E: Engine Ignition Advance

[greg brillus]

Detonation can cause many different kinds of problems, not just a big vent in the piston crown........If you remember Ken and Barry Horner had issues with detonation causing a high frequency through the piston and connecting rod........This ultimately caused the rod to fail........ I have heard that running methanol or E 85 type fuels can cause detonation high frequency problems that relate to the fuel used. There are many images of pistons on the net showing damage from detonation that show clearly the effects of destructive shock waves that break either the rings and/or the ring lands.........This is what has happened to your piston..........so on part throttle how do you know what the mixture is.......This is where plug checks can be helpful........Plugs that look absolutely clean after a run are a sure sign the mixture is definitely on the lean side for an air cooled engine........Even if you run the bike up an incline in say 3rd gear and the throttle held in a certain position........ Then pull over quit the engine and remove the plug and have a look. I don't recommend you use 98 octane fuel, use 91.......91 remains constant and more stable for longer.......98 goes off after several weeks in the tank and leaves a fuel not much different to kerosene.

 

[Martyn Goodwin]

been running 91 for a year or more. After a run my plug is very sooty around the outside with the centre ceramic a very dark coffee colour

 

[greg brillus]

That sounds good.......What plug are you running........I am generally using Champion N5C's in all the bikes now. They handle the sooty mixtures better without fowling up. I remember Ken Phelps prefers them as well.

 

[Martyn Goodwin]

On advice of the late Big Sid I had been using Nippon Denso W22EP-U plugs for years - and have plenty of new old stock on hand.

Just lately I switched to NGK BPR7EIX iridium, gaped to 0.018" as a trial, mainly to avoid plug fouling.

Here is a photo of the NGK plug after a 10 km run yesterday - no extended idling. Would rather run rich than lean!

 

[stu spalding]

Hi Martyn,
Try putting a socket over the bolt head and giving it a gentle tap, this should set the tapers and prevent the armature moving. Cheers, Stu.

The hardest bit of all is setting the timing as the ATD tends to move as you tighten the retaining bolt. Patience and swearing helps!

 

[greg brillus]

A number 7 plug is a bit cold, better off with 5 or 6.......All those fancy fine electrode plugs are a waste of time......Even for racing you are better off with normal full width electrode plugs........Much bigger spark. It does look a little on the rich side, but that is better than too lean.......A Champion plug would look better than that.

 

[Bill Thomas]

Try Stopping the engine after doing 70 ish for a mile or so, And checking the plug,
It's hard to do, Because just a few engine turns can mask the result.

 

[oexing]

All that talk about detonation - and then using 91 octane fuel - now I try to see the logic ?? So why have they come upon 98 or 100 octane fuel or avgas that had still higher octane rating in the past ?
There could be some truth about detonation in this engine which wrecked the piston ring. But then why on earth keep using 91 octane fuel at all ?
Also I´d like to see the advance curve of the ATD in this case. No use stating advanced and retarded degrees when not telling at which speed you have full advance. I´d like to have full advance NOT before 3000 rpm crank speed, maybe 3500 better. And mixture seems very rich, could lead to thinned oil from that, no great lubrication then. Some more photos of piston crowns would be good for drawing conclusions and to learn from. For knowing about mixture you´d better look at the piston or spark plug thread face, not the ceramic. Black sooty deposits are very rich , so go for the carby. When that is fixed you pick any spark plug that keeps the ceramic nice and bright - and this depends on your riding style, pottering or high speed motorway burns - very different conditions for plugs.
As long as you see a sooty piston crown I cannot believe in overheating effects , you´d have non deposits in that case but melted edges or worse. I remember one story decades ago with an all iron HD Sportster of my neighbour , got a holed piston from using "regular fuel" then because the guy from the filling station suggested to save the money by not having high octane fuel.

Vic

 

[Martyn Goodwin]

All that talk about detonation - and then using 91 octane fuel - now I try to see the logic ?? So why have they come upon 98 or 100 octane fuel or avgas that had still higher octane rating in the past ?
There could be some truth about detonation in this engine which wrecked the piston ring. But then why on earth keep using 91 octane fuel at all ?
Also I´d like to see the advance curve of the ATD in this case. No use stating advanced and retarded degrees when not telling at which speed you have full advance. I´d like to have full advance NOT before 3000 rpm crank speed, maybe 3500 better. And mixture seems very rich, could lead to thinned oil from that, no great lubrication then. Some more photos of piston crowns would be good for drawing conclusions and to learn from. For knowing about mixture you´d better look at the piston or spark plug thread face, not the ceramic. Black sooty deposits are very rich , so go for the carby. When that is fixed you pick any spark plug that keeps the ceramic nice and bright - and this depends on your riding style, pottering or high speed motorway burns - very different conditions for plugs.
As long as you see a sooty piston crown I cannot believe in overheating effects , you´d have non deposits in that case but melted edges or worse. I remember one story decades ago with an all iron HD Sportster of my neighbour , got a holed piston from using "regular fuel" then because the guy from the filling station suggested to save the money by not having high octane fuel.

Vic

Hi Vic, see my post #7. I have a non contact tacho on order so I can measure the rpm where the advance starts and also the rpm where full advance is reached.

In my post #6 it seems that full advance is reached at around 2,500 rpm with the standard ATD.

As part of the recent changes I have lightened the ATD bob weights in order to raise the RPM point where full advance is reached. photo in my post #6

Once I get the tacho all should be revealed regarding the action of my atd.

Martyn

PS my 'revised' signature says it all.

 

[vibrac]

Hi Martyn,
Try putting a socket over the bolt head and giving it a gentle tap, this should set the tapers and prevent the armature moving. Cheers, Stu.

It took a real motorcyclist who had suffered like all of us with the prince of darkness silly tapered mag to atd connection to come up with the BTH electronic mag through peg
It really goes to show what a passive customer the pre and post war motorcyclist was no wonder Vincent's went bust pearls before swine comes to mind.