Kx 250 lemon

[DemonRanger]

Hi guys, new to the forum! Making an account here however i've done some reading here before. I need some help with getting my dirtbike running. I am very frustrated with it as i haven't had the chance to even enjoy it since ive bought it. I've had maybe two good runs on it. Anyways here is the background:

 

2001 KX 250 2 stroke, Fully rebuilt top end and bottom end done by local garage. After the rebuild the bike was running pretty good. However I have had a issue with it losing spark. Took it for a good spin one day and the bike lost power suddenly and died. I started troubleshooting it, and found that it had no spark. So i went ahead and checked everything out and found out the new stator that the garage installed on it either developed a short or some type of issue. I checked it with my multimeter and proved that it indeed was faulty even though it looked new. So i threw the original stator that i had for the bike back in it and the bike had spark again. Yesterday, I filled it up with mixed fuel and had it running. Bike started fine and everything seemed good, however about 5 minutes after it warmed up it died. I checked the plug and it was full of fuel. So i was thinking it just flooded itself and no big deal. I then went and put a new spark plug in it ( tried an iridium plug as i read online that they are suppose to be better ) , bike started up fine and I was impressed with it, however after about 5 minutes of trying to warm her up the bike started to act boggy and i could feel the bike trying to die, shortly after it died. I kept kicking it over for a while and no go. So i then troubleshot it again today and now theres no spark again.

 

I am very disappointed as the issue seems to be back to square one. Anyone have any input or advice, im at a lost cause with the bike. It's like when it warms up she gets boggy then doesn't want to start any more. Also i found it strange that the brand new stator became faulty or damaged and now with the old stator i am no longer getting spark. I had the motor fully rebuilt with wisco parts because i was hoping to take care of the bike, however i can't seem to drive it!

 

Much thanks for any input. 

[Yamahace]

Aftermarket stators are known to be bad even new. I'd look for an own one if that's not what they used. Also I'd check to see if they used a wiseco crank. They are well known for being crap.

[MatthewMCRepair]

Just a thought here: maybe you are fouling the plug and therefore not seeing spark. Can you confirm if you have spark with a BRAND NEW plug real quick?

[DemonRanger]

Hi there , I did try three different plugs I had , one brand new , the other one almost new that I cleaned and the iridium one I bought recently. No spark with either 3. When she was running it was dying once it was warmed up. When it was cold it would start up usually first kick. I'm gonna pull the stator again tonight and check it out but I'm pretty stumped 

[Texan]

I'm wondering why they would've changed the original stator, unless it was bad. In that case, it would still be bad.

Also, have you checked the connection between the spark plug boot and wire?

[DylDog]

i have never experienced it myself but have heard of faulty CDI's that only seem to show symptoms when warmed up.  You can simulate it by testing with a ohm meter when cold then again after warming up with blow drier.  I would also be skeptical of the spark plug coil.

[Jeekinz]

You can DIY test the stator and coil with a DMM per the factory service manual.

[DemonRanger]

Hi guys , so for giggles I tried another new spark plug again today and the bike got spark back. Very strange as I tried a few spark plugs. I tested the stator and it tested fine. Not sure how to test the ignition coil. I tried starting the bike again with the new plug and it started first kick again. However after about 5 minutes of warming up it died again and no more spark. Any more ideas ? How do I test the ignition coil ? Thanks ! 

 

Also how do I test the Cdi?

Edited June 2, 2017 by DemonRanger

[Jeekinz]

15 hours ago, DemonRanger said:

Hi guys , so for giggles I tried another new spark plug again today and the bike got spark back. Very strange as I tried a few spark plugs. I tested the stator and it tested fine. Not sure how to test the ignition coil. I tried starting the bike again with the new plug and it started first kick again. However after about 5 minutes of warming up it died again and no more spark. Any more ideas ? How do I test the ignition coil ? Thanks ! 

 

Also how do I test the Cdi?

It's all described in the Factory Service Manual (FSM).      scribd. com/kidkawie

You can test the stator and coil.  You need a dealer to test the CDI.

 

[DemonRanger]

13 minutes ago, Jeekinz said:

It's all described in the Factory Service Manual (FSM).      scribd. com/kidkawie

You can test the stator and coil.  You need a dealer to test the CDI.

Hi , I appreciate the reply. I'll try to find a copy online. I tested the stator as there's only two pins to check. Got the right resistances on the old stator that's in the bike currently. Also I checked the brand new stator that I had. One of the pins don't have connection. The new stator that I had was OEM. Weird how it became shorted or damaged. 

So stator in the bike proves to be good according to tests.

i swapped out my cdi with another spare that I had no difference.

only thing left I can think on is testing the ignition coil ( spark plug wire ) and the silver block on the neck of the bike .  Thanks for all input so far 

 

 

13 minutes ago, Jeekinz said:

 

 

[DemonRanger]

Maybe it's a fuel issue ? Or maybe I just found another issue.. so today I tried switching out the rectifier and went through the harness. Had the bike running for about 5 minutes again then it started to die . So I went and parked the bike again, came back 20 minutes later and found a puddle of fuel under the bike and dripping fuel. The fuel is coming for a hose down under the carb by the rear shock. Maybe the carb needs to be cleaned and that's why she keeps fouling plugs after 5 minutes ? Or am I grasping at straws 

[MatthewMCRepair]

Sounds like you have multiple problems. Here is a carb clean video and float pressure check:

 

 

 

 

[Bron-Yr-Aur]

I'm shocked at how many of these threads I see, yet rarely do people mention the pickup coil. So many people start jumping to the worst case scenario (CDI) even though they rarely go. Same thing with the stator.

