MarkinAR

Honda 300 Fourtrax.

Your guess is as good as mine on wiring.  I usually scour the interwebs and look for a wiring diagram then get to color mapping everything.  I have no experience on Polaris machines.

I wouldn't try it either, i'd hate for 2 wires to be crossed in the plug and burn your good one.  Check ebay, I bet there's a good used one out there.

There is some danger in replacing parts, especially if they are chinese knock offs.  Does that one have a regulator/rectifier?  That would be my first suspicion, bet it's not putting out over 12V.

That one had front hydraulic drums, right?  Been a while since I was in to one of those.  If the handle is stiff and not providing any braking I'd suspect the wheel cylinders are partially seized.  If it were a squishy handle I'd suspect the master cylinder o-rings were bad.

@DaleS Glad you found the forum helpful.  I'm a member of several and this is by far the best to throw random questions to as there are many different machines represented here.

Welcome to the forum!

Ha, that response sounds like something I would say.

so yes, most likely just flooding itself to death.  I'm assuming by aftermarket carb you mean a chinese clone?  The jets on those are NOTORIOUS for not being stamped, stamped wrong, way wrong size, just junk in general.  I've used a few out of necessity and they either fire right up or you spend time tinkering to get them to 80%.  Do you have the OEM?  If you do use the original jets in the clone carb, that works sometimes.  I've also had the clone carbs come in with the float terribly high or low, give that a check also.

Your situation reminds me of a clone carb on a ATC 185s I had a while back.  Couldn't get that thing to run for anything if you stabbed the throttle.  This issue was the carb passages were wrong not just the jets.  I ended up putting a small main jet and raising the needle a clip or two and got it to about 90%.  Good enough to pop wheelies non stop because that's what 3 wheelers are for!

Was there no spark?  Curious why you replaced so many parts.

They are different part numbers so there's a good chance they are different.  I think a lot of motor and trans stuff is the same but I'd bet electronics are different.

So black plug would be flooding which could be flooding or reducing spark.  Could be packed exhaust, needle valve and seat leaking, coil shutting down with heat, lot of options.

Could also be timing.  If the timing is off just right it'll fire on the exhaust stroke and seem to run when in fact it's really only exploding and not running correctly.

Check Babbitt's online or partzilla.  they have full diagrams so you can find what you need.

Easiest thing to check is trash in the main jet.

if it idles fine, then the idle circuit and low speed jet is clear.  if it bogs off idle that's when it's transitioning to the main jet.

Not much aftermarket support for that little engine.  Maybe there is enough wall to punch it and use a different piston from another motor?

Disconnecting the ground wire doesn't fix the issue, but will cause the electrical system to seek out another ground since that one is broken.  i'd bet it's a faulty plug, internally broken wire, or bad ground point that needs to be cleaned.  The worry with disconnecting a ground is that sends additional load to another ground, potentially burning the ground wire.

Blowing fuses nearly always will trace back to bare wire causing direct short or overcharging by the stator.  I'd trace the harness starting at the battery and going forward.  Almost guarantee somewhere there is a bare spot that touches metal occasionally.

P1619 is just related to oil change.  Looks like the throttle cable housing is just broke so i'm sure replacing the cable will resolve it.  But that's just a guess.

SunF makes a great knockoff of the big horns at a fraction of the price.  That tread pattern is one of the best all around performing tires out there. 

How is the battery?  Seems like some of the Yamaha's use the battery as a capacitor, essentially lowering the system voltage to 12ish volts.  Without a battery or with a bad battery it may be dumping 14-17V into the system and burning components.

If the battery isn't the issue then I'd shuck the plastics and start running down the wiring harness from the battery forwards.  It's either a jump in voltage or a direct short to ground that's burning the CDI.  Curious though why it wouldn't pop a fuse if it's a direct short...

There are really only 2 ways to toast a CDI and that's a bad regulator or direct short somewhere in the harness. 

Rick's CDI is the best for Honda by a mile, maybe google and see if there is one for yours? Otherwise good 2nd hand OEM from ebay or new if still available on Partzilla, Babbitts etc. The chinese cheap ones are just terrible. I've had good luck with good 2nd hand OEM parts on ebay. 

Most likely CDI.  Normally when you get spark when releasing the start button that's not actual spark but instead is residual voltage bleeding off from the starter circuit.  You can always try baking the CDI for 5 minutes or so at 250 and see if it'll start then.  CDI's usually go bad when the ceramic in the capacitor gets cracked and it gets a bit of moisture.  If it'll start after that, you know it's the CDI and time to get a new one.  Don't buy the cheap $30 chinesium one though, those are only about 2 out of 10 good new in box.

@Gary Korneman Makes a good point here.  I have seen a few ATV's that have a reverse rev limiter and sometimes that causes some really odd issues.  Might look into that and see if your machine had it and how to bypass it to rule it out.

If it's like the older big bear i had, there is a linkage adjustment on the shifter.  For some reason the shifter and clutch adjustment are on the left side on some Yamahas.  Might adjust the linkage so it's a bit tighter and see if that does it.  Then try clutch adjustment.  If all of the above fails, I'd lean towards a shifter fork worn smooth out and need replacing.

But this is all just guessing though to give you something to troubleshoot.

Can you push the shifter down and hold it and get it to disengage gear?  I had one do that once.  Never got into it though to work on it.  Ended up selling it as is.

basic motor parts are the same.