2015 YZ250F PROBLEMS!

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4/26/2015 12:27 PM

I bought my son a 2015 YZ250F in August of 2014. At 12 hours the bike started cutting out, snapping and popping, barely running. At first you could shut it down and restart it 15-20 times and it would clear up. It progressively got worse until eventually at round 20hrs it shut down and wouldn't start. Bike now has 55+hrs on it and probably 10+hours of that has been spent riding the bike around at a shop or just running trying to figure out what's wrong.

First Yamaha tech that worked on it at the Hog Haven Pro Shoot out last year, said it was a "fuel pump." Yes, that was the first big race we missed due to the bike. Put a NEW fuel pump, 20 mins later same problem. Bike has been to at least 2 different Yamaha dealers, most main electrical parts and has been swapped out. Even a new computer. Bike ran decent for about 8hrs until it would get wet on the track. My son has hit the same mud hole several times on a particular track and the bike would immediately shut down. Let it dry out and would crank, MOST of the time.... Not the spark plug cap problem either.



Just got the bike back from the shop after having a new top end installed. They supposedly replaced two sensors, finally it was running good. 1.20 hours later it is doing the same thing.



I ordered the same two new sensors from Rocky Mountain ATV a few days ago and had them overnighted. Installed new temp sensor and pressure sensor. Bike fired right up ran like a charm. 1.3 hrs later, bike has shut down again and would not crank.

Went to the track bike ran fine for a few laps. Bike shut off in mid air on my son TWICE. Even tired installing new kill switch, as a fellow YZ owner had the same problem and it seemed to cure his. Put it on and the bike ran great for just a few laps and shut off again. As of right now it will not crank. I can probably go to it tomorrow and it will run, for a few laps anyway....



I am at my wits end. I have tried not to post, hoping Yamaha would find the problem. After a ton of money thrown at a bike that hasn't ran right since 12 hours I have had it.


I know of at least 4 different 2015 YZ250F's that have had similar issues. No ways as bad as ours. We were at a small local race and there where 3 new YZF's were having the same issues at the same time. One had 2.2 hours on it... All of the others have cleared up without a repeat occurances as far as I know.



I can't help but think others are having problems and are just as lost as us.



Again we had a big race this weekend and my sons NEW bike wouldn't not run dependably... We have only had this bike make it through a few races. He wanted to make a run at Loretta's this year. Haven't had the bike running right long enough to try to qualify. It is really sad when you can't depend on a BRAND NEW BIKE and you see your sons heart broken race after race....

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/26/2015 12:53 PM

Well all i can say is that there has been many problems with the new generation yzf 250s, and i would not buy one.

I think you should get a new bike, at least here in Finland you would be able to get one from the importer if you have such massive problems with a new bike.

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4/26/2015 1:10 PM

Ok, it could be a couple of things....

Fuel starvation....Plugged fuel tank vent in the cap.
Vapor locking.....Put insulation under the fuel tank.


Coil breaking down due to heat.

Paw Paw

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4/26/2015 3:28 PM

The one consistent thing I notice is moisture bringing the probs on. Have you tried opening, cleaning and putting dielectric grease on every connector in the wiring harness? Check all connections and make sure all grounds are clean and tight. You may need to trace all wires and maybe even replace the wiring harness. It sounds like you've got an intermittent "open" or a wire rubbed bare somewhere causing a short.

If the bike is running good and you hose the bike down with water will it bring the prob on immediately?

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Powerband in every gear !

4/26/2015 5:12 PM

Most every pro team running Yamaha 250f's pulls the electrical harness "out" when pressure washing the bike. Local builder here installs new stator and pump, stator not sending steady voltage to pump. Pull all electrical contacts apart clean and protect, I'd use plenty of dialectic(sp) grease.

Another issue my neighbor has had was running MR12 in his 250f and now 450. I think it is a vapor lock issue running oxy fuel here in this heat. He ran pump gas and the bogging issue quit, VP also told him to try this to confirm. Like Paw Paw mentioned heat blanket under tank couldn't hurt either.

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4/26/2015 6:19 PM

Use should use U4.4 if it's 85 degrees or above. MR12 does not works well above 85.

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4/27/2015 7:49 AM

Jakes Dad wrote:

Most every pro team running Yamaha 250f's pulls the electrical harness "out" when pressure washing the bike. Local builder here installs new stator and pump, stator not sending steady voltage to pump. Pull all electrical contacts apart clean and protect, I'd use plenty of dialectic(sp) grease.

Another issue my neighbor has had was running MR12 in his 250f and now 450. I think it is a vapor lock issue running oxy fuel here in this heat. He ran pump gas and the bogging issue quit, VP also told him to try this to confirm. Like Paw Paw mentioned heat blanket under tank couldn't hurt either.

Thanks for all the responses.

