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Does This Sound Like A Bad Coil?

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So, since I got this 2005 YZ450F a few months ago, it's had a bad hot restart issue.  Cleaned the carb and replaced the a/p diaphragm and it was better for awhile,  but every once in awhile would still fall on its face and not want to restart.  Then 2 weeks ago in Moab, I had a horrible hot stall and restart problem.  So, when I got back I went and did my valve adjustment and every thing is in spec now.  Cam marks, and flywheel marks all line up, chain and tensioner were in good shape so reused. 

 

I researched the jetting section of this forum, and have dropped from 165 main to a 160, 45 pilot to 42, and stock NFLR needle from clip position 4 to clip position 3.  Fuel screw 1.25 turns out.  Now throttle response is good, except a little flat off closed idle.  Weird thing is now when I hit the kill switch, 2 seconds after the motor stops turning, it shoots a flame past the spark arrester.  Also when revving, there is a single loud pop when closing throttle, but not much popping when riding on decel.  I figure that is because the pilot is still too fat and should be dropped to a 40 or 38.

 

Despite making all these changes for the better, the stalling and restarting has gotten worse.  Today was my first ride since the valves and jetting, and she was running great!  Best midrange response it's had.  But then out of nowhere after an hour or so of riding.  It kept stalling for no reason, and was acting very weird on restarting.  It was as if the plug had fouled, but it was a brand new plug.  After several minutes of kicking, finally restarted.  Went back to the truck and took a break, and didn't want to restart.  Finally got it started and ran fine for 10 minutes, then stalled on a trail going downhill like I hit the kill switch.  Rolled for 20 feet still in gear and it never restarted.  Was stranded in the back field of my local track for 20 minutes, finally got it restarted and got back to the main area.  Went to do a lap on the track, and as I was pulling on, same thing, just fell on its face.  Also, many times while kicking, bike would fire for a few revolutions, then nothing for another 10 kicks.

 

So does this sound like the ignition coil is crapping out?  Always runs like an angry ape after initial startup, pulling the front wheel no problem and great throttle response.

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The jetting your started with is correct.

You have an electrical problem

I would do the factory stator test, and test the plug, plug cap, plug wire, stator harness plug, and all grounds.

If it starts fine cold, as in start it, kill it, start it, kill it, etc....but when hot it won't re-start, that is a classic 'bad stator' symptom.

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Are testing procedures in the service manual?

 

Also, I'm in Denver, at 5,300' of elevation, current temps over 80°F.  Would current jetting be correct, or my old jetting be correct?

Edited by High On Octane

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45 pilot is correct for anything below 8000 feet, usually.

It sounds like you have skipped a cam tooth. If you have not changed the timing chain and tensioner from stock, it's over due.

 

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2 minutes ago, Krannie McKranface said:

45 pilot is correct for anything below 8000 feet, usually.

It sounds like you have skipped a cam tooth. If you have not changed the timing chain and tensioner from stock, it's over due.

 

Even with the 42 pilot, I can turn the fuel screw all the way in without the bike stalling.

 

The chain and tensioner were replaced by the PO when he did the Athena kit, which I believe was only Like 20-30 hours ago. Like I said, when it runs, it runs great until it gets hot.  When I first jump on, it pulls harder than any other machine I've owned, its almost scary at times.  But then it gets hot and becomes a royal PITA to get started again.  Like I mentioned, same symptoms in Moab before I touched the valves or jetting.

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1 minute ago, High On Octane said:

Even with the 42 pilot, I can turn the fuel screw all the way in without the bike stalling.

 

The chain and tensioner were replaced by the PO when he did the Athena kit, which I believe was only Like 20-30 hours ago. Like I said, when it runs, it runs great until it gets hot.  When I first jump on, it pulls harder than any other machine I've owned, its almost scary at times.  But then it gets hot and becomes a royal PITA to get started again.  Like I mentioned, same symptoms in Moab before I touched the valves or jetting.

Ah yes, big bore means stock jetting will be rich, a bit, and slightly smaller jets will be in order.

Right before you kill the engine when hot, is it running ok?  If yes, it's not the stator. If not, it's probably the stator.

