2015 yz 250 odd problem

pete24
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pete24 8/10/2015 9:39am
8/10/2015 9:39am
throw away the vent tube spinelli, and run a straight hose
avidchimp
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avidchimp 8/10/2015 9:52am
8/10/2015 9:52am
yamirider287 wrote:
yes fuel is 110 octane with klotz r50 and we have checked through wiring harness tested wires to see if there was bad ground or connection...
yes fuel is 110 octane with klotz r50 and we have checked through wiring harness tested wires to see if there was bad ground or connection and everything checked out. And its never consistent . It will run horrible and then the next day it will start right up and run perfect.
Probably not the issue, but 110 is way too much for a stock 250. Cut it 50-50 with pump 92. It will be much easier to jet and run a lot cleaner...
sostoked
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sostoked 8/10/2015 9:56am
8/10/2015 9:56am
Bummer dude!

I have 25hrs on mine without a single issue.

Everyone has said it but it seems like a fuel or reed issue to me. Ive had provlems that are equally confusing; seems like the best way to figure it out is to just swap parts with someone who has a yz. Example swap carbs or reed blocks and see if there is any change.
yamirider287
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yamirider287 8/10/2015 10:24am
8/10/2015 10:24am
oldmotoyamaha14 wrote:
Make sure your gas cap is venting properly. A clogged vent can cause fuel starvation.
I was wondering about that. When im done it will sit there an whistle.

The Shop

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yamirider287
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yamirider287 8/10/2015 10:26am
8/10/2015 10:26am
yamirider287 wrote:
yes fuel is 110 octane with klotz r50 and we have checked through wiring harness tested wires to see if there was bad ground or connection...
yes fuel is 110 octane with klotz r50 and we have checked through wiring harness tested wires to see if there was bad ground or connection and everything checked out. And its never consistent . It will run horrible and then the next day it will start right up and run perfect.
avidchimp wrote:
Probably not the issue, but 110 is way too much for a stock 250. Cut it 50-50 with pump 92. It will be much easier to...
Probably not the issue, but 110 is way too much for a stock 250. Cut it 50-50 with pump 92. It will be much easier to jet and run a lot cleaner...
I do 2 gallons of 110 and 3 of 91 pump
nytsmaC
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nytsmaC 8/10/2015 10:48am
8/10/2015 10:48am
oldmotoyamaha14 wrote:
Make sure your gas cap is venting properly. A clogged vent can cause fuel starvation.
yamirider287 wrote:
I was wondering about that. When im done it will sit there an whistle.
What is whistling, your gas cap vent tube? Remove the tube and test, if that doesn't fix it replace your gas cap.
Mr. Robinson 8/10/2015 3:01pm
8/10/2015 3:01pm
pete24 wrote:
throw away the vent tube spinelli, and run a straight hose
That's what I did. Don't like going from a gravity feed carb to a pressure feed carb because the tank can't vent.
Nik.M
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Nik.M 8/11/2015 7:54am
8/11/2015 7:54am
I had a simular problem on our 2014 yz 250s at about the same time frame. I found corrosion in the 6 pin plug that is behind the left hand radiator (goes from the stator to the cdi plug). Same centre pin corroded both times, cleanded it up and packed it with dielectric grease and the problem was gone. Have had 3 2015 yz 250s and took that plug apart before any were ridden and treated with dielectric grease and haven't had any issuses so far. While i was at it i greased all the other plugs aswell.
CamP
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CamP 8/11/2015 8:03am
8/11/2015 8:03am
Pressure washers and electronics don't mix well.
jerry atrick moto 8/11/2015 12:00pm
8/11/2015 12:00pm Edited Date/Time 8/11/2015 12:12pm
edit someone beat me to the gas cap vent. How about fuel supply to the carb? I know its a 2015 but could it have something in the tank floating around blocking the stand pipe in the fuel valve?
klein8
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klein8 8/11/2015 9:55pm
8/11/2015 9:55pm
Had a local rider here with a similar problem. Ended up being a torn seal on the injector. Installed incorrectly at the factory. Easy to check.
sostoked
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sostoked 8/11/2015 10:00pm
8/11/2015 10:00pm
klein8 wrote:
Had a local rider here with a similar problem. Ended up being a torn seal on the injector. Installed incorrectly at the factory. Easy to check.
this is a 2 stroke thread. not sure what this "injector" thing is you speak of?
NZ272
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NZ272 8/12/2015 12:52am
8/12/2015 12:52am
Bet it's the cap vent. If it's whistling its sucking air back in after you ride. Intermittent problem may be due to the level of gas you have in the tank when you start riding. Had this problem on my old 4t. Chuck the vent and go to a hose. My 2c
ehr400
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ehr400 8/12/2015 3:19am
8/12/2015 3:19am
Have you checked the timing? YZ's have had a long running variation in timing from the factory. I have had 3 of them and all had different timing from the factory. some 1.5 degrees advanced and one a degree retarded.

Caseclosed713 8/12/2015 10:02am
8/12/2015 10:02am
You have a weird problem to diagnose...probably something simple and stupid. I would start by making sure the tank and carb vent tubes are clean and venting properly. I had a similar issue with a street bike and one day it acted up so I popped the gas cap off and bingo, found my problem. I would also replace the spark plug because its a cheap and easy thing to rule out. I dont believe its jetting because it wouldnt run fine all day then all of a sudden run like crap unless theres a piece of dirt floating around that wont blow out. Electrical issues suck to diagnose especially when they only act up sometimes and just dont completely fail so I would start small.
Spagina767
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Spagina767 8/12/2015 10:16am
8/12/2015 10:16am
+1 on the gas cap vent. I had a YZ 125 back in the day that bogged to hell. Realized the small 1-way valve in the Yamaha tube was backwards, arrow pointing away from tank. Flipped it around, ran great.

If the tank doesn't vent, the bike runs like crap.

Pit Row

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Madc32
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Madc32 8/12/2015 11:33am
8/12/2015 11:33am
themrtoad wrote:
Sounds like water in the fuel to me
yamirider287 wrote:
My sister has a 14 ktm 125 and we run the same gas can and everything an she has no problems.
Not possible. Everyone knows that KTM's are lemons compared to Yamaha's.Laughing
Jaybird67k
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Jaybird67k 8/12/2015 11:56am
8/12/2015 11:56am
ehr400 wrote:
Have you checked the timing? YZ's have had a long running variation in timing from the factory. I have had 3 of them and all had...
Have you checked the timing? YZ's have had a long running variation in timing from the factory. I have had 3 of them and all had different timing from the factory. some 1.5 degrees advanced and one a degree retarded.

Yes, they have had this timing issue for sometime and it will make it pre detonate.
I machined a tool for my YZ 250 that threads into the spark plug hole with an indicator on it so I can positively verify TDC and then retarded my timing so I can run pump gas because the timing was off from the factory.
The 125's didn't have this problem.

I don't think this is the problem here.

Jason
dirtsquid
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dirtsquid 8/12/2015 1:58pm
8/12/2015 1:58pm
I have a 15 yz250 also, mine does that sometimes and I found that it was the gas. I use vp 110 and it started to boil. Mixing 50\50 helped.
rcannon
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rcannon 8/12/2015 3:18pm
8/12/2015 3:18pm
I like moisture under the ignition cover. Do you powerwash the bike? The covers are vented. Thats awesome, until a power washer hits it.

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