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Irregular Spark #495534 06/26/13 9:01 pm
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Kev. Offline OP
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what are the causes of an irregular timing spark pattern when on the strobe, mine seems to jump about forward and backwards at all revs, how can I smooth out the timing?


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1973 Moto Guzzi Eldorado
2001 Road King
2006 BMW R1200GS




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Re: Irregular Spark [Re: Kev.] #495539 06/26/13 9:19 pm
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t120mike Offline
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Kev, you possibly have a loose connection which is exacerbated by vibration. Run a separate wire directly from the battery to the pos of the coil (assuming neg ground), make sure of all earths and see if that cures it. Any brief interruption of supply to the coil will cause a spark. If you have a spare known good coil, substitute it. Once the secondary is checked out (it's easier) then turn yor atention to the primary which is more machine-specific: Which bike, what type of ignition?
Machine speciallists may then get the bit between the teeth!
FWIW


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Re: Irregular Spark [Re: Kev.] #495542 06/26/13 9:24 pm
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jfligg Offline
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Kevin just a idea, is there a setting to set the timing to base timing. On cars I have worked on there is a way to set it to base timing then the timing is checked. Jeff

Re: Irregular Spark [Re: Kev.] #495544 06/26/13 9:33 pm
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KarlB Offline
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If it's a standard mechanical auto advance with springs and bob weights then it's usually worn, slack springs or worn pivot points for the weights...:)


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Re: Irregular Spark [Re: Kev.] #495547 06/26/13 9:39 pm
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triton thrasher Online Content
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Or worn pivots for the points themselves.


Amateur Loctite enthusiast.
Re: Irregular Spark [Re: Kev.] #495588 06/27/13 9:46 am
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Dick Harris Offline
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Also cam bearings will cause this problem. Dick

Re: Irregular Spark [Re: Kev.] #495603 06/27/13 12:38 pm
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Al Eckstadt Offline
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Hi Kev, I am guessing we are talking about the Guzzi? I just called my friend Jim who is a Moto-Guzzi specialist. He said the most likely cause on your model Guzzi would be the advance springs, which tend to sag and even fall off. Jim said they are available as a separate item and can be purchased individually.
Keep after it. You'll be riding it soon. Al.


Al Eckstadt
Re: Irregular Spark [Re: Al Eckstadt] #495658 06/27/13 7:55 pm
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panthering Offline
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Hi Kev not sure what type of strobe light you have but some of em have an adv/retard buttons dial in 1 deg adv and see if it holds steady (I have this problem with mine)

Last edited by marcus123; 06/27/13 7:55 pm.
Re: Irregular Spark [Re: Kev.] #495660 06/27/13 8:02 pm
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Kev. Offline OP
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thanks I shall look at some new springs first then, mind you, it is only 43 years old, don't parts last now then?


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1973 Moto Guzzi Eldorado
2001 Road King
2006 BMW R1200GS




Re: Irregular Spark [Re: Kev.] #495698 06/28/13 1:52 am
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RF Whatley Offline
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It's rather normal really. Even if you invest in brand new Lucas auto-advance unit (AAU) and points plate, there's no guarantee it's going away. That's one of the big reasons to fit an EI.


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RF Whatley
Cornelia, GA
Re: Irregular Spark [Re: Kev.] #495710 06/28/13 5:50 am
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You could leave the springs out completely,and it would make no difference at full advance.The weights are jammed solid against their stops at full advance.You are checking the timing at full advance?

The fit of the points cam on its spindle could make some difference.You could do a flash of hard chrome on the spindle to reduce clearance and timing scatter.

If this is something like a Triumph,the fit of the camshaft bushes could make some difference but not a lot.The camshaft will always be loaded downward against the the bush with one intake valve opening and one exhaust valve still well open,when a spark happens.

I've done a lot of distributor work and advance curve modification,and it's not normal to have much timing scatter with points.You could live with a degree or so,but it shouldn't be much more.

Also check that the points gap doesn't vary much around the high part of the cam lobe.If it does,something is bent.It would have to be bent badly to cause a problem.


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