When trying to start it hot, have you tried using the hot start? If no, you should try it.

 

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1 hour ago, Krannie McKranface said:

Ah yes, big bore means stock jetting will be rich, a bit, and slightly smaller jets will be in order.

Right before you kill the engine when hot, is it running ok?  If yes, it's not the stator. If not, it's probably the stator.

When trying to start it hot, have you tried using the hot start? If no, you should try it.

 

Most recently, after 20 or 30 minutes of riding, low end bog has gotten when hot.  If it's been running for a bit and I kill it, it's hot or miss with the restart.  Which is why I'm thinking ignition coil, because it's almost as if it just shuts itself off.  Also, something else that's making my think coil, is because when I replaced the spark plug at valve time, it only had 20 hours in 3 months on it, and the base of the plug was noticeably corroded, and there was a black ring around the top of the plug near the top cap, that could have been a carbon track, but initially thought was just dirty.

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Coils usually do not get 'worse', they either work or they don't.

Again, have you tried the hot start?

Have you tested the stator?  Hard start or poor running once hot is a typical stator failing issue, but not necessarly a hard to start when hot issue``

Have you inspected the plug cap for internal arcing?

 

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Hot start has zero effect.  Stator is testing good and in spec.  As I figured, coil is testing suspect.  Secondary resistance is ok, but primary resistance won't hold steady, and spiking .2 ohms above spec.  Spec is .08-.1,  but resistance is topping out at .3 ohms.  Manual says anything above or below spec should be replaced.  Of course because it is coil-on-plug, the factory replacement is over $100.

 

Anyone have any experience with CoilSpec coils?  Claim to have a 2 warranty and only $26 on eBay.

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Well, after making a dealer inquiry with CoilSpec, I wasn't very impressed with their answers or their offer.  Rather than actually make an attempt at offering the dealer information I asked for, they sent me a discount code which brought the price from $39.95 to $31.96 (20% off).  Which would've been fine,  but they are on Ebay for $25!  So, not at all what I was expecting.

 

 

So, in an effort to work out a better deal and possible long term business relationship, I brought the pricing to their attention.  And also asked what sets them apart from the competition of other aftermarket coils, and they responded with:

"Sure I understand. We offer a more accurate and reliable product than your typical ebay seller. We are used in race applications and we are always improving our products to set ourselves apart. Customers also appreciate the extended 2 Year Warranty."

 

Very indirect and didn't really answer my questions, but in fact opened up more questions.  Like, Are customers appreciative of the warranty because they actually need it?  How often are these coils being warrantied out?  If your coils are used in "race applications" why not mention a name or style of racing?

 

Needless to say, whomever I was emailing with was just interested in making a single sale, and not a business relationship.  Unsatisfied with how the conversation went, I decided to stop pursuing the aftermarket possibilities and went with a stock coil.  My local dealer had one on the shelf, unfortunately I get a crap discount from them.  But, still sounded better than worrying if the aftermarket coil would fail.

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STATUS UPDATE

 

Installed the new coil last week and took her out to the track over the weekend.  For the first time since I've owned the bike, I rode for the entire day without the bike stalling once.  And also restarted within the 3rd kick every time all day.  So stoked to finally have the stalling issue figured out!

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Hi. I have got a problem. My yz450f 2009 start with just 1 kick and work fine and on accelaration and declaration is fine but when at the staedy and static trothle have some sputter .i think coil is bad. Or what else do you think. It works like choke. But not in the chok.pa pa pa pa. Like this

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4 hours ago, synopsys said:

Hi. I have got a problem. My yz450f 2009 start with just 1 kick and work fine and on accelaration and declaration is fine but when at the staedy and static trothle have some sputter .i think coil is bad. Or what else do you think. It works like choke. But not in the chok.pa pa pa pa. Like this

Could be the coil, but more likely you have a carb problem.  If it starts and runs good, but sputters at partial throttle, it's possible you need the needle at a different position.  Possibly a different needle all together.  If you had coil problems like me you'd be losing spark all together.  Just my 2 cents tho.

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