2015 YZ250F PROBLEMS!

braaap_man
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braaap_man
Edited Date/Time 7/13/2020 7:36am
Hey y’all, I have a ‘15 250F that I recently bought from a guy in CA, tested it out and it had about 10 hours on the bike. I’m a desert guy and tend to be pushing the bikes a little harder than usual, this is my first EFI bike ever. About 30 minutes into a “moto” it starts to die, bog, and backfire all at the same time. Took it back to the van and did some cleaning filter-wise, checked the fuel pump, and changed the spark plug. Worked great for about 15 minutes and then gives me small hiccups here and there but won’t die. Since then it’s had about 8 hours put into it and we replaced the pump, same deal, runs great now while it runs but now it won’t idle and has some first half throttle bog (only on 1st gear) and backfires every now and then. We’ve been told it could be a faulty TPS, pressure sensor, fuel pump, or dirty injector...anyone ever had this problem before? Really sucks I can’t trust my new EFI that’s loaded on aftermarket parts Sad If anyone has leads that could help let me know! I’d appreciate it, here’s the bike for attention.
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braaap_man
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braaap_man 7/8/2020 12:54pm
7/8/2020 12:54pm
braaap_man wrote:
Hey y’all, I have a ‘15 250F that I recently bought from a guy in CA, tested it out and it had about 10 hours on...
Hey y’all, I have a ‘15 250F that I recently bought from a guy in CA, tested it out and it had about 10 hours on the bike. I’m a desert guy and tend to be pushing the bikes a little harder than usual, this is my first EFI bike ever. About 30 minutes into a “moto” it starts to die, bog, and backfire all at the same time. Took it back to the van and did some cleaning filter-wise, checked the fuel pump, and changed the spark plug. Worked great for about 15 minutes and then gives me small hiccups here and there but won’t die. Since then it’s had about 8 hours put into it and we replaced the pump, same deal, runs great now while it runs but now it won’t idle and has some first half throttle bog (only on 1st gear) and backfires every now and then. We’ve been told it could be a faulty TPS, pressure sensor, fuel pump, or dirty injector...anyone ever had this problem before? Really sucks I can’t trust my new EFI that’s loaded on aftermarket parts Sad If anyone has leads that could help let me know! I’d appreciate it, here’s the bike for attention.

Factor E
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Factor E 7/8/2020 12:56pm
7/8/2020 12:56pm
Ck spark plug cap buy a hold down for it or maybe bad coil
braaap_man
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braaap_man 7/8/2020 1:22pm
7/8/2020 1:22pm
Factor E wrote:
Ck spark plug cap buy a hold down for it or maybe bad coil
We have the Twisted Development cap for the spark plug...we haven’t tried the coil yet so I’ll give that a try.
Zycki11
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Zycki11 7/8/2020 4:20pm
7/8/2020 4:20pm
Does this happen every time after washing the bike say the night before? Or are you running it dirty?

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braaap_man
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braaap_man 7/8/2020 5:02pm
7/8/2020 5:02pm
Factor E wrote:
Ck spark plug cap buy a hold down for it or maybe bad coil
Spark plug cap and coil are both in spec...moving onto the throttle body area now 🙃
braaap_man
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braaap_man 7/8/2020 5:04pm
7/8/2020 5:04pm
Zycki11 wrote:
Does this happen every time after washing the bike say the night before? Or are you running it dirty?
Washing the bike really doesn’t affect it at all, I always run it for a couple minutes after and all the plugs are waterproofed...I never run my bike dirty unless I’m out at a track or the desert so no to the last part
BRX-WRX
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BRX-WRX 7/8/2020 8:08pm
7/8/2020 8:08pm
Kinda sounds like a fuel tank vent not venting ? If it runs good for awhile before it starts acting up that should eliminate the injector and TPS.. Water in tank could possibly cause similar ?
braaap_man
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braaap_man 7/8/2020 8:32pm
7/8/2020 8:32pm
BRX-WRX wrote:
Kinda sounds like a fuel tank vent not venting ? If it runs good for awhile before it starts acting up that should eliminate the injector...
Kinda sounds like a fuel tank vent not venting ? If it runs good for awhile before it starts acting up that should eliminate the injector and TPS.. Water in tank could possibly cause similar ?
ironically we just checked that about 5 minutes before you posted, it’s venting, we know for sure there’s not water. Running problems are now fixed, it runs perfectly on the gas but won’t idle for long...we didn’t clean the injector since it got dark quick at home but were able to test the air pressure sensor...nothing unusual at all. Starting to think the TPS could be bad
Factor E
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Factor E 7/8/2020 8:50pm
7/8/2020 8:50pm
ck all wiring and connectors
sensor in air box
braaap_man
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braaap_man 7/8/2020 9:03pm
7/8/2020 9:03pm
Factor E wrote:
ck all wiring and connectors
sensor in air box
i’ll report back tomorrow, we just did the fuel pump connector, ig coil connector, and TPS connection. I’ll do the rest tomorrow 🤘🏽
BRX-WRX
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BRX-WRX 7/8/2020 11:46pm
7/8/2020 11:46pm Edited Date/Time 7/9/2020 12:15am
May sound silly, but did you blow & suck on hose before removal? the way the hose fits thru the holes in plastics could/can kink just enough to pinch. I have worked on a few with stock plastics & Cycra and a carbon kit.They all had routing bends. You can hear a gasp for air when removing gas cap when it dies to check ? I had a 2017 a couple months ago that left race gas in it for a couple months and it plugged the injector. Cool thing on the downdraft intake is you can remove a few parts to see the if injector is spraying correctly by eye sight ( wear a shield to protect YOUR EYES and face from back fire !)
Zycki11
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Zycki11 7/13/2020 7:36am
7/13/2020 7:36am
Those Yamahas had issues with electrical connectors getting water in them and causing the exact symptoms. Reconnect them a dude dielectric grease
kb228
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kb228 7/13/2020 7:58am
7/13/2020 7:58am
Id be looking at the injector and cleaning all of your electrical connections and applying dielectric grease.

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