Small block 1992 750S cylinder drops out

Hi, I have a frustrating problem which I can’t seem to cure. Sometimes when I start the bike, the RH cylinder is running with an intermittent, weak spark, BUT if I pull off the HT cap off that plug and then ‘place’ it back on…not the usual push fit ( it’s more like resting the cap on top of the plug) it runs great!!

I have done the methodical, replace plug, cap, lead and coil and it’s still doing it, does anyone have any ideas or thoughts?

I have Rita ignition, and with the new coil get a good shock/ spark from the cap…but still won’t fire!


The ONLY thing I can think of is wrong plug cap or leaking valve, but if it works with cap resting on the top it suggests to me the need for a resitored plug or plug top, I am guessing here. Have you spoken to the RiTa guru?


Thinking a bit and

Years ago i had a Norton do similar it was traced to a faulty condensor in the ign cct no idea if the rita has condensors the points sure do.

There was also Annies Suzuki 125 that faultered in the damp a spark track you could ONLY see in the dark of the garage the plug top was tracking the spark away THAT one caused a few disturbing moments.guzzibear2014-01-31 12:20:52

Mmmm tried several caps, new and old, new and old plugs, with the new coil If I pull off the cap I get a serious shock…my thoughts now are timing and it’s sparking at the wrong time?..

the Rita guru sounds good…could I ask who he is or how to contact him?


Make sure the plug thread in the cylinder is clean and you don’t have a whisker on it shoring out the spark.


Not with Rita.

DO NOT PULL PLUG CAPS OFF WHEN RUNNING IF IT’S ELECTRONIC IGNITION You risk destroying the coils’ switching transistor. Depends how good the back EMF pulse protection circuitry is if it’s even got any Anyway as Rita fires both plugs at once it could be that the problem is actually with the LH side, and HT Voltage is too low. Only getting sparks by adding a gap into the HT lead (i.e. removing cap and replacing) is a classic sign of low HT Voltage, I think, adding an extra gap forces the Voltage to increase, THEN it makes a decent spark. Appendix: is new coil correct for this Rita kit - apparently there are two output variations, 2 x 6V coils in series, or, 2 x 12V coils in parallel and separated by diodes.
Mike H2014-01-31 15:16:23

Rita guru

This is true, you used to be able to get a gizmo that sat in each plug line to “increase” the spark. It was actually just a spark gap.

Ok, that sounds good. I have diodes so a call to AO services would seem the next step. The bike is much modified and the amp is placed in such a position that it has been getting wet!

Would you believe/remember an old tune up kit for british 2 strokes was a shirt button!

Ah coils in parallel then. Maybe a case of coils have to be a matched pair (one new and one old isn’t compatible) or diode(s) on its (their) way out. Maybe you need to treat the LH side same as you did for the RH side so everything is more balanced?

Spoken to the guru and the Rita/ Amp is not the problem. As already suggested it would seem best to go for a pair of new 6v coils in series and junk the diodes/ 12v coils in parallel. This should be a better set up anyway and iron out the potential problem that I have…fingers crossed.

Did he suggest that? I thought the 2x12v coils were fitted to a different type of Rita, and they were not interchangable. ie. you couldn’t fit the 2x6v coils to a box designed for 2x12v.

No will be OK. The amp is identical for either configuration I believe. In fact should be better as the switching current is halved so easier for the amp. So also better for the bike’s battery and charging system too. I concur with the guru… 'Fact never saw the point of the parallel set-up, looks too much like a bit of a bodge to me.
Mike H2014-02-01 18:24:06

Al Osbourn is a good man, you can trust him. Not saying you can’t trust Mike of course.

Triumph Bonneville 140e model came from the factory with Lucas rita and 6v coils connected in series


I’d be guided by whatever Alan O says. Our local “Rita” Guru, he can sort just about any gremlin. His “bench test” method is to fit the component to his own bike and ride it around!

Genius Love that idea.