Cota 247 Spark

[keychange]

Hi - my 247 was a bit reluctant to start on the weekend so I replaced the plug and away we went. However whenever I stopped to open a gate etc it died, which is not normal then after about 20 minutes riding I left it switched off while I explored some new tracks by foot. When I returned no sign of spark and a long push home.

I have removed flywheel, cleaned and checked everything but very very week spark. I removed kill switch and condensor from earth and measured voltage from the stator coil but it is less than .5 volts.

Can anyone tell me what the output from the stator coil should read - alternatively how many ohms in a healthy coil.

Cheers

Andrew

[b40rt]

Change the condensor before you do anything else.

[bashplate]

[keychange]

Fair enough, will do - I thought that by disconnecting it from earth it would be effectively out of the circuit and normal (unconditioned) voltage would result - the condensor is only about 3 years old although probably meant for a VW . I will seek a replacement.

[mboon]

Have you checked the points? ours had no spark at all, after a quick clean of the points (which was done through the inspection hole) she fired first kick after 5 years of not running

[keychange]

Have you checked the points? ours had no spark at all, after a quick clean of the points (which was done through the inspection hole) she fired first kick after 5 years of not running

" removed flywheel, cleaned and checked everything "

[thats_a_five]

The condenser does not change the voltage. When the points open and close, the voltage spikes and burns the points. The condenser is a capacitor and acts to absorb that spike. Capacitors have different values that absorb the spike at different rates.

Manufacturers try to match the condenser to the design of the ignition system and when they match well, the points will last a long time. If not matched, the points will burn on one contact more than the other. Fortunately there is a fairly wide range of values that will work acceptably.

The condenser is usually mounted very close to the points so the spike is absorbed faster. Some people move the condenser up to the frame which slows the timing of absorbing the spike.

Capacitors do go bad. One factor is heat. Keep it away from exhaust components. Another is internal deterioration of the capacitor from time and electrical stress. Of course like most parts, they are not enhanced by impact with rocks. I remember when cars had points and usually replacement points came with a new condenser to be replaced as a set.

Good luck with the bike.

[dadof2]

You can run the bike briefly with the condenser disconnected

I would think you should get over 20 volts ac when the bike is kicked over with plug out

[keychange]

have voltage from stator and connected that direct to ignition coil ( no condensor in circuit ) and no spark.. The coil is a motoplat maxitension red with red HT lead - single input pin. Getting 6.8 k reading from HT to earth. I am guessing there is a diode as can't get a reading from the pin to earth. Can anyone suggest a way of testing this unit?

[sparks2]

Hi

Don't set too much store by the end to end resistance values or of the coils (HT and LT) or insulation tester values.

In my experience, the coil insulation (between the internal windings) breaks down when electrically stressed (i.e. when working)

and therefore the fault is difficult to detect under static conditions.

In my opinion, the first suspect (after the condenser) should be the HT coil

and the only practical course of action is direct substitution for a known good coil.

Hope this helps.

(Of course, someone will say I am completely wrong)

(just had a duff HT coil myself).

Regards

Sparks

Edited September 9, 2013 by sparks2

[thats_a_five]

There should be resistance between the HT lead and ground and also from the single pin to ground. The resistance level will be quite different because of the wire sizes and different lengths or wire used inside the coil. There is no diode in a traditional coil.

I agree with Sparks 2 that the best way is to swap in a different coil. It does not have to be exactly the same.

With the coil disconnected, you should be able to connect your voltmeter to the low tension lead and see the points opening and closing when you kick the bike over.

[keychange]

Yes the low voltage is all good and working nicely - timing set - I did a 12 month apprenticeship on Cota 247 timing when I first got the bike.

I have dropped the coil into a mechanic in town to see if he can either test it or scrounge up a comparable spare.

[keychange]

Sorry I forgot to update this post. I bought a cheap and nasty coil about half the size of the original - goes fine. I have done some 2 hour rides without a miss

[pro sport]

Glad you got it sorted Andrew, its quite likely to be the easiest part to change , as I've found out in the past. But normally the Cota is a really reliable bike.