Gunson's Tachostrobe

John Roberts

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Borrowed one to do the timing on my '82 RS, but it doesn't have any instructions with it. I've Googled and done a search on the Airheads section and there's nothing of use on the Gunson's site.

The model is the black one (different models have different colours apparently) with a knurled wheel at the back that moves a pointer along 3 scales marked in rpm. On the other side there is a protruding plastic screwhead which looks like a setting adjustment, on the other side there is a clear plastic prism. There are +ve and -ve leads provided to power it from the bike's battery and there is a lead that clamps on to the plug lead.

Anybody?
 
nick.ct said:
This is a different model than yours?

http://www.gunson.co.uk/items/pdf/Products/77008_Instructions.pdf
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Yes, that's a different one, thank you anyway. Mine doesn't have a model number or identification other than its name- Gunson's Tachostrobe. It lights up the flywheel marks (fuzzily) and confirms that the advance works correctly and perhaps that's all there is to it, it's just that there are three things on it that I don't understand.
  • There is a clear plastic prism on its side which lights up when it is working, the image of a black line wanders up and down this for no apparent reason.
  • The knurled wheel at the back with a pointer running up and down the rpm scales, turning this wheel seems to have no effect.
  • The adjusting screw sticking out of its side, I haven't touched that.
I am confused. And bemused.
 
Result!

I had borrowed the strobe from the BMW Club but was reluctant to bother the gentleman in charge of the Tool Hire Section on a Bank Holiday weekend, he does the job for free after all, and he does it very well. Here is his reply, he only took 18 minutes to respond!! I am passing this on for the benefit of others who have the same problem with this gun, it should come up if someone does a search for Gunson's Tachostrobe in the future. It also shows the reason why I joined the BMW Club, i.e. access to all the special tools that it has available. :thumb2

*************************************​

Hi John,

No problem, with answering queries.

Please see my responses in blue text.

Did you use the static ignition box, or go straight to using the strobe?

Regards

M ----

--------------------------------------------------------------------------------
From: John Roberts [mailto:xxxxx@xxxxx]
Sent: 08 April 2012 10:30
To: M. ----
Subject: Timing light

Oh dear, I do feel stupid, but here goes:

I've had a look on the Gunson's website and then wrote the following appeal for operating instructions on the Airheads section of UKGSer, they usually come up with the goods, but not this time it seems:

Gunson's Tachostrobe
... It lights up the flywheel marks and confirms that the advance works correctly and perhaps that's all there is to it, it's just that there are three things on it that I don't understand:
That's about it really. Do you get a good range of movement from nil advance to full?

There is a clear plastic prism on its side which lights up when it is working, the image of a black line wanders up and down this for no apparent reason.
That's an RPM indicator, so you can set the RPM at which you want to test the ignition system. You set the speed by the big thumbwheel, and when you turn the strobe on, the black marker line shows when the engine revs are equal to the setting on the strobe. The function is for vehicles which don't have a rev counter (or it's suspect), so you shouldn't need to use it.

The knurled wheel at the back with a pointer running up and down the rpm scales, turning this wheel seems to have no effect.
Used in conjunction with the prism as described above.

The adjusting screw sticking out of its side, I haven't touched that.
That's for setting the sensitivity of the inductive pickup. Some vehicles' ignition systems give weaker sparks than others. If you are getting a light then all is o.k.​
I certainly don't expect a response on a Bank Holiday- running the tools section is a service you provide free, for which I am extremely grateful and appreciative- but by asking via email it gives you the choice of when to reply. For my part I do have other things to do on the bike, so no hurry.

Regards,
John
*******************************************************​

So, job done. It really was as simple as it seemed, deceptively simple. And a heads up for the benefits of BMW Club membership.
 
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Kenny said:
John,

I think most of us already knew that and felt embarrassed for you :thumb
Top reply from the BMW club member :thumb2

Thanaks for posting this...I may even acquire one myself :bounce1
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Fair enough, but I REALLY would have liked it if one of you had said so. As I said in my second post:
It lights up the flywheel marks (fuzzily) and confirms that the advance works correctly and perhaps that's all there is to it,
I've never used a strobe before, perhaps there's another dumbo on here who hasn't either. He shouldn't have any doubts as to how to use it now. :beerjug:
 
John Roberts said:
Fair enough, but I REALLY would have liked it if one of you had said so. As I said in my second post:
It lights up the flywheel marks (fuzzily) and confirms that the advance works correctly and perhaps that's all there is to it,
I've never used a strobe before, perhaps there's another dumbo on here who hasn't either. He shouldn't have any doubts as to how to use it now. :beerjug:
Click to expand...

An old thread, I know, but I also have an identical Gunson Tachostrobe and whilst I have owned it for over thirty years, I've never used it before. Having had the heads of my R100GS-PD twin plugged, Jim Cray recommends that the ignition timing is slightly retarded. So I dug out the old timing light and dusted it off. Then connected the + and - clips to the battery terminals, and removed the LH plug lead, attached the loose fitting spirally thing with the plug lead attached to the end of it. Started the engine but no light emitting. Maybe it's died of old age. Other than the knurled wheel at the end, there seems to be no other adjustments. Puzzle.
 
Right, well I got it working. The conical spring thing needed shortening by an inch so it actually gripped on top of the spark plug. So I started to try to adjust the timing but as I'd altered the throttle and mixture settings back to the recommended base setting, she won't tick over any more. :blast I'm going to leave things until tomorrow as at present I can neither adjust the timing nor the carbs with my new gauges. The marking on the flywheel appears to be the letters 'OP' with a white blob beneath it, and not the 'Z' as shown in Haynes.:confused:
 
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