weak spark

[Derek Young]

I've been having some trouble starting my engine lately, especially when hot.  Was thinking it was dirty carbs so I cleaned them up, also adjusted valve clearances and installed a new starter.  It generally starts up pretty well now, but after a few minutes of riding starts missing and losing power.  It will still run and drives, just more shitty than good.

Checked the resistance in the coils, within spec.  resistance a little high on the pickup coil.  Spark on all four is there but very weak.  Leaning toward a faulty igniter box.  Any way to test these?  Its an 86.

Missed out on our labour day road trip to the Kootenays.   Going to Bannf/Jasper in the truck instead.

Thanks in advance
Derek

[FJ111200]

What sort of condition and age are the spark plugs?
If you haven't already done so, i'd start there before the igniter box.

[Dan Filetti]

What makes you think it a weak spark (the subject of the post)?  My guess is that it's fuel, rather than spark.  This could easily be fuel line routing or the carbs may still be clogged.  Alternatively it could be the age-old gas cap venting issue.  Ride around with the gas cap cracked open and see if the problem still happens.  Also, if it's the gas cap venting issue, then the behavior will be worse with a full tank and the cap latched.  I'm kind of doubting that it's fuel level, but other may have more insight on that. 

Dan

[SlowOldGuy]

I've read that on "most" ignition systems, you can NOT judge the quality of the spare by how it looks to your eye.  That small blue spark may be just as good as the fat spark you're anticipating. 

Better to perform a more objective test on the components than passing judgement on what "looks" good (or doesn't).

DavidR.

[Pat Conlon]

David is correct, "seeing" is not believing....Ya gotta feel the difference. Hold the plug in your hand and see if you can "feel" the difference...

[craigo]

David is correct, "seeing" is not believing....Ya gotta feel the difference. Hold the plug in your hand and see if you can "feel" the difference...

I just love the feeling of getting hit by a really hot coil.  Almost as fun as getting hit by a florescent ballist.  You know what I mean, Vern???    

CraigO

PS: Pat, are you still riding???

[Pat Conlon]

Yea, what the hell. I can't dance.....

[rktmanfj]

Yea, what the hell. I can't dance.....

Come back to TPTN next week, and Henry can teach ya...       

[Derek Young]

David is correct, "seeing" is not believing....Ya gotta feel the difference. Hold the plug in your hand and see if you can "feel" the difference...
[/quote
I believe. The proper technique is to shove one plug in my ass and put my tounge on another while hitting the start button.... just like you showed me at the rally

[Derek Young]

Had month old plugs in, same behavior when I put new ones in.

Fuel line routing hasn't changed.

Long since removed the tank vent flapper.

Bowls have fuel in them when I cracked the drain screws.

I tested the. Spark at night, very faint. Tried the same plug on one of the wires in my car and wow! What a difference.

Yes, I agree, i'd like to test the parts more also, but my clymer manual only suggests testing resistance on the coils and no test for the igniter box. Does anyone know of a way to test these.

Derek

[Shaun]

Derek did you get this sorted out? Have you done the coil relay mod, it may help out your weak spark/hard start issue. Check the file section for the mad there is a good write up with pics in there.

Shaun

[Derek Young]

Hey Shaun.  Did the relay mod on Monday.  Went from 10.5 to 12.6 volts at the coils.  The spark still appears weak.  Bike still runs fine untill it gets hot.  Hope to have time to sort it out this weekend.

Derek

[Shaun]

Well that would be one issue eliminated, just as a side thought is your heat shield in good shape? No vacuum leaks anywhere and did you move the needles down to the third position and give that a try, still think the second position my be a little thin with the airbox modded.

Shaun