Author Topic: Problems mounting Hunt Mag on a10  (Read 1914 times)

Offline Fast 58 BSA

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Problems mounting Hunt Mag on a10
« on: 20.09. 2011 12:23 »
I recently bought a used Joe Hunt mag for my A10. Now when trying to mount it, the magbody interferes with the enginecase (by the rear cylinder studs) to the point where it won't fit properly. *angry* I know when you buy used stuff, you sometimes don't get the right thing, but this is a pre-unit model and matches the ones I have found on the hunt webpage. I am a newbie at wrenching on britbikes and have little familiarity with magnetos. Is there something obvious I am not understanding when trying to mount it? Any adjustment that can be made to the mag body to solve the problem short of grinding it? I am not keen on grinding away on the engine case as the material already seems rather weak around the cylinder studs

Thanks for any guidance
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Telemark, Norway

'58 Golden Flash project bike - reborn as angry dual carb cafe racer/rgs rep

Offline a10gf

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Offline Fast 58 BSA

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Re: Problems mounting Hunt Mag on a10
« Reply #2 on: 20.09. 2011 20:53 »
Thanks for the thread. We're abouts are you in Norway? I am located in Telemark. After some careful internet searching, it looks to me that I have an older mag (surprise! Bought it used...) and that it will fit a Norton pre-unit, but not my A10. Oh, well. File  under "thought I got a good deal, but didn't".  Cheers
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Telemark, Norway

'58 Golden Flash project bike - reborn as angry dual carb cafe racer/rgs rep

Offline a10gf

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Re: Problems mounting Hunt Mag on a10
« Reply #3 on: 20.09. 2011 22:12 »
offtopic: Bergen, homepage: http://www.a7a10.net/BSA/BSAGoldenFlash.htm , and it was all the questions I received by email that made me think about starting a forum. Didn't get it that you are from Norway, (quote from the reg. agreement: please state WHICH COUNTRY YOU LIVE IN). Maybe post a few photos of the bike in Bikes, pictures and members ?

btw, a picture of the problem with the Hunt may help, maybe Frenchy can inform what he did to make it fit.
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A10 GF '53 My A10 website
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Offline Fast 58 BSA

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Re: Problems mounting Hunt Mag on a10
« Reply #4 on: 21.09. 2011 15:02 »
Updated my profile now to show location.  A few years back I bought a 58 GF in what I thought was reasonable running order, then I was out riding one day when I noticed oil squirting out of the crankcase at high pressure. Turned out it had been (very poorly) welded after what must have been a catastrophic engine failure some time back. Thus, I decided to do a full teardown and right now I am collecting parts for a RGS conversion, with some special mods (among them tuned engine w/dual carb head). I will post pictures as I get underway with my project. Thanks again for the info on the mag.
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Online chaterlea25

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Re: Problems mounting Hunt Mag on a10
« Reply #5 on: 21.09. 2011 19:54 »
Hi,
It seem that the BSA magnetos were / are different to Triumph /Norton  ones etc
the body is chamfered to clear the crankcase
I posted a thread here some time ago on modifying a BTH to fit my Super Rocket
http://www.a7a10.net/forum/index.php/topic,1385.0.html

Maybe its possible to similarly modify the Joe Hunt magneto ?????????????

HTH
John O R
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Offline Fast 58 BSA

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Re: Problems mounting Hunt Mag on a10
« Reply #6 on: 21.09. 2011 22:17 »
Hi and thanks for the suggestion. I also thought about chamfering the edge where it touches the crankcase. But it doesn't look like I have enough material around the screw mount for the cap where i need to remove material. I will have to take another look

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Offline Rocket Racer

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Re: Problems mounting Hunt Mag on a10
« Reply #7 on: 14.12. 2011 07:27 »
I recently bought a joe hunt for the road rocket and was disappointed to find it wouldnt fit.
I have had to machine the crank cases to get it to fit and have now realised it carries the timing gear inboard much further than a dummy lucas one. So I will look into fitting a thicker flange plate to align the timing gear properly.
I'm also slotting the mounting flange so I can make timing adjustments without removing the timing gear.
The mag is throwing out 3.5amps so should be perfect for burning methanol.

I offered Joe up to several sets of cases and all needed mods but to a differing extent set by set.
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A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Online bsa-bill

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Re: Problems mounting Hunt Mag on a10
« Reply #8 on: 30.12. 2011 10:40 »
Quote
On Lucas magnetos some owners remove the peg from the back of the points thinking they have found a simple way of adjusting the timing, not thinking the peg is there for a reason!

On the cooking models here is no peg, the cam is turned to retard the timing, this in fact will maintain the armature to magnets position (max flux ) but points will open later in relation, the A/R unit alters the relation of the armature to the magnets, I wonder if set up for the cooking models is better although seems to me to result is much the same thing ?? my old brain runs out of cohesive thinking after a fairly short time these days so feel free to help me out *doh*
Now there is a good article in last months Real Classic by the young lady Bickerstaff (spelling) in which she describes an old magneto used on early American bikes where to retard the ignition the whole magneto is turned thereby maintaining the relation of the armature to the magnets and  ensuring best quality spark at all times.

So I'm thinking that slotting the magneto mounts will make no difference to the results of retarding ( will still move the armature in relation to the magnets when points open) however if the slots could be used to achieve retard ( rotate the whole magneto ) then best quality spark would be achieved weather in advance or retar
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All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

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Re: Problems mounting Hunt Mag on a10
« Reply #9 on: 30.12. 2011 12:16 »
You're quite right Bill, I was having a very senior moment! The critical issue is that the points open as the polarity in the armature switches which is why manual a/r units compromise spark quality because they affect the timing of the points relative to armature position. On my RGS lookalike thingy I have fitted both so that I get full spark on start up but have the advantage of being able to retard the timing slightly to avoid pinking under load.
Season's greetings!
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