The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: A10Boy on 09.05. 2010 19:44
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I have a smiths speedo type SC 3304/11 followed by 1692 fitted on my A10.
I know its not correct for an A7/A10, can tell me what it's off ? That would be a great help.
Cheers
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Hello Andy!
That would be:
1960-1963 Triumph 3TA Twenty One
1960-1963 Triumph 5TA Speed Twin
1960-1962 Triumph T100/A Tiger 100
Cheers, Markus
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Cheers Markus *smile*
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It now on fleabay if anyone's interested.
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Would it fit on a 1954 Golden Flash?
Do you have an idea what is 1440 ratio? 1500 ratio?
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First, I see that you have discreetly joined the forum and I will respect that by discreetly saying:
WELCOME TO THE FORUM, ZIV. TELL US A LITTLE ABOUT YOURSELF AND YOUR BIKE! *welcome*
Now, about that speedometer, it's a great question. I did my best to figure this out for my own speedo, and my attempt is described at http://www.a7a10.net/forum/index.php?topic=701.msg4399#msg4399.
Richard L.
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Richard,
I have two BSA's. 1969 A65T (Thunderbolt) that I completely restored about 7 years ago.
Currently, I am in the process of restoring a 1954 A10 (Golden Flash). I am looking for a speedometer, and in that search
I was asked about the ratio (1440 or 1500) as well as the Smith's part number. I was able to find out the ratio between
the speedometer driving gear to driven gear (6:11 teeth per inch), and even with a phd in mathematics, I could not relate
the tow ratios!
Thank you very much for the information you sent me as finally I understand the meaning of those ratios as well as the
relations of the gear ratio to the "1440" number...........
Regards, Ziv
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Ziv, There's a thread (or some)on here somewhere, where that has been discussed in depth...I'm not 100% certain but think 1490 is what plungers run, but should be same for swingarm jobbies too. ...I have a 1620 and it reads about 11% under
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Thanks for the information. Richard sent me information that explains how all these relate to each other. It has to do with the ratio between the speedometer driving ratio and the driven gear, the wheel radius and the wheel revolutions per odometer mile.
BSA has quite a few different "ratios". It looks to me that your ratio should have been 1440 and this is why with a 1620 ratio you have about 11.11% difference ...........
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Hi Andy, over in NZ there is a guy who will take pretty much any smiths speedo and make it into an a10 one, he changes the ratio when required as he reckons that is simple and even asks you to check he's got it right with a gps if you want, he will fit the right face eg with the correct part number if you supply it otherwise he fits faces with no number. He can also change the trip config (side/bottom) when needed albeit he has trouble getting the parts to do that.
He can also "convert" speedos into rev counters but thats about $400 exchange.
So cos of the way things are ovver here I would have kept your "wrong" speedo and got it changed as any chronometric speeo fetches lots of dollars over here....and its vey unlikely the correct one will turn up anyway.
Is modifying what you have an option where you are?
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Well said Kiwi.Can't be fussy with Chronos. Be happy you have one.
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BSA has quite a few different "ratios". It looks to me that your ratio should have been 1440 and this is why with a 1620 ratio you have about 11.11% difference ...........
Thanks Ziv, I figured that out a while ago fairly much same calculation as Richards, before I put the bike back on the road so I'd know in advance. I've also fitted a digital bicycle speedo (which somehow went to the default calibration 203cm instead of 213cm, so caused my a speed fine!!!), and since then also a bicycle GPS speedo, and recalibrated the digital one.......they all now co-relate nicely with my ~11% 'errror'....
...I also had a digital one on the MotoG, but spilled brake fluid on it when changing the handle bar, and it dissolved *eek* which prompted buying the GPS one (by chance the same day the overdue speed photo arrived in the mail= but that's another story). Handy thing about it is I can use it easily with whatever bike/vehicle.....no calibration required *smile*
So long as I know the 'error', and the speed zones which are in miles anyway, I can just get used to it- Or just look at the GPS in (speedo in tank is not always convenient anyway)