Jakes Dad, that blows my mind that you would have to pull a harness to wash a dirtbike. Appreciate the info! I have been washing bikes with pressure for almost 30 years. Other than a seal or two I have never had a problem. If the bike can't stand water something is wrong. I bet you want see one of the Star Racing Yamaha's quit during a mud race this year at the Nationals. While my sons bike, prepped as they suggest, want make it 3 laps in the mud.........

The stator and pump have supposedly been replaced by Yamaha. I helped install the pump so I KNOW it was done.

The connections have been coated in d grease several times already.

Far as fuel I use high quality 93 octane that is no more than 5 days old. This thread is the first I have heard of vapor lock being an issue. I really don't feel this is the problem though. It seems to be an electrical issue.

Right on schedule I just went out and kicked the bike, 3rd kick it fired up and ran great. I am sure I could him on it for any where from 2 laps to about an hour and a half before the will die for the day....

Calling Yamaha when they open!

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/27/2015 8:58 AM

You need to look at vapor locking as it is a known issue.

Paw Paw

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4/27/2015 10:48 AM

Why vapor lock when the problem seems to come with water or mud?

I suspect a bad connection or short somewhere or some other electrical problem like a bad coil. I would be inspecting every millimeter of that wiring harness as a first step.

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Powerband in every gear !

4/27/2015 12:05 PM

Folks "feelings" seem to be getting in the way of finding and resolving the issue at hand, so I will bow out.
Good luck.

Paw Paw

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4/27/2015 1:49 PM

Paw Paw 271 wrote:

Folks "feelings" seem to be getting in the way of finding and resolving the issue at hand, so I will bow out.
Good luck.

Paw Paw

Wow. It appears to be your "feelings" that got hurt simply because someone else has an opinion to offer that differs from yours. That's too bad.

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Powerband in every gear !

4/28/2015 6:58 AM

Seen the same problem on a local bike turned out the water temp connector was fritzed and would make the bike run crazy rich or lean and not start be cause it was too lean. We thought we would have it fixed each time a new temp sensor was fitted because it would run good for a while. Grab a new harness and see what happens....

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4/28/2015 7:49 AM

I have a friend that had very similar problems out of a rmz450. After a bunch of wasted money he finally bought a new wiring harness and it fixed his

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4/28/2015 1:35 PM

I second Paw on the vapor lock, best friend had it happen to his yz450. It is also an easy problem to figure out, just replace the gas cap and hose with another to see if it works.

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4/28/2015 4:11 PM

New wiring harness ordered today.

Far as vapor lock, would removing the cap to check the fuel level correct that? Point being, it still does no matter fuel level or after checking level.

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/28/2015 7:22 PM

Fuel level does not matter. The lock happens when the vent in the gas cap gets stuck closed or the breather hose is plugged and does not allow air into the tank which causes a negative pressure, to the point that the pump cannot pump the fuel out of it. You can also tell when you remove the gas cap right after riding and you can hear the air being sucked into the fuel tank. May not be the answer to your problem, but then again it could be something this simple. Like I said, I have seen it before.
Good luck

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4/28/2015 8:51 PM

dereck519 wrote:

Fuel level does not matter. The lock happens when the vent in the gas cap gets stuck closed or the breather hose is plugged and does not allow air into the tank which causes a negative pressure, to the point that the pump cannot pump the fuel out of it. You can also tell when you remove the gas cap right after riding and you can hear the air being sucked into the fuel tank. May not be the answer to your problem, but then again it could be something this simple. Like I said, I have seen it before.
Good luck

You're confusing vapor lock with common failure to vent.

What you describe is failure to vent. If air can't get in the top, fuel can't get out the bottom because it's trapped by vacuum. Like when you hold your finger on top of a straw full of soda.

Vapor lock is when heat from the engine raises the temp of the underside of the tank, pump, and high pressure line to the injector to the point that the fuel boils. You then have air bubbles being delivered to the injector instead of a nice solid stream of fuel, causing momentary cutting out. This is why PawPaw suggested insulation under the tank and you see the Pros running the foil insulation under there.

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Powerband in every gear !

4/29/2015 5:34 AM

Thanks for the info everyone. I really hope we are narrowing down the possible causes! I am taking each post seriously!

I would assume that as soon as the fuel cools off it should go back to running normally, would I be correct?

If this is the case, I don't think this is our problem. Bike has sat for days with the same problem. It normally clears up after a few hours but no always.

Anyone have pics of the insulation on the bottom of the tanks? I would like to see exactly how to CORRECTLY do it.

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2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/29/2015 7:11 AM

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4/29/2015 7:15 AM

Interesting quote from MXA in that link, "Something that is never found on a local racer.s bike, but is used on every factory bike in the pits."

Does this really help the bikes performance or more of a preventitive mod?

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4/29/2015 7:53 AM
Edited Date/Time: 4/29/2015 7:55 AM

CarlinoJoeVideo wrote:

Interesting quote from MXA in that link, "Something that is never found on a local racer.s bike, but is used on every factory bike in the pits."

