Hello & help please

[Classic-dude]

Hello,
I have an HA 1056 viva & I've recently had the head converted to unleaded. I've changed a couple of carbs, put a electronic ignition and a new coil but still have a misfireing issue. Can anyone help as its so frustrating as I want to use it everyday. It keeps backfiring on though the carb. I'm willing to ring anyone who could give me some idea on how to fix it
Many thanks
Phil

[Bob perry]

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

[Classic-dude]

Hi Bob,
Thanks for that, I'm going to give it a try tomorrow. Fingers crossed it works

[Bob perry]

Another thought just occurred.
When they converted the head to take unleaded, did they machine the head face as well? Just wondered if they had, would it have lowered the compression a bit, and maybe need a different head gasket?
Probably not, but just a thought!

Mine has never been converted, and runs quite happily on unleaded. I'm not sure it really makes so much difference anyway unless you are doing thousands of miles a year. The seats are probably pretty hardened after 50 years anyway!

Good luck tomorrow.

[vivapete3]

Hi Phil and welcome to our club, I have 3 HC 1256CC VIVA's have had a slight misfire which I tried to cure with accuspark electronic ignition system, could'nt even get it started with electronic ignition, so reverted back to points etc, and not perfect but runnable still looking for a electronic system which suits Vivas , hope this might be of use , I think the other reply is a possible solution the distributor gear slightly out of sync, good luck, vivapete3

[GAV]

Hello,
I have an HA 1056 viva & I've recently had the head converted to unleaded. I've changed a couple of carbs, put a electronic ignition and a new coil but still have a misfireing issue. Can anyone help as its so frustrating as I want to use it everyday. It keeps backfiring on though the carb. I'm willing to ring anyone who could give me some idea on how to fix it
Many thanks
Phil

Hi Phil, if you fit electronic ignition straight into the existing Dizzy, as set at TDC for the points, it can have the effect of retarding the ignition timing and moving the Distributor gently might solve the issue. Just a thought.