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Lynch
4/18/2019 11:39 AM

Having some issues with my 50 hour old 2018 YZ450F, the bike suddenly shut off while riding as if I ran out of gas (it was full) and won't start.
I have managed to start it two times but both times it shut off after a few seconds, while it was on it ran fine. 
The times it doesn't start it just clicks, aka it's not turning over the starter/engine at all. 
Battery reads 13.29V however when you press the start button it jumps to 0.0000V, shortage of some sort? 

I have checked the two 15 fuses close to the battery but I will check more thoroughly tomorrow, I have another battery I can try. 

Any help or tips are much appreciated. 

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kb228
4/18/2019 12:24 PM

Classic case of a dead battery. The voltage drop tells you it fails the load test if tested at autozone for example.

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Lynch
4/18/2019 12:43 PM
kb228 wrote:

Classic case of a dead ...more

Makes sense but I thought it would still run with a dead battery and not shut it off? And find it odd that it started two times Will try tomorrow with another battery.

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Lynch
4/19/2019 4:39 AM

Got it started with another battery, runs fine for 20-30 seconds before it just shuts off

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Paw Paw 271
4/19/2019 5:29 AM

REplace battery with a good Li unit. Your battery has a loose plate and is shorting out with current flow.
Fuel pump is bad.

Paw Paw

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Lynch
4/19/2019 6:30 AM
Paw Paw 271 wrote:

REplace battery with a ...more

I have tried another battery and it starts fine, runs for a while then shuts off. I'm gonna see if it's the same fuel pump in the 250, if it is I can try changing tanks.

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Lynch
4/21/2019 4:59 AM

Update

I can get the engine started evertime (even with the old battery) if I turn the backwheel so the engine moves, if I don't do that it just clicks on the starter as if the top end is solid. It runs for longer now but sounds a bit weird (something I might not have noticed before since I rarely got it to start) My guess is that the decompression sensor is either faulty or something is wrong with the piston/top end. However I should get a fault code for the sensor and the engine shouldn't even start according to the manual.

Going to send a message to a few engine builders I know that might have experienced something like this before.

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nick610s
4/23/2019 7:58 AM

Starter clutch.. upgrade to the 2019 unit.

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Lynch
4/23/2019 8:04 AM
nick610s wrote:

Starter clutch.. upgrade ...more

Don't think so since I can get it started now but runs a bit iffy and shuts off.

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mxrider971
4/23/2019 8:51 AM

Check your kill switch.

Edit: Nevermind, I re-read everything and that wouldn’t be it.

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Jack_Wagon
4/23/2019 6:39 PM

Please update if you find a positive fix. My son's is doing something similar but not as frequently as yours. It's been a nightmare to diagnose since it only does it near the end of long motos.

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Lynch
4/23/2019 10:11 PM
Jack_Wagon wrote:

Please update if you find ...more

Absolutely! We have checked all the eletric bits and all checks out good so next step is to open the engine, it's due for a top end anyways.

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Jack_Wagon
4/24/2019 7:52 AM
nick610s wrote:

Starter clutch.. upgrade ...more

What are the symptoms of the starter clutch issues these bikes have? On other bikes I've seen when a starter clutch goes out the starter clutch just spins and doesn't engage to turn the motor. I guess it could have the opposite effect on these bikes and lock the motor to the starter?

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Jack_Wagon
4/24/2019 8:02 AM
Jack_Wagon wrote:

Please update if you find ...more

Lynch wrote:

Absolutely! We have ...more

The fact that you can turn the back wheel and get it to start tells me you definitely have an electrical issue. Does the fuel pump cycle when you turn the wheel before starting? I would check all your grounds, condenser, and your harness. The condenser is mounted very poorly. We move ours to subframe under the side cover. I've seen a few wiring harness go bad.

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Lynch
4/24/2019 8:12 AM
Jack_Wagon wrote:

The fact that you can turn ...more

Eletric wouldn't cause it to sound like it does currently I think my dad is tearing it down as we speak. I got another bike to ride so not rushing anything.

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nick610s
4/24/2019 9:31 PM

i have one other theory on this, my friend had an issue that the bike was run low on oil before he bought it 3 hours on the bike.. bought it used.. and it cooked the main bearings causing it to have a similar issue to what you’re having.. would turn over but slowly.. maybe you didn’t get a full oil change the last time it was ran hard and you are experiencing this as well. Thing only takes 690 cc’s at oil change, I just put 10 extra every time. I also run bel ray 15w50 full syn in mine.. 83 hours and it looked like new in side when I did my last top end.

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Talisker
4/25/2019 5:46 AM

If you have removed the fuel tank recently make sure the fuel line has not been twisted and pinched. This is very easy to do and is often overlooked.

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nick610s
4/25/2019 8:41 AM
nick610s wrote:

Starter clutch.. upgrade ...more

Jack_Wagon wrote:

What are the symptoms of ...more

Ive not experienced this myself but ive heard it can work both way.. starter clutch creates additional drag on the motor causing it to kill the battery quicker.. and it just goes out and wont engage.. I have 83 hours on my bike, original battery and starter clutch.. replaced top end @ 75.. zero issues.

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Lynch
4/25/2019 8:17 PM
Talisker wrote:

If you have removed the ...more

Not pinched, thanks for the tip!

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Lynch
4/28/2019 10:51 PM

Finally found the issue and it's gonna be a costly fix. What was supposed to be a quick top end/cam chain swap turned into removal of the engine.

Going to need at minimum new rod/rod bearings and main bearings. No idea how the hell they are shot in 50 hours, shit happens I guess. I do feel lucky at the moment that the rod never said peek-a-boo through the cases

Going to call a few engine builders and ask what could cause this, if there is an underlying issue I need to find it.
Also going to take a chance and call Yamaha about it.

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soggy
4/29/2019 7:21 AM

give derek harris a call.

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Titan777
4/29/2019 6:43 PM
Lynch wrote:

Finally found the issue ...more

There were no signs of it, no weird sounds / knocking, etc..?
Is there a way to know if you need a new rod before this happens, without tearing down to inspect it?

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Lynch
4/29/2019 9:36 PM
Titan777 wrote:

There were no signs of it, ...more

Nothing, ran perfect then just stopped.
I don't think so, you won't know until you stand there with the top end taken off. This isn't something that should happen in 50 hours or even 100 hours so I wouldn't worry about it if I were you.

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nick610s
4/30/2019 12:24 PM
Lynch wrote:

Finally found the issue ...more

Sounds like something similar to what I posted above. I would upgrade to the 19 starter clutch while you have it apart.. supposed to put less drag on the motor. It’s possoble that the clutch drag caused your motor to work harder in the 50 hours you owned it. Thereby putting extra strain on the components.. Also run better oil than yamalube. Not sure what you guys run but just a suggestion.. motul or belray etc.

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Titan777
4/30/2019 7:19 PM
Lynch wrote:

Finally found the issue ...more

nick610s wrote:

Sounds like something ...more

Not to cause an oil war but Castrol Power 1 Racing 10W50 (or 40) is one of the best oils you can get.

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