 

Your symptoms scream pickup coil to me. They crap out as the bike warms up and gets hot. (And the puddle sounds like a stuck or dirty float needle valve.)

 

Since you seem to be fairly familiar with tools, you could pull yours. I've tested mine by pulling it and placing it in boiling water and checking the resistance (ohms) through the connector. You can do it on the bike with a heat gun, but I personally hate putting a heat gun on motor parts. But that's just me. I've also done it that way, though, when feeling lazy.

 

With the ohmmeter on the plug and the coil heating up, you'll slowly see the numbers climbing. If it suddenly jumps to 0 or 1, that's your problem.

 

Hope that helps.

 

 

 

 

 

[DemonRanger]

10 hours ago, Bron-Yr-Aur said:

I'm shocked at how many of these threads I see, yet rarely do people mention the pickup coil. So many people start jumping to the worst case scenario (CDI) even though they rarely go. Same thing with the stator.

 

Your symptoms scream pickup coil to me. They crap out as the bike warms up and gets hot. (And the puddle sounds like a stuck or dirty float needle valve.)

 

Since you seem to be fairly familiar with tools, you could pull yours. I've tested mine by pulling it and placing it in boiling water and checking the resistance (ohms) through the connector. You can do it on the bike with a heat gun, but I personally hate putting a heat gun on motor parts. But that's just me. I've also done it that way, though, when feeling lazy.

 

With the ohmmeter on the plug and the coil heating up, you'll slowly see the numbers climbing. If it suddenly jumps to 0 or 1, that's your problem.

 

Hope that helps.

 

 

 

 

 

I appreciate the help guys , I will start a checklist and I won't rest until I figure this bike out. I don't mean to ask a stupid question but what are you referring to by saying pickup coil ? I'm familiar with most components like stator , cdi, rectifier , killswitch ,ignition coil . Thanks 

[DemonRanger]

Hi guys , so I'm starting to troubleshoot again from the top. I'm gonna work through every possibility.

tonight I stripped the bike down a bit.

1. stator tested good according to manual.

2. Tested ignition coil ( questionable ) according to the manual I should have 5.3  +\- ohms on the primary side, I got 7 ohms.  And on the secondary I can't get any reading. According to the manual I should get 12.6k ohms. I tested both ignition coils I have and I can't get a reading on either one. I'm pretty sure I'm doing it right, there's only a ground , a orange connector and the plug wire. It says  from the plug wire connector to the ground.  Maybe this is the fault ? I get spark with it installed in the bike? This is what it looks like. Also I noticed a tear in the boot for the plug, looks like it's just the outter rubber only. 

Edited June 3, 2017 by DemonRanger

[Bron-Yr-Aur]

You'll get a better reading by removing the plug cap from the wire. You re probably good on that though.

The pickup coil (some guys call it a crank position sensor) is the little magnet that senses when the crank is at top dead center (tdc) At tdc the little bump on the flywheel will be passing the pickup coil. That's how you set the air gap (usually at around .8-1 mm). There's an adjustment slot that allows movement of the pickup when the bolt is loosened. When the PUC craps out, the bike won't run. And this coil is more often the culprit for your problem than the stator (rarely) or cdi (even less likely). In fact, the pickup is the very first thing I would've checked, given your symptoms.

[DemonRanger]

4 minutes ago, Bron-Yr-Aur said:

You'll get a better reading by removing the plug cap from the wire. You re probably good on that though.

The pickup coil (some guys call it a crank position sensor) is the little magnet that senses when the crank is at top dead center (tdc) At tdc the little bump on the flywheel will be passing the pickup coil. That's how you set the air gap (usually at around .8-1 mm). There's an adjustment slot that allows movement of the pickup when the bolt is loosened. When the PUC craps out, the bike won't run. And this coil is more often the culprit for your problem than the stator (rarely) or cdi (even less likely). In fact, the pickup is the very first thing I would've checked, given your symptoms.

Ah perfect thanks I'll check this next. I know the sensor that you're talking about, when I had the stator off previously I remember seeing this. I will tackle this and update from there , thanks 

[DemonRanger]

Also dumb question , but is there a correlation between the woodrift key and TDC? If the key is at 12 o clock , doesn't that mean the piston is TDC? Just wondering to get a better understanding. Also for testing the gap I assume it's done using a feeler gauge ? Thanks 

[Bron-Yr-Aur]

No not necessarily. The woodruff key is just so the flywheel can remain constant. Its basically just making sure the flywheel doesn't move on the crank. And yes, when setting, loosen the adjustment bolt, insert the feeler gauge, press the coil to it, tighten bolt, remove feeler. That adjustment is a big deal by the way. Make sure its right.

I had a Triumph Bonneville. The factory spec changed only .2 mm from 1 to .8 because they were having problems with the bikes not running right at 1 mm.

[DemonRanger]

Update : so took the stator off the bike that was in it, noticed a lot of corrosion in there , everything was coated in light surface rust. I seen the pickup coil again and noticed its wore down and rusted. So I tested the pick up coil according to the manual. I can't get a reading on my meter! I think we may have a culprit. I verified by rechecking my other stator I have as a spare ( the one with damaged main windings ) and I got 240 ohms which is good according to the manual. 

The pickup coil in the bike won't give me any resistance readings , nor continuity, therefore I think it's gone!