Author Topic: A10 timing gears A7 Longstroke timing gears mixup (solved)  (Read 944 times)

beezermacc

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I was round at a mate's house at the weekend. He'd just rebuilt his A10 engine. Whilst doing so he'd changed a couple of the timing gears for ones in better condition. Mistake! In spite of everybody's best efforts the bike wouldn't start. A few pops in the exhaust was the best result. After a bit of head scratching we decided to put the original gears back as this was the only significant change made during the rebuild. Hey presto! the bike strted second kick and sounded fine. Having some knowledge of A7 longstrokes I was aware that the gears are different but didn't think my mate had any A7LS bits in his collection. I though it worthwhile to do some pictures. If I'm building an engine I always check the timing gears. Here's the pics, they're on the Tech tips page of our club website http://www.cheshirebsa.co.uk/

Online bikerjohndavies

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Yep, the timing marks are a different number of teeth apart. The long stroke A7 is 16 teeth between the crank shaft pinion mark and the cam shaft one whilst the later short stroke A7 and A10 one is 20.
1937 Panther M100 Rigid, 1946 Ariel Square 4, 1952 Norton Model 7, 1953 BSA A10SF (WIP), 1954 Ariel VH, 1961 Triumph T120R

beezermacc

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Yep, the timing marks are a different number of teeth apart. The long stroke A7 is 16 teeth between the crank shaft pinion mark and the cam shaft one whilst the later short stroke A7 and A10 one is 20.
....all the gears are different actually!

Online berger

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can anyone or lots of you tell me if the timing gears on a bsa pre unit have a different pitch, land , and angle compared to pre- unit triumph gears.  I think they do but not sure , cheers

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anyone? *sad*

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G'day berger.
I had a look around the net but can't find an answer.
I did find a handy pdf from the BSA owners club showing the different timing marks.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Muskys Plunger A7

Offline ironhead

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G'day Berger,  fairly sure there both the same.  16 DP , 14.5 PA.  Soon I'll be Overhauling a pre-unit triumph engine & will check for sure.
SA

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cheers musky so did I before posting. I need a geezer who has a  pre unit triumph timing cog to compare with a beeza cog regarding them meshing correctly or not compatible *dunno* I have a bit of a disagreement *fight* *fight*

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ok ironhead I am all ears for then. I think the pitch and angle are different, I will have to accept defeat if I am wrong and go in the corner facing the wall *pull hair out*

Offline Swarfcut

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bergs, Any online seller will list any possible application for these gears, so worth a look. Works with clutch plates, amazing (not) that some plates fit  some BSA late models and early Triumphs.

 What's the problem with sourcing the right parts, or is it that you have a stash of gears looking for an engine? Found these in an idle moment, goodness knows what they fit.

https://www.ebay.co.uk/itm/Triumph-Timing-Gears-1-Lightweight/254715963483?hash=item3b4e41285b:g:PVAAAOSw3NBfUmZK

 These look kinda weird, I reckon you're on a looser trying to find something to fit.

 Swarfy.

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yes swarfy geared up and nowhere to go *pull hair out* *bash*

Offline Swarfcut

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   For the benefit of those folks following berg's problem, turns out the gear in question is the fibre magneto drive gear, not the whole gear train. He's gotten an  ATD that won't mesh with the BSA cam gear.  Turns out the rogue ATD is from a Triumph, with 50 teeth, not the correct 44.

 Took it on myself to send a personal message, and with a bit of detective work looks to be sorted.

 Time for bergs to celebrate in the usual way?

 Swarfy.

 

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I will drink to that -------- later *beer*