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Weak spark

38K views 29 replies 3 participants last post by  lateburd 
#1 ·
I picked up this 2000 sportsman 500 that had an overcharge issue. It pretty much smoked the electronics. The speedo is burnt up. I was getting a no spark issue. I changed the stator/pulse coil all in one. Changed the voltage regulator, coil, coil wire, coil wire end that plugs onto the spark plug. I was at that point only getting 1 spark on the initial bump of the starter switch. I unplugged the ground wire up next to the cdi box that goes up to the speedo and it fired right up. It ran like this for months. Shut if off one day and now it won't start. I have a very weak spark. If I jump 12 volts to the coil I get a bright heavy spark. If I just turn the key over its very dim and weak. Voltage to the white and blue wire from the cdi to the coil is only getting around 2 volts while cranking. Any idea what is causing the weak spark. This thing is about to make me pull my hair out.
 
#2 ·
OK - I don't suppose you know if you have an early or late production model?

Regardless - unplugging the ground wire next to the CDI that goes to the speedo is inaccurate because the only ground wire at the speedo goes to the key switch - which wire did you disconnect? Pic maybe? Neither the battery or the rec/reg has anything to do with spark. Running 12 volts to the coil will usually result in burning up the CDI unit or the coil.

Voltage to the coil from the CDI is typically 100 volts PEAK - you cannot measure the voltage to the coil with a standard multimeter unless you have a peak voltage adapter - use a FLUKE multimeter utilizing the min/max function to measure the peak voltage from the pulse coil and from the CDI unit to the coil.

Since the ignition is AC excited (no battery needed) - a weak spark tells you the pulse generator coil is telling the CDI unit to fire the coil - generally speaking, having a weak, but consistent spark rules out the pulse coil, so the culprit is either a bad ground, the CDI unit or the stator. A no spark issue is easier to pinpoint.

With all that said, how weak is the spark? With a peak voltage tester you can measure the output of the coil - spark plug wire to meter to ground between 20,000 to 40,000 volts. The ******* method is to connect a timing light and with the spark plug in the engine, see if the light flashes - if the light flashes, it indicates the current necessary for a spark has occurred. It does not prove a spark has jumped the gap, but only that the current has flowed. Now your spark plug is not new - as soon as the engine is started and runs a minute or two, the plug is now a used plug. Always use a new plug to test for spark. What brand of spark plug did you put in it? I have seen new Champion plugs that have gone bad after a minute of running and would fire when laid on the head, but would not fire inside the cylinder.

Let me know if any of this helps
 
#3 ·
Yeah, you can replace parts willy nilly in the hopes of getting the faulty one but that can be time consuming and expensive. A much more efficient way as latebird describes is to test and determine which part needs replaced.
I have no way to know since I don't have hands on the machine, but my guess is that if the grounds are good then the CDI is bad.
$15 for a Chinese copy on ebay or $265 from Polaris. I think I'd wager the $15 on a cdi and spend the rest of my money on gas and beverages to go riding... But that's just me. :dunno:
 
#4 ·
I have no way to know if it's early or late model. It would be very helpful because I keep ordering parts that won't work. I ordered a cdi for it for the plug is different so I'm going to have to send it back. I only have a basic Walmart volt meter so I can't test the spark the way stated. Maybe I can borrow one. I also don't have a timing light but I do have a test light. I also don't think that will be sufficient either. Basically every part to do with firing is new besides the cdi box. Very frustrating that it was running one day then not the next.
 
#5 ·
What's the VIN - I can perhaps tell you whether it's early or late by running it through Polaris

Also, why are you replacing parts without knowing the cause of the problem? When it's not running, does it have spark or not? The only need for ignition parts is for a good spark - if your problem is compression, replaciong ignition parts will not fix it.
 
#6 ·
Had to replace parts when I first purchased it because it had no spark at all. The voltage regulator had gone bad and someone rode it with the voltage way to high and burned the parts up. Everything was fine all but the speedometer. It is 300 or 400 dollars.

New parts include stator and pulse coil (picked up as a whole unit), voltage regulator, coil, coil wire, coil wire end (where it plugs into the spark plug), new battery.

