Pinging thoughts

[Triton Thrasher]

I lifted the needle 2 notches and went up 1 (135 to 140) on mains,

Are we taking about Amal carb/carbs?

Don't want to sound cheeky, but that looks like a haphazard approach to carburettor tuning.  Can't you get the main jet correct at full throttle, then turn your attention to the needle?  If you're doing 95mph, the main jet had better not be too small, or a seizure (or holed piston) might be the first symptom you get.

A notch on the needle is quite a big adjustment.  A change of two notches can take it from too weak to too rich at mid-throttle.

[muskrat]

G'day TT,
             2 X 30mm Kehin PWK flat slides. Just went back to original settings. The needles in these things come in a multitude of sizes, long, short, thick,thin, long or short tapper. Each for a different part of the throttle opening. Once I get the head back on I'll try a colour tune and start playing with the needles.
I can see on the piston and combustion chamber where "the mice have been at it", tiny little pock marks from the pinging.
Cheers
             

[Triton Thrasher]

G'day TT,
             2 X 30mm Kehin PWK flat slides. Just went back to original settings. The needles in these things come in a multitude of sizes, long, short, thick,thin, long or short tapper. Each for a different part of the throttle opening. Once I get the head back on I'll try a colour tune and start playing with the needles.
I can see on the piston and combustion chamber where "the mice have been at it", tiny little pock marks from the pinging.
Cheers
             

At the end of the day, that's probably a better carb than an Amal.

The dynamometer suggestions sound sensible!

[muskrat]

The settings I had before I went back to original weren't too bad by plug colour but sluggish due to the retardation to stop the pinging. So will have to look at needles that richen low to mid throttle settings, maybe thinner and longer taper. Once I nail it they will not wear or distort like the A(ni)mals.
Cheers

[chaterlea25]

HI Muskrat,
I have heard that there are a miriad of different brews of "petrol" downunder and that it is very variable,
From experience with a couple of drag racing gixers a few years ago I know that if avgas is added to increase the octane rating it affects the flowrate through the jets, ie increasing the octane leans the mixture
What are you adding to increase the octane?
I dont know if "proboost" or similar have the same effect??

Cheers
John O R

[muskrat]

G'day John OR,
                    I use Nulon pro strength octane booster at a rate of 8ml per lt and caster oil 500/1 in 98 always from the same servo (caltex). Can't use ethanol blend with fibreglass tank.
Cheers

[muskrat]

Update, Head back on running 98 (no additives) 30 deg adv. Colour tune says lean at 1/4 throttle, good at idle. On the road very rich at 1/2 and above. Pinging starts after about 5 minutes running so is related to 1/4 throttle. So either thinner needle or richer slide needed. 2 carbs cost $250, 2 slides cost $220, ouch ! Try needles first as both cover this region.
Cheers

[Triton Thrasher]

Slides can be altered weaker bt filing the cutaway, as you probably know.

You can alter them richer, at least experimentally, by supergluing slivers of cork to the edge of the cutaway. Might be better than spending thousands on slides that don't work out.

[muskrat]

Good idea with cork on cutaway TT, not sure if possible. Going down now to lift needles further but thats going to make 3/4 too rich so will have to go smaller taper angle. Needles are $20 each. I know it would be easier to go back to A(ni)mals, but I like a challenge.
Thanks all for your input.
Cheers

[muskrat]

PS might have to moove this to carb section !

[muskrat]

Getting closer. went for a richer pilot from 38 up to 45 !! A bit fluffy at idle good acceleration to 1/2 and rich at 3/4 but good on mains. Just a slight hint of ping after a good flogging. Ordered needles from the US.
Saw 100MPH today at 6000rpm felt great.
Cheers

[terryk]

I have heard that you can use acetone (however you spell it) to boost your octane level. Im not sure how much to put in but I will try and do a search about it. My mate runs a bit of it in his BSA.

[muskrat]

G'day Terry,
                acetone can be used as a cross link for mixing methanol with petrol as well. I use Nulon pro octane boost, but have decided to go back to 98 PULP.
I have tried the std needle clip in all positions and none give good results over the whole range. There are about 30 different needles for the Kehin PWK carbs. Needle thickness = 1/8 to 1/4. length = 1/4 to 1/2, taper angle = 1/2 to 3/4. Lots of trial and error.
Cheers

[Hubie]

Going back to your original question about springs Muskrat;

I had a pinging problem with a Royal Enfield Bullet I put a big bore kit in and went up from 6.5 to 8.5 compression and had all kinds of trouble with pinging.  Was only ever under load and the only solution I originally found was to retard the timing.  Problem was it was so far retarded it caused the bike to stall all the time and it had no go higher up the rev range.  After stuffing around with carbs and carb settings I had some stronger springs made for the auto advance unit and all my problems were solved on the spot.

It is well worth the try as it stops the ignition going to full advance too early.

Cheers,

Hubie.

[muskrat]

G'day Hubie,
                 Yep, that's what I thought, thanks for letting me know. But unfortunately it's not that simple for me as I run Boyer with no way of adjusting the advance curve. I had so much trouble with magy's years ago I won't go back. So it's carb tuning till I can find a programable black box. I've ordered needles that richen 0 to 1/2 and lean 3/4. Fingers crossed.
Cheers