spark knock

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Billpan58
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spark knock

#1

Post by Billpan58 » Mon Feb 14, 2011 3:18 am

out riding 58 this afternoon,getting spark knock on long up hill grades,running 91 octane,engine is not high comp.motor just over hauled.motor was timed w/timing light.using elect. ignition.any ideas appreciated.



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Re: spark knock

#2

Post by Bigincher » Mon Feb 14, 2011 4:05 am

If it was me, I would retard the timing a bit until the knock goes away.
I've never used electronic ignition on my panhead, but I have it on my Shovel and my Evo. I still use the static timing method on all my motorcycles.

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Re: spark knock

#3

Post by Panhead Ed » Mon Feb 14, 2011 2:18 pm

you'v got the timing control in your left hand! go for another ride up that grade and try retarding your timing alittle, it could be your a little to far advanced at the full advance position.... Ed

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Re: spark knock

#4

Post by Cotten » Mon Feb 14, 2011 2:52 pm

Bill!

Re-strobing more to the front of the hole would be prudent, but I still must ask:

Have you installed "tall" sprockets? (i.e.: 24t motor sprocket or belt-drive, 24T tranny sprocket, etc.)

...Cotten

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Re: spark knock

#5

Post by kitabel » Mon Feb 14, 2011 6:51 pm

What spark plug?
How far do you have to back off the throttle to make it stop?

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Re: spark knock

#6

Post by Dave_R » Mon Feb 14, 2011 9:39 pm

I may be the exception to most here on the board, but I only use the timing marks for a general starting point, then it is "adjust by ear" time to get the knocks out, and the power and smoothness I want.

I do not have the twist grip advance (Chopper), so I "lock it down" when I find that sweet spot.

- But that is just my way

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Re: spark knock

#7

Post by Cotten » Mon Feb 14, 2011 10:11 pm

Dave_R wrote:I may be the exception to most here on the board, but I only use the timing marks for a general starting point, then it is "adjust by ear" time to get the knocks out, and the power and smoothness I want.

I do not have the twist grip advance (Chopper), so I "lock it down" when I find that sweet spot.

- But that is just my way
Dave_R!

Unless you have an auto-advance timer,
I certainly hope you are the exception!

And Kitabel!

Whats the sparkplug got to do with it?

...Cotten

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Re: spark knock

#8

Post by john HD » Mon Feb 14, 2011 11:58 pm

i tried to run my '55 FL at FLH specs and got the same result you have now.

where in the timing hole was your mark with the strobe?

john

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Re: spark knock

#9

Post by kitabel » Tue Feb 15, 2011 1:06 am

Whats the sparkplug got to do with it?

You didn't really say that, did you?

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Re: spark knock

#10

Post by Cotten » Tue Feb 15, 2011 5:09 am

kitabel wrote:Whats the sparkplug got to do with it?

You didn't really say that, did you?
Kitabel!

Must I ask twice?

...Cotten

Billpan58
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Re: spark knock

#11

Post by Billpan58 » Tue Feb 15, 2011 8:04 am

mark was in the center w/strobe. yes i do hane tall sproket and belt drive.talked to my builder today he suggests being in third on long grades.

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Re: spark knock

#12

Post by King » Tue Feb 15, 2011 7:42 pm

I've always thought that you SHOULD ping under the heaviest load you encounter. Much of the country I ride is hilly and twisty which means third gear much of the time. But even in third I'm a two fisted rider working the left hand in tandem with the right.

King

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Re: spark knock

#13

Post by Cotten » Tue Feb 15, 2011 8:36 pm

King and All!

Every "ping" you hear is the hammer of pre-detonation beating upon the top of your piston, not only slamming your rings in their lands (grooves), but also creating hotspots upon your piston crown, and robbing precious power and motor life.

The worst "pinging" I have experienced is lugging a stroker with sidehack away from stop-signs with a clack-clack-clack.
Pre-detonation at higher speeds may be slightly gentler, but still to be avoided at all cost, just like lugging at any time.

Many rider-motor-victims of pre-detonation never hear it at all! ("Straight pipes are kewl.")

Even with a hack, a properly set ignition should never need retarding for anything but to start the motor.

(Or with an Indian, to get it into first gear in a civilized manner.)

...Cotten

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Re: spark knock

#14

Post by Panshovevo » Tue Feb 15, 2011 10:32 pm

Cotten wrote:
kitabel wrote:Whats the sparkplug got to do with it?

You didn't really say that, did you?
Kitabel!

Must I ask twice?

...Cotten
Correct me if I'm wrong, but surely there is a reason why they make spark plugs in different heat ranges...

BTW, I've heard of (and experienced) pre-ignition and detonation but this is the first I've heard of pre-detonation.
I was taught that pre-ignition is premature igniting of the air-fuel mixture in the cylinder, frequently caused by hot spots in the cylinder, and is usually identified by a pinging noise. The hot spots can be caused by a number of factors, including incorrect ignition timing, excessive carbon buildup, lean mixture, wrong spark plugs, etc..
Detonation, on the other hand is an explosion of the air-fuel mixture with the resulting effect of a sledge hammer on the piston. Once you have experienced it, you'll know it. It feels like someone has taken a jackhammer to the engine.
I haven't experienced detonation on a motorcycle yet, but let me tell you, when it happens in an airplane and you are 300 feet in the air on takeoff, and there is no way of landing on the runway you just took off from, it will definitely wrinkle your seat cover, if not stain it.

Regards,
John

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Re: spark knock

#15

Post by jibhead » Wed Feb 16, 2011 1:36 am

Panshovevo wrote:
Cotten wrote:
kitabel wrote:Whats the sparkplug got to do with it?

You didn't really say that, did you?
Kitabel!

Must I ask twice?

...Cotten
Correct me if I'm wrong, but surely there is a reason why they make spark plugs in different heat ranges...

BTW, I've heard of (and experienced) pre-ignition and detonation but this is the first I've heard of pre-detonation.
I was taught that pre-ignition is premature igniting of the air-fuel mixture in the cylinder, frequently caused by hot spots in the cylinder, and is usually identified by a pinging noise. The hot spots can be caused by a number of factors, including incorrect ignition timing, excessive carbon buildup, lean mixture, wrong spark plugs, etc..
Detonation, on the other hand is an explosion of the air-fuel mixture with the resulting effect of a sledge hammer on the piston. Once you have experienced it, you'll know it. It feels like someone has taken a jackhammer to the engine.
I haven't experienced detonation on a motorcycle yet, but let me tell you, when it happens in an airplane and you are 300 feet in the air on takeoff, and there is no way of landing on the runway you just took off from, it will definitely wrinkle your seat cover, if not stain it.

Regards,
John
are you saying you have experienced 'detonation' in a piston driven areoplane?

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