I had to unplug the black wire from the cdi box that goes up to the speedometer to get it to spark. Before it would only spark on the first initial push of the start button. Pretty sure the ground goes 3 places. The 4x4 button, the speedometer, and the kill switch. I knew the speedometer was bad so I only disconnected that ground. I left the other 2 hooked up. It actually went I to one plug so I rewired where I could only u hook the speedometer ground.

Everything was going great, ran like a top. Shut it down one day and it wouldnt start back. Pulled coil wire and inserted a different spark plug Grounded to the engine and when it cranks it barely has any spark at all.

I unhooked the blue and white wore from the cdi box to the coil and just one time bumped the male end on the coil with 12 volts and it sparked I assume like it should. Bright white light.

I ordered a cdi box but when I received it one of the plugs wasn't correct. Mine has white and white red wire that goes to pulse coil. Then a red and a black wire that goes to the stator. The new one I picked up has red, black, and green on a 3 prong connector do it wouldn't work. I'm sending that part back and looking for a different one as we speak.
 
#8 ·
In examining the differences in the wiring diagrams the only change that I can find is in the stator, flywheel and CDI units - the CDI charge coil and the battery charge coils have different outputs and the magnets in the flywheel may have different strength magnets - really need to know the VIN to determine what the right parts are. Also, is there a part number on your flywheel, CDI unit or stator?
 
#9 · (Edited)
Got it figured out! :nerd You have a late model based on the plugs to the CDI unit.

The early model has a center tapped CDI charge coil (three wire plug, two wire plug, black kill wire and blu/wht coil wire) and the late model has a non-tapped charge coil (CDI i unit has 2 two wire plugs, black kill wire and blu/wht coil wire)

You would be able to convert the early to the late model magneto, but you need the late model flywheel too.
 
#11 ·
The correct VIN is 4XACH50A2YA333499

Model Name:
SPORTSMAN 500G
Model Year - 2000
Model Number - A00CH50AF = olive green
Purchase Date - 7/1/2000
VIN - 4XACH50A2YA333499
Engine Model - EHSOPLE09
Engine Serial Number - 0053424 late model if after 29083

Flywheel number is correct - FF97

CDI unit part number (if OEM Polaris) is 3086982
 
#13 ·
There is only 7 parts to the ignition - spark plug, spark plug cap, coil, CDI box, stator, flywheel and wiring - a weak spark can be any or all of the parts - generally, it's spark plug first, wiring connections second, spark plug cap third, stator charge coils fourth, coil fifth, CDI box sixth and flywheel last.

Good luck
 
#15 ·
I don't think I have ever purchased anything from ebay before. I do burn up the Amazon prime though! Any recommendations on knock of brand parts? Found one from rareelectrical for $44. The one I just sent back was from dB electrical but it had the other plugs.
 
#16 ·
I'm having a problem finding the correct cdi box. I used the part number listed above and received the wrong cdi box. I just got off the phone with polaris. They looked up part numbers for my Vin number and brought up 3086982 and 3085639. Polaris said both of these are interchangeable but they are not. I need a cdi with two 2 prong ends each containing a male and a female plug. The part I keep getting has a 2 prong male/female plug and a plug that is a 3 prong, 2 males and a female end.
 

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#17 ·
No - they are not interchangeable - 3085639 has the 3 wire plug and 3086982 has the 2 wire plug - 3086982 is no longer available from Polaris, but I know at least one dealer that has one in stock @ $395, but you can change the stator to the early model stator and use the 3 wire plug - the flywheel is the same for both early and late models.

By the way - the charging system for the battery does not power the ignition system - just because it was overcharging the battery, it would not affect the ignition.
 
#19 ·
Well that's interesting! The early and late 2000 500's all used the same engine cases, so either you got a wrong stator or simply didn't have it positioned correctly when installing it. It sucks to get wrong parts, but it happens.

