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Carby Backfire and Valve timing - Need Help!

Not_An_Abba_Fan

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I vote it's the timing out as well. Follow the above instructions and see where you are at.
 

bogan_vk

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significant vac leaks can cause back firing and flames from the carb.

personally i check for number 1 TDC by taking off the rocker cover. the harmonic balancer and piston goes around twice for each cycle (once on power, once on induction) so even sticking a screwdriver in the hole you still have a 50% chance of getting it wrong. not to mention you have just stuck a screw driver in your engine. the thought of that makes me shudder.

with the rocker cover off you can watch the #1 intake valve close which means you are on the correct stroke. and sticking a bit of thin wire in the spark plug hole is less likely to damage anything.

once you are sure the intake valve has just closed and you are on top dead with your piece of wire, the mark on your harmonic balancer should be lined up with the 0 mark on your timing cover. if not your blanacer has spun or your cam timing is out.

so lets say the balancer lines up with your piece of wire and the timing mark, and your intake valve has just closed. you can safely guess your at #1TDC. move to your dizzy. pop off the cap and look where the rotor button is pointed. you can proceed in 2 ways.
1. switch all your leads to suit where the rotor button is pointed
2. undo the retaining bolt, lift the dizzy about 4 inches and rotate the rotor button to suit your cap.

either way works fine, but switching your leads may mean the shorter ones cant reach your sparkplugs.

drop the cap back on, tighten everything back up and fire her up.

dont forget to check that your rotor button is going CLOCK WISE. and your firing order is [insert correct firing order here]
do this^^^^^^ ....its a bit better than my dodgy method of 50/50 chance and a screwdriver ,even though my method works for me eventually.
 

oscar03

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i have seen symptoms like these before and all it was, was the HT leads where in the right order only backwards have you double checked them?
 

oshi16

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Thanks Ari666! That's some great advice! And thanks Bogan and Not an Abba Fan for your inputs (p.s. love your display pic fan).

But I have a query; if I took of the oil cap and shined a light down it, do you think I'd be able to see the valves clear enough? Probably a dumb question, because I'm going to try it anyway. This is not because I don't want to take off the rocker cover, it's just a time measure. If it fails Rocker cover for the win!

Thanks a bunch guys!

Brendan
 

oshi16

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Hey Oscar! What are the HT leads? do you mean the ignion leads? if so I had them around the wrong way at first and then corrected them. I'm sure of that!

Thanks for the input =)
 

Guzzoline addict

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Just take the number 1 sparkplug out and stuff a rag in the hole. Crank it over (with coil lead off) and soon as it pops, stop and crank the motor backwards buy hand to the timing mark.
 

Not_An_Abba_Fan

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HT lead = High Tension lead. Another name for ignition leads.

Guz addict, that won't work if the harmonic balance has spun on the rubber.

I would double check you firing order, 1 5 3 6 2 4, clockwise. When looking at it from the front, number one is to the left of the vacuum advance diaphram, with the diaphram on the front of the dizzy and the rod parallel with the block.
 

oshi16

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Also, Yeah I figured HT were the Ignition leads, just didn't know what the HT stood for. Cheers!
 

strgas

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easy way to check for #1 tdc is set the timing mark to tdc on the balancer remove number one plug place a length of hose onto the plug seat and blow into the hose and see if it holds pressure or just blows thru , once on tdc firing it should hold pressure and not blow thru , Question is why did the rocker bridge break in the first place ? bent valve or gummed up lifter ? bent pushrod any marks in the top of the pistons from valve contact , is your cam shaft turning ? fibre gear or alloy gear fitted to your camshaft ? does the dizzy turn when cranked over .
 
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