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Chinese digital rev counter

Submitted by george_phillips on Wed, 10/10/2018
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Electrical

I bought and fitted a Chinese rev counter. It works by sensing the spark lead impulse via a cable wrapped round the lead. It is set correctly (4 stroke single) but seems to read about double what I consider the revs to be. It's as if there's a spark on the exhaust stroke. It does back fire on the overrun but that may not be related. Any one got any clues as to what's going on?

George

Submitted by dan_field on Wed, 10/10/2018

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Im assuming this is on your single George? If itâs not and you have electronic ignition the wasted spark would do that, other wise joking aside try switching between the two settings and see if it makes any difference. It might be stuck on 2 strike? And by way of a check what does it read at slow tick over?

Submitted by george_phillips on Wed, 10/10/2018

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I have an idea I tried the two stroke setting Ian. In theory that should double it up again but I can't remember. But I'll give it another go.Yes, it's the ES2, Dan. I'll check the tick-over reading. I was really after a cause rather than (at this stage) a solution.

George

Submitted by mikael_ridderstad on Wed, 10/10/2018

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Do you have a Lucas magneto?

I had initially some trouble with a Scitzu rev counter on my Honda twin racer. Scitzu is a popular rev counter on classic racers. Length of cable tyrapped along the ignition lead is critical. Also direction of the pickup lead matters. So I think that number of turns you have can affect. On the Honda, I had to move the sensing lead far away from the ignition coil to get reliable reading. Some experiments might solve your problem.

Submitted by myrry_wilson on Thu, 11/10/2018

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My mate had exactly the same problem with one fitted to his HRD 350, with long stroke JAP engine. In top gear my ears were telling me about 1500 rpm @ 35 mph, the rev counter said 3200! He has cured it, I will find out what he did and report back later today.

Cheers

Phil

Submitted by george_phillips on Thu, 11/10/2018

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In answer to Dan's query (slow tick-over reading) it hops about all over the place; 720, 1440 then 2000+ then back to 1440. I reckon it was plodding away at around 360 (15 exhaust pulses in 5 seconds) so nowhere near correct. I've lost the installation instructions now but I recall giving it few more twists round the HT lead after initial installation owing to the inaccurate reading. The annoying thing is sometimes it's about right - when it decides to stabilise. Looking forward to hearing Myrry's solution today.

Submitted by myrry_wilson on Thu, 11/10/2018

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Sorry George I am afraid It appears Bill hasn't cured the problem, I thought he had, since I last rode it 3 weeks ago. His reply to me is below. (Not that it's much use of course.)

From Bill,

Mine is a Searon back-lit digital Tach Hour meter, waterproof, for 2/4 stroke engines, about £20 on eBay.

It did not function very well, reading slow and intermittantly. I have put another couple of turns of the sensing wire round the high tension lead and re-programmed it for 1 pulse every 2 revs (my magneto runs at half engine speed). I thought I had done this initially, but when I checked, it was setat 1pulse per rev, its default position. I have not run the engine since, but not holding my breath. Like much Chinese stuff, I suspect its default position is 'faulty'.

This has become a challenge to find the answer!

Myrry

 


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