Calibrating a Smith/ Speedwell Tacho

[Fanfaniracing]

Hi all

After finally setting up my engine on the Dyno, the operator told me that my Tacho is way out of calibration.

I always knew that it's not that precise...

Is there a way to calibrate these Tachos?

It's a Smith/ Speedwell Tacho IT/TCS4/12

Best Regards

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[LarryLebel]

on the back of some smiths tachs there is a potentiometer covered by a black rubber plug. turning the screw under the plug increases/decreases the range of travel of the needle. i guess this could be considered a calibration. i'm resonably sure its on rvi models but i don't know about rvc models.

[Fanfaniracing]

As Larry pointed out there is a rubber plug on the backside of the tacho.

Behind the plug there is a little white plastic screw wich i could turn to adjust to the right Rpm.

Now it works fine!

Thanks for help

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[Minigman]

Anyone know a cure for a bouncing needle?

It’s also slow to notice the engine is ticking over until some more revs come in.

Or is it just knackered?

[Polarsilver]

some just do not like electronic ignition .. may settle down using points

[abri]

In my experience these Smiths tachos are not particularly accurate even if you calibrate them. I've tried a few times. I use a timing light with a rev counter built in for reference. You set them by turning that little plastic screw at the back. They seem to be affected by temperature or something but can be up to 1000rpm off. I wouldn't fit them if you're serious about getting an rpm reading.

[Minigman]

In my experience these Smiths tachos are not particularly accurate even if you calibrate them. I've tried a few times. I use a timing light with a rev counter built in for reference. You set them by turning that little plastic screw at the back. They seem to be affected by temperature or something but can be up to 1000rpm off. I wouldn't fit them if you're serious about getting an rpm reading.

What’s the recommended tacho for electronic ignition if not Smiths?

[Fanfaniracing]

STACK is the Tacho to put in if it should be correct.

I put my Speedwell because i like it and till now it reads what the Timing gun says...

[LarryLebel]

I've had both RVI and RVC tachs on Minis and Landcrabs with Pertronix Ignitor EI and never had a problem. Currently running a magnolia tach on my S-ified Traveller with a 123 EI.

[Fanfaniracing]

On the drive this morning, i notice that the needle on my Tacho is very stable. No bumping or bouncing.

It's a RVI running on a Swiftune CSI ignition

[Minigman]

On the drive this morning, i notice that the needle on my Tacho is very stable. No bumping or bouncing.

It's a RVI running on a Swiftune CSI ignition

That’s interesting I thought only RVC ones work with electronic. I’m also running Swiftune CSI but with the RVC.