The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: BSA500 on 23.06. 2025 13:45
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Hi,
I would like at sometime in the future fit a rev counter to the a7 via the oil pump drive, its been a dream of mine. I know I have to get the inner timing cover which do come up for around £100 which is ok. But the rev counter head is alot of cash. I dont mind using the replica ones but has anyone seen a 3:1 produced by any of these companies.
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i used a 2 to 1 magnetic rev counter and had the internals sorted to make it 3 to 1 . a long time ago now , if you want a chrono 3 to 1 be prepared for a price shock.
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I've already seen some of the prices *eek*. That's why I considered the replicas but I've not seen any 3:1s
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Can't you get a standard Chrono speedo recalibrated and use that?
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Not so sure purchase price plus cost of someone to do the work these days would be much cheaper???
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How about converting 2:1/4:1 to 3:1??
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Hi All,
Find an old speedo and have it converted to a rev counter would be the most economical way to go in my opinion?
One with an "L" in the number would simplify the modification as the rev counter are opposite cable rotation ,
The speed mechanism is separate to the odometer.
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John
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Give Russell a call at Chromometrics
http://www.chronometrics.co.uk/
+44 115 9206156
Try a 0 instead of the +44 as I’m in US
He has them off the shelf as well as refurb supplied ones.
You’re in UK so won’t have to worry about postage being so high!
I purchase a Tacho as well as restored and converted my speedo I sent out to him.
Don’t know what the prices are today as I got them back in 2016 😳 time flies
Treat yourself
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Thanks for all the answers the best way to go is it seems, grab a second hand speedo and convert, or convert a magnetic. Doesn't look like the replicas come in a 3;1 ratio any where I've looked. You never know I might wander round a boot fair and see a rc1303 for a fiver *smile*
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Just looking at the grey face A65 tacho. Those are 3:1 ratio and clockwise rotation would these not just go straight on without any modifications ?
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BSA500 the magnetics i have are 4to1 and 2to1 the 2to1 was converted to 3to1 for betsy beeza, never seen a magnetic 3to1 where are they? aha found them , but are they clock wise drive or anti clock without taking mine off i can't remember but think its anti clock from the oil pump , someone with a super rocket will know.
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Try Ashley Pople
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i couldn't resist taking the cable off mine driven from the oil pump and it is anti clockwise , you need to check these A65 ones
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so to understand this the cable drives anti clock but the needle on the dial moves clock wise. Yep that makes perfect sense to make them work like that *conf*
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the bsa a10 oil pump drive runs the cable anti clock so the rev counter i had done was made with an anti clock dial and gearing .
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Stumbled across a forum post on here from God knows when that stated the A65 rev counter/oil pump drives clock wise so A65 clocks would need converting but they are a dam sight cheaper than the chronos. A black face rev counter can be had for £60 that's 3:1 ratio.
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Does anyone know if the RSM3003 black faced tachos used on later A65 can be used as is on the drive from the oil pump drive from our pre units??
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our pre units are 3 to 1 anti clock from the oil pump drive
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If the A65 clock is magnetic ( cable entry in centre of the case) then I wouldn't think it could be converted (rotation) without changing the entire mech as the needle is move by proximity to a magnet spinning on the end of the cable axis.
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yes correct bsareg and the magnetics internals get changed from 2to1 or 4 to1 to 3to1 anti clock like i have had done on betsy donkys years ago and betsy two last month , gaggs did betsy 1's and the nice chap at timeless motorcycles did betsy 2's