At Wits End! 2000 YFM250 Bear Tracker Will NOT Start! - ANY and ALL Help/Advice MUCH Appreciated!

[Savage3]

Do you have a spare CDI that ya can try?

Maybe it's not releasing at the proper time?

Can you test the input and output at cdi?

Can you test the trigger coil as well?

[rebeltaz]

13 minutes ago, Mech said:

Ha.. I'm a mech too Rebel and I know what it can be like.. and as has been said, and you know, it's sometimes the simplest thing. You certainly thorough, and methodical.. 

Check if there's a starter feed into the cdi unit.. 

 

12 minutes ago, Savage3 said:

Do you have a spare CDI that ya can try?

Maybe it's not releasing at the proper time?

Can you test the input and output at cdi?

Can you test the trigger coil as well?

I can, and I will check those tomorrow. 

[Savage3]

This is a tough one Boss, you're getting spark, but, not enough or not at the right time. You have a gremlin somewhere in that ignition system. I'd methodically check each component and narrow it down through process of elimination.  I keep a couple CDI'S and trigger coils on the shelf to save time. Ya never know, could be a problem none of us have seen. I've had them test good on a static resistance test and turned out to be bad.

[Savage3]

10 hours ago, Mech said:

i just had a look at the wiring circuits of a couple of yfm250/350 manuals I have, older models though, and they both have a power feed into the cdi when the starter's being operated. 

On a car they feed starter signal into the ecu because the timing pickups and airflow sensors aren't accurate at cranking revs, so the starter signal sets the timing fixed at a suitable point for starting.

On that thing, it could be either providing power to charge the capacitor, or to alter the timing.. If it has a feed from the starting circuit. Probably worth checking that signal's getting in there if it has it.

I agree, definitely worth checking!👍

[jcyoungkeit]

what compression in psi are you getting. could be not quite enough. engines need proper compression, fuel, spark, and timing.

[rebeltaz]

2 hours ago, jcyoungkeit said:

what compression in psi are you getting. could be not quite enough. engines need proper compression, fuel, spark, and timing.

over 150psi... according to the specs, that's correct.

[Savage3]

How did you make out with CDI, coil, and trigger tests?

[rebeltaz]

47 minutes ago, Savage3 said:

How did you make out with CDI, coil, and trigger tests?

Believe it or not, sidetracked on two more timing issues this past week! I got those straightened out, though, so I'll get back to this one this week. It's never ending around here... 

[Savage3]

Check that trigger coil Boss.....very important! Even if it's brand new.....

[rebeltaz]

6 hours ago, Savage3 said:

Check that trigger coil Boss.....very important! Even if it's brand new.....

I did. According to the meter/peak-adapter, it's putting out the 5+v as per the service manual.

 

This think fired off out of the blue the other day and ran like a champ for about 10 minutes. without me doing ANYTHING! The shop was getting smoked out and it was quitting time anyway, so I shut it down with the idea I'd roll it outside and start it back up when I came back. Yeah... that was the one and ONLY time it started. The customer has decided to not go any further so I guess this is one mystery that will not be solved

 

I appreciate all of the help and advice, though.

[Savage3]

There is the issue sir, I generally see about about a half volt AC or less when testing a trigger coil. If the CDI doesn't receive the proper signal at the proper time, it will generally cause ignition issues.

[rebeltaz]

20 minutes ago, Savage3 said:

There is the issue sir, I generally see about about a half volt AC or less when testing a trigger coil. If the CDI doesn't receive the proper signal at the proper time, it will generally cause ignition issues.

You're right... That was another POS I was working on. This one, the pickup coil resistance reads about 212, within range of the 189~ 231 Ω at 20 ̊C (68 ̊F) quoted in the manual.

 

These things are all starting to run together!

[Savage3]

34 minutes ago, rebeltaz said:

You're right... That was another POS I was working on. This one, the pickup coil resistance reads about 212, within range of the 189~ 231 Ω at 20 ̊C (68 ̊F) quoted in the manual.

 

These things are all starting to run together!

Yeah, they all seem to blend together. I know the feeling!

[Mech]

11 hours ago, rebeltaz said:

I did. According to the meter/peak-adapter, it's putting out the 5+v as per the service manual.

 

This think fired off out of the blue the other day and ran like a champ for about 10 minutes. without me doing ANYTHING! The shop was getting smoked out and it was quitting time anyway, so I shut it down with the idea I'd roll it outside and start it back up when I came back. Yeah... that was the one and ONLY time it started. The customer has decided to not go any further so I guess this is one mystery that will not be solved

 

I appreciate all of the help and advice, though.

Bummer. I hate that.. when you don't get to the bottom of it and the customer calls time.. I hate it so much I mostly try to convince them to leave it with me and I'll try in my own time..

Bad wiring I reckon, you moved some wire somewhere and it ran then vibrated out of place again....

 

Go on... have another look..

 

You know you want to....

[rebeltaz]

1 minute ago, Mech said:

Bummer. I hate that.. when you don't get to the bottom of it and the customer calls time.. I hate it so much I mostly try to convince them to leave it with me and I'll try in my own time..

Bad wiring I reckon, you moved some wire somewhere and it ran then vibrated out of place again....

 

Go on... have another look..

 

You know you want to....

lol... you're right. I do want to. 

I tend to not charge customers if I can't fix something - no matter how much time I've got in it - unless it's for parts that I can't take back out or when I do repair what it was brought in for only to find deeper issues later. As it is, they owe me about $400 for this ... thing...  I will be surprised if they actually come get it. If I do get stuck with, you can bet that I will be getting to the bottom of this and I will definitely report back if that happens!

[Mech]

That sounds like the good ethics mate...  That's my policy too..  If I can't don't fix it, it's no charge, not for the labor anyway.. Parts as you say, needed to eliminate well diagnosed possibilities I have always discussed and negotiated before trying them..

 

The whole of being professional, is inspiring trust and confidence in your customers.

[rebeltaz]

On 2/13/2022 at 4:47 PM, Mech said:

I'm about out of ideas for you. Compression, fuel and properly timed spark.

So no backfiring, no smell of burnt fuel, dry plug.. all I can think of is that it's not drawing fuel in..  Blocked exhaust..  You'd think it would be in the muffler, but perhaps the header's double walled and it's collapsed the inner or something highly unusual.

Disconnected the exhaust at the head. I don't know... It has to be something intermittent, but I can't find it. If the customer winds up not picking this up, I WILL find it, though. And I will be sure to report back here. I appreciate EVERYONE'S help.!

On 2/13/2022 at 4:55 PM, Mech said:

I wonder if there's something in the bottom of the plug hole preventing the mix getting to the plug... mud maybe, cobweb of soot.... Never seen it but...

It's strange that fuel down the plug hole didn't even get it to kick. No air or no  ignition of the mix.

I even took a camera and snaked it down the plug hole. All good...