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Discussion Starter #1 (Edited)
Hi All,

I have a 2010 500HO that seems to hesitate or miss on acceleration under load. I took my son to the gas station and while we were headed there, during acceleration from a stop, it would miss. I should mention too, it has a miss at idle but no discernible miss when in punching the throttle in park. The idle miss is confirmable using a timing light. It is absolutely possible this miss is also occurring under load and noticeable in park, off idle. The carb has been off half a dozen times, super clean, blown out all the jets (new carb kit), ran seafoam through it etc. I'm at a bit of a loss here. I am going to see tonight if the fuel pump is pumping as it should. It does mange 55 MPH but, misses as you are holding WOT. I can ease into the throttle up to 25MPH without noticing it but after 1/4 throttle it starts to become noticeable. The rpm gauge is inaccurate without the lights on if that matters? Anyone experienced this? I'm stumped and don't want to just throw money at it. The ignition should fire every time regardless the situation in the combustion chamber, right?

Carb Cleaned
Seafoamed
New Belt
New filter
Cam is good
Valves are clearanced
No gas in oil
Carb clean tested the intake boots on both sides of the carb

Things i have considered (but don't want to throw money at yet, i'm done doing that):
Pickup coil? - doesn't pickup up every time?
Ignition coil? I did get it to jump a "10,000V" Gap with a spark tester
CDI? But why? lol
 

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Spark plug - spark plug cap - electrode gap?

If you are visibly missing spark (confirmed with timing light) then why are you working on the fuel system? Work on the ignition system. Unless the fuel system is causing a fouled plug, then work on the fuel system. Always perform testing with a new spark plug even if the plug is only a week old. My opinion is a spark plug in not new anymore if it has been used to run the engine. All spark plugs are used unless they are in a box and have never been in an engine.
 

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Discussion Starter #3
I worked on the air system. Checked out. Then to the fuel system because it did have a couple fueling issues that seem to have sorted out. Then on to the ignition system. I guess since that’s the order I do it on my classic car stuff it’s just a thing I do. Now that I am onto the ignition system, and done some preliminary testing on a brand new spark plug, I can get the spark to jump a 10,000 volt gap (1/8” gap) but it’s kinda orange. But I haven’t found what the output voltage of the coil should be. What little info I have found on small engines, it’s around 5,000. (Riding lawnmowers and such) the spark looked decent off the side of the engine and it throttles up decent. I don’t want to throw a coil at it if it’s something else. I’ll run through the standard electrical tests for the rectifier and stator/CDI tonight to narrow it a little closer. I posted here for that “same thing happened to mine and it was .......” you know? To narrow it further.


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Orange spark is typically weak - it should be blue to white and it should jump 1/2 to 1 inch - I never measured the voltage from the coil to the plug, but I have been taught it is typically 10,000 to 40,000 volts peak - it will vary from make to make and model to model. Check the spark with the plug cap removed.
 

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Discussion Starter #5
Orange spark is typically weak - it should be blue to white and it should jump 1/2 to 1 inch - I never measured the voltage from the coil to the plug, but I have been taught it is typically 10,000 to 40,000 volts peak - it will vary from make to make and model to model. Check the spark with the plug cap removed.


That’s what I was thinking. Orange is week unless you are testing over the voltage rating of the coil. I will check the resistances for .3 primary, 6.3k secondary. Should be able to discern transformer ratio from that.


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Discussion Starter #6
I've been thinking a little about this, running around the web for answers, and came across a suggestion from RM stator. If the gap between the pickup coil and the flywheel is too large, less voltage will be going to the cdi to signal the ignition coil. A gap of .015" will produce 8-12 Volts but a .045" gap could produce as low as 2 Volts. So if the gap is off just slightly (give or take .010") this could produce a weak voltage to the CDI and in turn crappy signal to the ignition coil primary.

I will perform the following tests before opening my wallet

Pickup coil gap check (if voltage check is low)
Pickup coil output voltage check (ignition wire disconnected)
Ignition coil input voltage check (looking for 12V here)
Ignition coil primary and secondary resistance checks.
Stator Voltage checks just to be sure


So i think I've got it narrowed down to the above two coils with a stator check to top it off. Coming from a car background there are no pickup coils so i would have never thought of this.

Not a lot of information out there on intermittent spark miss
 

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OK - I have been reading the service manual - lo and behold, this Polaris does not have a CDI ignition! It is referred to as a CDI but is nothing more than an electronically controlled ignition. Similar to what Kawasaki used prior to installing CDI on their vehicles.

Electronic controlled ignition is a simple method of replacing points with an electronic switch. 12vdc is supplied to the coil and when the pulse generator tells the control unit (ECU - electronic control unit not CDI - capacitive discharge ignition) to fire the spark plug, the 12vdc is interrupted, the magnetic field around the coil collapses and generates the voltage necessary to create the spark.

Knowing this, if you n=have 12vdc to the coil and the coil has a good connection to ground, a weak spark is the result of a bad coil, bad spark plug cap, bad spark plug or a bad connection between the engine and the coil ground.

Polaris should be sued for false advertising - electronic control is not capacitive discharge ignition unless in some convoluted way the ECU is using capacitive discharge to interrupt the flow of current to the coil. Most ECU's use SCR's to stop current flow that results in a spark.

If you have intermittent or weak spark it could be the ECU or the pulse generator, but is more commonly the components listed previously. A weak signal from the pulse generator could result in an SCR not stopping current flow completely, but it would have to be 'right conditions' for it to happen. It is not the norm. Too little voltage from the PG and the SCR fails to fire and spark does not occur. Normally if the SCR is triggered, spark is good. With EC ignition, spark may be fine with as little as 6 volts from the battery. The PG voltage has nothing to do with the voltage output from the coil, is used only to trigger the SCR.

