by Bob perry » Sun Nov 27, 2016 5:56 pm
Hi Phil, I had similar backfiring problems with my HA SL, after an engine rebuild, and I know how it can drive you mad!!
You say you have changed carbs! are they PSE1.4 or 1.6 ( different jet settings, and with or without economy units).
The incorrect ones will give you similar problems if the wrong ones are fitted
I eventually stripped out the carbs and cleaned all the jets and changed the diaphragms.
Still backfiring, which was a bind!! Tried electronic, still the same.
Re-fitted new points and condenser, and changed the leads and plugs .Better but still missing.
Had to be timing. Used a timing light, but couldn't get it to line up with the tag on the pulley, miles out!!!
Took the dizzy out to check the drive gear position. The offset didn't look to be in the correct 90 degree to the block position on No1, which meant the dizzy was never able to be in the right place, as the advance/retard fouled the block.
Took the plunge and removed the engine. Sump off and re-aligned the oil pump drive, by one gear, so that the dizzy drive came in to the right place.
Re-fitted engine and fired her up!!! Success. Stupid boy Pike!! Note to self check before fitting next time, if there is one!!!!
Luckily, I also managed to get hold of an, almost new, carb from a Club Member, which proved a great benefit, and she runs lovely now!
Not saying though that you have the same dizzy cog line up problem that I had, but it certainly sounds like a timing problem, if the carbs and jets and the ignition side are ok.
Hope that helps. Good luck.
Bob
Mona Viva