pinking gold flash

[derek taylor]

engine is pinking when you accelerate under load when it is hot i have put a fuel cat in the tank, its not made any difference it still pinks.
had a look at the points they are clean and at 12 thow plugs are L82C and look rich if anything, bike hase only done 1400 since rebuild?

[muskrat]

G'day Derek. Is it auto or manual advance? You'll need to back the timing off a degree or two. If you have manual, use it to retard a bit when it pings. If auto you can close the points a thou" or two to test it, if better reset points and re-time it.
1400 miles is just enough time to start building carbon deposits on the piston and comb chamber. This leads to hot spots and pre-ignition.
Cheers

[derek taylor]

thanx it's auto advance/retard

[muskrat]

I like timing a magie like most here like rockerbox's. If you have it set at 3/8" go back to 5/16".
The only other thing that can help is to richen the mixture, but with sooty plugs already, I wouldn't.
Cheers

[bsa-bill]

Hi Dave
Fuel cat - well there are a lot of such things around, not sure I have much faith in them and in any case your engine probably doesn't need lead additive.
However what is does need is Octane, I use Castrol valvemaster plus, it has a lead replacement but more important an Octane booster, this brings your modern fuel back to the levels of bangyness it had in the days your bike was made, £15.00 a 250 mil bottle at Halfords but you only use 1ml per litre so it will last a long time.
Sooty plugs are not always an indication of over rich mixture with today's fuel.
If this is a sudden change of running then Muskrats tips are the way to go I reckon but the Valvemaster will do no harm and might well help

[muskrat]

Good catch Bill.
 Yes raising the octane from 91 to 95 or 98 will also help.
Cheers

[Triton Thrasher]

Sooty plugs can indicate a rich idle mixture or slide cutaway, while using the wrong notch in the slide needle or a too-small main jet could still make it pink under load.

[derek taylor]

thanks lads all taken on board

[Sparky]

Derek,
If the timing/fuel tips above to not correct the problem, a possible cause of racket from the upper cylinder is a bad wrist pin bushing.  I once had one start wearing against the aluminum rod at just a 1000 or so miles after a rebuild.  Unfortunately, removing the cylinders is the only way to make that diagnosis.

[derek taylor]

right then not done anything about the pinking yet but gunna start on it tomorrow, just been reading the bible and it says tighten the unit   
 on the magneto shaft without the shaft moving. when i take it to bit's and see how it all works it will most probably all fall into place, but if not how do you hold the shaft without it all turning?

[Triton Thrasher]

Press the drive gear hard onto the magneto shaft with your thumbs, before tightening the nuts. The taper should grip it.

Doesn't always work, so check the timing afterwards..

[Brian]

Dont forget to wedge the auto advance unit in the fully advanced position when you set the timing.

[derek taylor]

thanx lads

[Ted_Flash]

I always remove the earth screw on the magneto and put a bolt in to nip the armature and hold it where I've set it, before fitting the pinion.  I think the bolt is 5/16 cycle thead

[derek taylor]

ok checked the timing, the points just part as near as dam it 5/16 btdc.
i don't think that is to far advanced?