Now I got to get with God of Thunder - his 330 he is having problems with has the same ignition as this 500.
 

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Discussion Starter #8
So that said, I will grab a coil just in case but determine all other resistances and voltages first since coils are not returnable once opened. I will have to modify the connections a bit on the replacement since the aftermarket is a bit different, for $40CDN where the exact Polaris part is $260 plus $70 for the cap. Yikes. So the PG is only the activation of the signal and is completely separate from the signal to the coil? Makes sense to use a relay analogy the PG turns the relay coil on and off and the relay contacts are the coil power. I agree a weak PG signal could perhaps not fire the scr to energize the ignition coil creating a miss.
Will check it all out


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Discussion Starter #9
Pickup coil good
Ignition coil good primary and secondary
Stator windings good
Timing is right on

I’m back to carb I think. Would a no atomized fuel cause a ignition miss visible by timing light?

Carb is not dirty. Although the pilot screw is frozen in its well but factory set
Can the main jet tube be removed? I have replaced the jet needle and needle and seat and main jet.


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Discussion Starter #10
I’m at a loss. Electrics check out. Carb is super clean. Rebuilt. Tried it with the spark arrester plug out. Everything seems good. Valves are adjusted cam lobes aren’t fried. I don’t know. The miss is enough to bog the bike while accelerating. Time to sell it. Lol


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Pickup coil good
Ignition coil good primary and secondary
Stator windings good
Timing is right on

I’m back to carb I think. Would a no atomized fuel cause a ignition miss visible by timing light?

Carb is not dirty. Although the pilot screw is frozen in its well but factory set
Can the main jet tube be removed? I have replaced the jet needle and needle and seat and main jet.
The 'main jet tube' as you refer to is the needle jet. It is imperative that it be removed when cleaning the carb as it mixes fuel and air together before the mixture enters the air stream in the venturi. It is supposed to be replaced when replacing the slide needle.

Also, the pilot screw has to be removed when cleaning the carb or the cleaning is not complete. At best is was a partial cleaning regardless of how well, how many times it was done or what method of was used. But, the pilot screw only affects idle, so if it idles well, don't worry about it.
 

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Discussion Starter #12
It idles really well it’s just every couple of seconds I get a miss that is detectable by the timing light. It spools up well in park and accelerates well but at about 20mph it will buck every time it misses as it accelerates. The pilot screw is knackered. But I was able to confirm its circuit is clear. I guess I will check the valves again. I am getting about 70psi on compression test. But even if it had no compression it should still fire the plug every time the trigger coil is activated by the flywheel. It generates a little over spec (.15VAC) of the output In the manual. I just don’t get how it would fire 6-15 revolutions then miss one, fire 6-15 revolutions. It’s not the same count every time. Ahh.


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At this point, if I were working on it, I would try a different coil. If you suspect the ignition, the coil is the easiest to change and usually the cheapest component. Also, coils will fail in many ways.

I had a KZ650 Kawasaki that would not start cold. Ether wouldn't fire, boosting the battery didn't improve it, kick starting was a fail, but if you cranked the engine long enough it would finally start. You could ride all day long, shut it off and have lunch and it would restart without a problem, just don't let it sit overnight or the starting was the same. I replaced the spark plugs, plug caps, points, condensers, battery, adjusted the valves and cleaned the carbs - nothing helped. I had checked spark and it had spark, it just wouldn't start cold. Finally in desperation, just to find out what would happen, I borrowed some coils off a 550 Honda. The would not fit the mount, but I could bolt them up with one bolt just for testing. I touched the starter button and it fired instantly. I let it idle to warm up, then installed the original coils - it would not start! Come to find out that if I turned the key on and walked away for about 5 minutes letting the coils warm up from current flow, the bike would start easily. I was familiar with coils being fine when cold and failing when hot, but this was the first coils that I had seen that would not fire cold and were fine hot. Not only that, but the bike had two coils and they both failed the same way at the same time. However improbable not impossible.
 

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Discussion Starter #14 (Edited)
I have a new coil at home I will put it on and see. I guess you don’t know until you try it. At worst I’m out 45 bucks and still digging. It does blow fuel mist out the front of the carb at WOT but with timing good, valve lash and cam lobes and compression good I chalk it up to carb design mikuni BST40. It doesn’t backfire or pop through the carb and the airbox is dry, intake tube has a wee little bit of mist on it but that’s it. I'm going to check the float level and ensure its correct. (i may have set it too high book says 13mm on the set but another post i read showed float even with the carb body. I will replace the coil and set the float and report back. i love trying to solve multiple issues at once! lol


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Discussion Starter #16
Well, I leaned out the carb and it runs like a champ off idle. I mean, it idles well but still has an ignition miss but I’m not as upset about it since the hesitation during acceleration appears to have been to Rich a fuel mixture. Accelerates good without hesitation now. All the way to 55mph. I’m happy for now! I did make my own peak voltage tester for $6 instead of the $50 retail. Spark test jumped bright blue across a 20000 volt gap. All things in spec voltage and resistance wise so I’m still stumped on the idle miss. If I end up finding out what it is I will report back.
Cheers
Adam


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Discussion Starter #17
Still got the idle miss. Looks like the rpm issue on the display appears to be internal to the speedo. Possibly a solid state part breaking down because it reads right at first then fades and doesn’t follow the input voltage from the rectifier until I turn the low beams or put the brakes on. I may ground the brown wire closer than back to the battery ground bolt but it didn’t seem to make a difference when testing it. Something to do with the light resistance. Weird.


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