'S RIDE https://www.gentlemansride.com

Warwickshire UK


A Distinguished Gentleman Riding his 1955 Plunger Golden Flash

Offline 865

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Re: new to the forum
« Reply #38 on: 24.10. 2021 10:07 »
White vinegar bath for the rust on the head. Learn something new everyday.
WA