It‘s official - she hates me! She wants to be a garage queen, but I will force her to like me one day. I was having a lovely late afternoon ride, and then it happened on the way home... Accelerating through the gears coming out of a village, and suddenly she started backfiring and missing very badly...

First thing I would check is if there is something draining current. If it’s negative earth, disconnect the positive lead from the battery and place a digital multimeter between battery positive and the lead you just disconnected. Set the multimeter to measure current or Amps. First with ign off, th...

John, I don‘t know if anyone ever made a spacer, but the suggestion above would also be what I would try. I had a similar problem with my original head which had been skimmed so much by the PO, that I didn‘t have enough valve clearances. Even if I did, I would probably have too much compression, whi...

Dear Simes,
I think you‘ve got it. Turned the pilot screw out 1/2 turn and she ran much better. All the hesitation and misfires are now gone and she ran beautifully. Very happy. Thanks again for all the help from everyone.
Cheers,
Gui

I'm not aware of the Thorspark device - does in keep the points, capacitor & bobweights? - or are they binned for Hall effect pick-up & electro mapped adv/ret? Cheers, John John, thanks for the help. Hopefully I answered the rest of the questions in the previous post. As for the Thorspark i...

Happy to report that after a longer run today, she is running much better without the misfires (almost...). But going back to some of the questions above. The Square four, although still in the run in stages, was running very well before. Last year she did about 200 miles, but at the start of this y...

Hi John, All is possible, but I 'm reasonably sure the electrics are in good order. The wire harness is new, and I triple checked everything during the rebuild - all connections, good ground, etc. I'm using a Thorspark electronic ignition with a new coil and converted to a 12V system with an alterna...

I don't have a boot on the distributor, but I do have a copper washer on the rocker box inlet. I just checked the distributor and all the HT pots, and everything was clean and dry.

Well, managed to do a short ride today, and I'm happy to report that the problem seems to be solved. The Square 4 ran smoothly so the cause was apparently indeed the partly blocked mesh on the petrol tap. I didn't try a high speed run, as I 'm still bedding her in, therefore can't say how the power ...

Hi Peoples, - the comments string seems convinced the issue is fuel flow - so a few thoughts; - whilst faffing around with the "plumbing" 1/ Have you checked that the tank is able to breathe? - I have not had the problem specifically on my Square; - but I recall a Tiger Cub from longtime ...