I'm currently working on a Chinese liquid cooled 250 cc VOD engine in s three wheeled scooter - same engine as a Yamaha YP250 that was never imported into the US. The starter drive was defective. I removed the old drive, measured it, counted the number of teeth on the gear and ordered a replacement. Before I installed it, I checked it - it had the same markings as the original, all the same dimensions, same number of bolt holes - a perfect match NOT! It locked up counter clockwise - the one needed locks up clockwise. The only difference is the way the one way clutch is is assembled. I had to order another drive assembly and pay specific attention to the side of the crankshaft it's mounted on to assure it drives the crankshaft in the right direction. The next unit I ordered will only mount with three bolts while the original mounted with six, but this had to do with Chinese engineering. The Chinese do not design parts for a specific application, but adapt readily available parts to the needed application, so buying replacement parts becomes more of a trial and error endeavor. Don't be concerned with the manufacturer of the part or the vehicle, just make sure the dimensions function are correct. The engine might be Aeon, Lifan, Xingyue, Zongshen or whatever, but they may all use a AOYI starter clutch. Some will lock CCW and others will lock CW depending on the specifications of the purchaser. I also figured out how to reassemble the parts to change the direction of lock-up on some designs. It is more cost effective and time efficient to get the correct part the first time instead of reassembling the parts to make it work, but (like the Chinese) if it can be adapted and made to work, do it!
 
#20 ·
Tonight I went back out and went over the whole electrical system again. I think I may have found my issue.

I purchased all aftermarket parts when replacing them before hand. As I stated it ran and drove then one day it was turned off and wouldn't start back. I noticed the plug coming from the stator to the cdi box (a red and a black wire) had been reversed with the plug. So when plugged in the red went to black and the black went to red. Would this allow it to even run at all if reversed?

For some reason the repair manual I purchased for this polaris doesn't included my year. In the electrical section when I get to the year 2000 for all the specs it says not avaliable. From what I have found browsing the web the pulse coil (white to white red) should ohm at 97 ohms. +-20%. I'm getting 121 ohms. Also the (red to black) wires should ohm 1.9 ohms and it's reading 16.5. I'm guessing safe to say it's no good anymore, assuming haveing those two wires backwards have burnt it up. If that's the case what is the chance that the cdi box is bad also? I was just guessing cdi box because other parts were "new".

Should I gamble and buy the stator to match my late model cdi box and hope my cdi box is good? Or should I just buy the early model stator and cdi and just swap it and be done with it? Can anyone give me the part number for the stator that goes with cdi box part number 3086982?
 
#21 ·
First - the red and red/blk wires being reversed would have no effect - those two wires supply AC from the charge coils to the CDI box - AC is AC - reversing the leads still supplies AC to the CDI box so no harm done.

Second - red to red/blk nominal resistance is 19 ohms not 1.9, so it's good - new pulse coil nominal resistance is 97 - resistance typically increases with age and the only to get the exact reading is to use the same meter that was used when the coil was tested for publication of the manual so 121 ohms is close enough.

Note: don't confuse the red/blk wire with the blk wire - blk wire is kill when grounded and red/blk to red is CDI charge coil.

Third - 3086984 is the part number that matches the CDI number you asked about.

I cannot advise you on which parts to get - I would need the vehicle and the parts to run more detailed tests before reaching any conclusions. I would test for peak voltage from the CDI charge coil, pulse generator coil, CDI output to coil and coil to spark plug and then determine which part to gamble on.
 
#23 ·
Set it on the highest DC volt scale and crank the engine - if the reading is point something, then click down a scale - when the reading exceeds the scale selected, go up to the next scale and read the voltage displayed.
 
#24 ·
I'm a rookie when it comes to this electrical stuff so please bare with me. If I did everything correct this is what I got.

Stator peak voltage AC using the red/black and black wire reads 35 volts.

Pulse coil peak voltage AC measuring between the white and white red wires reads 43 volts.

CDI box peak voltage DC between the white/blue wire where it plugs into the coil and to ground reads 1.6 volts.

Coil wire voltage with positive side inside end of the plug wire and ground on the engine reads 54 volts.
 
#25 ·
There is a problem - the voltage on the black/red to black wires should be 140 VDC

Pulse coil white to white/red should be 2.5 VDC minimum, so it's probably good

The blu/wht wire going to the coil should have 130 VDC minimum - low volts in = low volts out - at least pulse coil is triggering the CDI so the pulse coil and the CDI box are probably both good

If you don't have sufficient voltage to the coil the coil's output to the spark plug is irrelevant

You need a new stator or a new flywheel - either the windings are bad or the magnets are weak - go for the stator, magnets seldom go bad, but the other parts fail frequently
 
#26 ·
Awesome, thank you for all the help. Seems like everything I've been ordering has been coming with the early year style plugs. I still have the new cdi box that I haven't sent back yet. I will order a stator with the same 3 prong plug and swap it all over. Do you happen have the part number for the stator I need to fit the cdi box below?
 

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