Pinging thoughts

[muskrat]

G'day all,
            The never ending ? Just a thought I would like to run by you.
Pinging usually happens under load (acceleration) low in the revs say between 1500 - 2500. If I retard the timing it helps but does not cure. I'm now back to 28 deg full adv and it's still there slightly.
Now the question. Has any one tried stronger springs or lighter bob weights on their auto adv unit to raise the start of the advancement. So it still goes to the same full adv but is retarded for a bit longer.
I know this won't help me with the Boyers but I might have to look for a programmable system.
Cheers

[a101960]

A topic dear to my heart, and might I add a problem that is the bane of my life. I to have the same problem. If I set the ignition to 35 degrees (3/8) BTDC the bike goes like Sh*t off of a chrome shovel. The down side is that it pinks under load. This is most especially noticeable if I hit a gradient and open up to maintain momentum. Changing down will partially aliveate the problem, but crucially I would have thought that with the torque that an A10 has available it should be more than capable of coping. What do I know? Timing at 32 degrees (5/16) BTDC improves matters a bit but backing off a little more is the the only way to eradicate pinking completely. The problem then is that the engine goes flat and woolly. I have experimented with the carb but doing a plug read seems to indicate that the mixture is right at the factory settings. I have now gone up from a 420 main jet to a 430 but I have not had a chance to try this jet out yet due to the weather. Incidentaly the mag and A/R unit have been checked out by Tony Cooper and been given a clean bill of health. The cylinder head has also been overhauled at the Cylinder Head shop (new valves guides and seats). My carb BTW is a monobloc 389 25 pilot, 420 main 106 needle and 3 slide so it is configured on the rich side. My thoughts are that maybe going down the manual advance road might be worth investigating in as much as this would allow some fine tuning of the timing while on the move. Oh, and incidentally I use 99 octane lead free gas (the best available in the U.K.). None of this I know is probally of much use to you, but at least you now know that you do not suffer alone! One more point. Contemporary road tests in the motorcycle magazines of the 1960's stated that RGS and Super Rocket motors would pink under hard acceleration even with 5 star petrol.

John

[Brian]

This is a ongoing problem unfortunately.

I think a friend and me have proved the problem is caused by the fuel we get these days. He has a A10 that pinged but also has another friend who works at a airport, this bloke got us some 100 octane full leaded fuel which we put in the A10. Problem solved, I dont thing it gave any more power than the pump 98 octane unleaded but it ran a lot smoother through the rev range and not a hint of pinging.

Obviously we cant get this fuel so have to work out how to get them to run properly on pump fuel ( I use the premium 98 octane unleaded) My plunger A10 (356 and 7.25-1) and the A7's run fine with no hint of pinging with the timing at 5/16" (32 d)

The 61' A10 has been a problem from the start, iron head, 8.5-1 and 357 cam. Once again timing at 5/16" but that didnt cure it on this one, I found I had to run the mid range richer than I would like, the needle runs in the third groove. If I drop it one groove it pings again, even now on a hot day under heavy load it will still ping slightly.

If only we could get decent fuel.........................

[MikeN]

The cylinder head has also been overhauled at the Cylinder Head shop (new valves guides and seats).

John

 

My neighbours A10 head has also had new valves and seats by The Cylinder Head Shop and it pinks.Whereas it didnt before.
On the other hand I had my head done by them and my bike doesnt.

I realise that the above statement is no help at all .

Regarding  adv/ret .My bike has a lucas competition mag with manual adv/ret. I retard it about half way to start it and then as soon as it starts I advance it fully.After that I dont touch it and its fine.
Mike

[muskrat]

G'day all,
             The reason I asked about the springs and bob weights is I read an article on HD Skirtsters pinging and the solution was to lift the advance curve so it started about 600 revs later. I also spoke to a friend (engine reconditioner) who showed me a new distributor for tin tops that has adjustable pins for the springs to do the same.
 I have tried all manor of carb settings with very little improvement. Raising the needle does help a bit but at cruising is too rich.
I might ring Pazon to see what they say. Keep you posted.
Cheers

[Josh Cox]

My bike was pinging, lifted the needle one slot and it all went away, 7.25 and 334 set as per the manual, also started going quite a bit harder.

Personally I would be playing with fuel before messing with the timing.

As far as I am aware, fuel octane plays an issue only with compression, 8.5:1 should run easily in 98/95 without pinging.

Avgas is 100 octane, whilst I try to run my bike on it, it really does not make much difference.

One simple thing you can try to see if your bike is running too lean is, when riding apply choke/the air level should give a loss of power, i.e. getting much much richer.

http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/photo_18.html

If there is an increase of power / loss of pinging, the engine is too lean.

If you are running leaded fuel, i.e. avgas, the colour of the exhaust pipe stain will give you an idea of the mixture.

[Triton Thrasher]

Sorry if already suggested, but you can raise the needle half a notch, with a bit of shimming/filing.

Also sometimes worth experimenting with smaller needle jet/higher needle position or vice versa.

[muskrat]

Thanks Josh. I am running 10.5:1 and boosting 98 up to 105 so is good by the chart in that link.
Took bike for run today set at 28 deg with just a hint of ping. Came home and reset to 30 deg with B9EGV plugs. Thought you would have herd it in Cairns. Tomorrow lift needles again. I run 2 X 30mm Kehin flat slides with knob type chokes so a bit hard on the moove. At least while I'm tring to sort this out it's getting a longer run in period than usual. 600 miles now.
Cheers

[muskrat]

G'day TT,
             I see you haven't started that bike yet, LOL. The needles on these carbs are a mine field with different tapers, thickness, and length of tapper. But you might be on to it with 1/2 notches. Will give it a go tomorrow.
Cheers

[Josh Cox]

One other thing that was a surprise about this whole fuel thing, apparently the higher octane fuels burn slower that the low octane fuels.

For example the velocity of the average petroleum flame is something in the range 50km/hr, high octane 47 km/hr.

So from what I can recall, if you wish to:

* run at high RPM and use high octane fuel, you will need to advance further to allow appropriate flame time prior to the big flame expansion. i.e. power stroke.

[muskrat]

OK now I'm really going to be busy tomorrow. 1st I'll whack up the timing to 35 with carbs as is on 105 oct. Then try 38. Hope I don't hole a piston. It's hard to read a plug with the unleaded, and even worse with the additives. As well as jetting foreign carbs from scratch. What tangled web I weave.
Cheers

[Triton Thrasher]

G'day TT,
             I see you haven't started that bike yet, LOL.

I gotta getta BSA!

[muskrat]

What a day !! I lifted the needle 2 notches and went up 1 (135 to 140) on mains, new NGK B9EGV plugs, timed at 30 deg. Seemed a little better in the ping department but felt rich. Decided to keep going to town (25K's). Pinging started to get worse and stalled at first set of lights. Limped to mates place and found the neg lead to battery loose. That explained the pinging as the ign was running just of the dynamo, high revs great, low revs ugly. Had a bit of a race with an R1 (rice rockets going to Phillip Island for Supers) and at 95MPH herd the pop. Bugger, head gasket. back to the shed.
Wheels or tits, give ya trouble and cost ya money !!!
Cheers

[Josh Cox]

If it flys, floats or ( insert appropriate word ), its bound to give you troubles.

Do you have a dyno for motorcycles in your town ?.

Racing an R1, good for you  .

[muskrat]

G'day Josh,
               made him take a second look, followed by a shake of his head as he clicked it up a gear and disappeared.
The nearest bike dyno is 130 K's away, but it feels like 50hp (thats drysdales).
Cheers