Longstride
Active Member
I replaced my worn old zenith with a chinese copy which has been brilliant so far. I think I might have twiddled with the mixture myself miles and miles ago and am now paying for running her rich!
Longstride
Active Member
Ok... problem solved!
So it was all caused by the pesky air mixture screw being too rich at idle! Appears to have fouled up no.4 plug and the others but mostly no.4 til she wouldn’t spark!
Anyway, today I swapped plugs, coil, leads and installed a new accuspark electronic dizzy! Engine wouldn’t start at first until I untightened clamp and gave it loads of advance, then tuned it by ear and a few test drives to find peak performance!
Runs like a dream now and mixture screw 2-3 turns out from closed. Cheers all!
So it was all caused by the pesky air mixture screw being too rich at idle! Appears to have fouled up no.4 plug and the others but mostly no.4 til she wouldn’t spark!
Anyway, today I swapped plugs, coil, leads and installed a new accuspark electronic dizzy! Engine wouldn’t start at first until I untightened clamp and gave it loads of advance, then tuned it by ear and a few test drives to find peak performance!
Runs like a dream now and mixture screw 2-3 turns out from closed. Cheers all!
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Shippers
Well-Known Member
Great to here well done to sticking with it and working through it...electronic dizzy are v.good I pxxxxd around with running probs on my 101 till I realised it had done only 14k kilometers on a 24V dizzy and had been fitted with a 12V from a P6B God knows how many miles that had done... after wasting money buying a module that didn't fit...sparkright sorted it...
@Longstride - you mentioned taping a flaky vacuum hose earlier in the fred .... might be a good idea to replace that before the tape lets go 
Longstride
Active Member
Oh and yes I replaced the vacuum advance pipe with a new one too £3.99
£3.99
Longstride
Active Member
One question though! I’ve got her running well, plenty of power with how I’ve set timing.
Is it worth putting a light gun on and FINE tuning it or will I get no real benefit. I’d say she’s as punchy as she was! Even slightly accelerates uphill in 4th!!!!
Is it worth putting a light gun on and FINE tuning it or will I get no real benefit. I’d say she’s as punchy as she was! Even slightly accelerates uphill in 4th!!!!
Longstride
Active Member
Setting your carb by ear is pretty good and easy enough to do. You generally only have an idle mixture screw so you won't affect mixture at higher revs
Set your revs low, then turn your mixture screw in until it starts to run badly.
Now turn the mixture screw back out again until it runs nice and even again, then give it another half turn.
Set the idle and you should be good to go
Set your revs low, then turn your mixture screw in until it starts to run badly.
Now turn the mixture screw back out again until it runs nice and even again, then give it another half turn.
Set the idle and you should be good to go
Longstride
Active Member
Cool thanks! That’s exactly what I’ve done so fingers crossed! The six turns of idle richness caused this whole thread anyway!
Colthebrummie
Well-Known Member
Colour tune is a little device you screw into the spark plug hole and it gives you a window into the combustion chamber. When the engine is running, you can see the detonation as the spark ignites the fuel. You then tweak the mixture screw until the correct colour of the bang is produced. I had one in the seventies but you had to use it in low light conditions to really see what what going on. I don't know if they are any better now, I haven't seen one for years
Col
Longstride
Active Member
Cheers all! I guess even though running her rich at idle I was burning some of the crud off running down motorways etc, but these last few months I’ve just been idling about an estate deer watching so it’s built up loads of crap!
I’ll pull new plugs and check for colour soon but I might invest in one of these magical colourtunes for a giggle!
I’ll pull new plugs and check for colour soon but I might invest in one of these magical colourtunes for a giggle!