Does this really help the bikes performance or more of a preventitive mod?

It's more of a preventative mod. Fuel boiling can for sure happen, but it's not as big a problem in a closed high-pressure system like a dirt bike has unless you are running 30min+2 laps in 85deg. heat. The main benefit to a heat shield is to keep the fuel cooler and more dense, thus helping efficiency/power. Your kid's bike isn't boiling it's fuel in 2-3 laps of riding, it's an electrical problem.

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4/29/2015 9:25 AM

submit it for a "Lemon Law" replacement!

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4/29/2015 12:13 PM

I second that lemon law. Not sure if it can be done on a bike? My dad did it in a new Ford Explorer when I was kid...

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4/29/2015 3:01 PM

I had one come in to my shop with similar symptoms. 2014 model. Would run good for 10-15 minutes then would start bogging and running awful. Yamaha scanner had codes for TPS, Temp sensor, IAP sensor, ecu input voltage. Temp sensor and IAP sensor tested bad so we started with temp sensor... didn't work. Intake air pressure sensor fixed it. I removed, cleaned, and dielectric greased every plug on the bike. To my knowledge he has put 3 or 4 hours on it trouble free. His bike had about 40 hours

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4/30/2015 5:17 AM

There has been 2 or 3 air pressure sensors installed. Also, connections have been cleaned and dielectric greased several times already.

Hoping the new harness will be here today and by this weekend I will know whats going on. Got another big race this weekend. Hopefully we can keep him on the 250F! He rides schoolboy 1 on a YZ125 as well. Thank goodness we kept that bike or we would have missed most races since buying the 4stroke.... He managed to get 3rd overall in our fall series in 250C riding his 125 most of the races as the 250F wouldn't run right....

|

2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



4/30/2015 7:10 AM

sgrimmxdad wrote:

There has been 2 or 3 air pressure sensors installed. Also, connections have been cleaned and dielectric greased several times already.

Hoping the new harness will be here today and by this weekend I will know whats going on. Got another big race this weekend. Hopefully we can keep him on the 250F! He rides schoolboy 1 on a YZ125 as well. Thank goodness we kept that bike or we would have missed most races since buying the 4stroke.... He managed to get 3rd overall in our fall series in 250C riding his 125 most of the races as the 250F wouldn't run right....

Does the bike run good for awhile each time after installing the new IAP sensor?

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5/1/2015 4:36 AM

sgrimmxdad wrote:

There has been 2 or 3 air pressure sensors installed. Also, connections have been cleaned and dielectric greased several times already.

Hoping the new harness will be here today and by this weekend I will know whats going on. Got another big race this weekend. Hopefully we can keep him on the 250F! He rides schoolboy 1 on a YZ125 as well. Thank goodness we kept that bike or we would have missed most races since buying the 4stroke.... He managed to get 3rd overall in our fall series in 250C riding his 125 most of the races as the 250F wouldn't run right....

jsmx97 wrote:

Does the bike run good for awhile each time after installing the new IAP sensor?

Yes, but it runs fine after installing about any new sensor, for a while! Also ordered a rectifier! Going to install the harness first and go from there! Thanks again for all the replies!

|

2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



5/4/2015 7:49 AM

Well, brand new harness DID not fix the problem. It ran about 10 laps Saturday at practice and quit. Brought it home, it wouldn't start. Hope and figured it may make it through the race if we keep the laps down, if it would start the next morning. Well right on cue, it started and ran great. This time it only made it 3 laps in practice and hasn't started since. I haven't tried it this morning.

Don't know if it is normal but the stator side of the motor was scorching hot!! We thought the coolant must be low. I immediately popped the rad cap and it was properly filled and was cool enough to hold the cap. The other side was no ways as hot. SO we ordered ANOTHER stator right there on the spot, supposed to be here Tuesday.

My son wants to run a LLQ this weekend and I don't think the bike will make it Had to ride the old two stroke yesterday! Good thing I picked up a decent YZ250 smoker or we would be in bad shape. Blowed the fork seals out of that yesterday so tearing it down to send off.... It never ends LOL!

|

2020 YZ450F
2018 KTM 450SXF FE
2016 YZ250F 2008 CRF450R
2015 YZ250F 2008 CRF250R
2001 CR250R
2010 YZ250 2012 CRF150R
2009 YZ125 2010 KX109.5
SSR Motorsports Dealer
TAGMX Suspension & Graphics! www.tagmxsuspension.com https://www.liquidskinzdesign.com/



5/4/2015 8:23 AM

Man tough luck you have with this bike. Why is the Yamaha dealer not helping you out with a loaner 250F or something? The Yamaha dealers here in Holland are always pretty understanding in this sort of situations.

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5/5/2015 10:13 PM

Sorry to hear about all these problems, I feel like Yamaha should be helping you guys fix this problem. Really lame you have to basiclly replace every part on the bike until it's fixed...

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