06 Bruin YFM350 15-amp ignition fuse keeps blowing.
 

06 Bruin YFM350 15-amp ignition fuse keeps blowing.

Purchased the bike (As I call ATV's) about 2 weeks ago. Had to order brake parts as complete brake system was toast.
Until today, bike had been ridden 4 or 5 times for 5 to 8 minutes each.

My wife and I decided to take the Timberwolf and Bruin for a ride through the woods today and all was going well. I crossed a narrow stream, only 5 or so inches deep. No biggie. Then I came upon a mud hole and went through it with no issues. It was a bit deeper and I did have to spin my wheels to get through it.

About 7 to 10 minutes later, bike just died. No electrical at all. Had my wife go home and get our tow rope and I got it home.

Problem:

Blows 15-amp ignition fuse when key switch is turned on. (after handlebar power switch is turned on)
Tested new key switch. OK
Unplugged key switch from harness and jumped at bike end of connector. Same problem.
Unplugged both head lights, same problem.

I know there is a short somewhere but I wanted to see if there were any “under seat components that I should check first (and how) before I take the front top off so I can more easily get to the front-end wiring. I do have a multimeter.

Flowchart type advice would be a big help and much appreciated.

Thank you,
John

Without a wiring diagram it is difficult to be specific. Once the fault is further than the ignition switch it can be difficult, as the "live" branches out. I would disconnect the plug that goes to the CDI if the fuse stays intact you have narrowed it down to that. If it isn't the CDI, try disconnecting the handlebar lighting switch plug. To avoid keeping blowing fuses whilst testing, I tend to put a fairly high wattage 12v lamp across, instead of the fuse. If it glows brightly the fault is on, if it dims or goes out the fault is off.

Hi MerryMan...

Thank you for the reply and tips. Since you don't have one, I am putting a link here for the Yamaha Service manual. (or for anyone whom may need it) Top of PDF is the 400 and the second half is the 350.

Maybe you can decipher it. I get a bit confused looking at it.

BTW... My CDI has 3 plugs going to it. I'll just unplug them all and reconnect one at a time after each test. I have some halogen auto head lamps somewhere, so I will make a tester. Good tip and yes, I'm tired of blowing fuses while testing. lol...

https://gowebmastergo.com/bruin-350.pdf
This is on MY server so it's not going anywhere.


Thank you again,
John

PS - Can you tell me what all the different letters AFTER the 350 would mean? Like 350FAS, 350A, 350D and so on.

Well...

I don't know what has happened now.

I pulled the tank to start checking wires and once off I found a few more connectors so I checked them. All seemed OK. So, I had my fuse box test light hooked up and I checked it and the light did not light up. So I put a fuse in it and it started right up. As I was only running on the gas in the bowl, I shut it down. Now (I thought) I had a place to start checking wires.

Hooked my test light back up and tested it again to have a "go to go" starting point. Still did not show a direct short, BUT... now the light comes on when I push the start button. Crap. Back to square one, or worse.

-Square one. Took all tape off on the right side and inspected all wires. All seemed OK there. But I have not checked under the carb and from there back on the left side.

Note: Starter solenoid vibrates and makes a slight buzzing/humming noise when pushing the start button.

So, I'm taking a break right now and waiting for the charger to finish. Just in case there was not enough current to drive the starter. Doubt it but a good charge couldn’t hurt anyway.

Oh yeah... Almost forgot. On the ground wire connector on the main harness, with switches off and connector disconnected, I read 10.5 volts on the side going towards the front of bike. I'm pretty sure that's not right! Other side just goes straight to motor ground.


Thanks,
John

The lamp is only for testing, once you put power through it, it will glow brighter and probably has enough resistance to prevent the solenoid from going in properly. If the earth has power going to it, there must be a current leak somewhere, odd that the other earth lead doesn't show it.

Thanks for the manual, we are a repair shop, mostly selling/servicing/repairing Hondas and Suzukis, so have the manuals for them, but the odd Yamaha, Kawasaki and Can-Am does come in, so handy to have info about them. As I expected, the drawing shows lots of wires branching off after the ignition fuse, CDI, dash lamps, fan motor, etc, if the fault does come back on, you just have to isolate each circuit in turn until you find which one has the fault. I have, on occasion, found shorts by noticing a tiny wisp of smoke, wires tend to get hot at the point of the short and melt the insulation.