2015 CRF250 misfire.

gharmon
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gharmon
Edited Date/Time 2/25/2016 8:50am
I just rebuilt my sons 15 CRF 250. Using OEM Honda parts I did a complete top and bottom end. I just finished buttoning it back up this AM. He said it rode fine for about three laps then started cutting out coming out of a turn. He said it you keep it WOT long enough (like on a straight section of track) it will smooth out. Obviously, we don't want it cutting out on the face of a jump so looking for some ideas.

This was my first FI rebuild and I must say that getting to the air box/throttle body/wiring, etc is a much larger chore compared to the carb versions. Looking for some ideas to try. He said that when it cools down it doesn't skip but as soon as it's warm again it goes right back to skipping. I told him to look at the air temp sensor on the air box and he said it looked fine. Also the code light wasn't showing anything either.

Also mentioned that after it's warmed up it wants to die when you pull in the clutch. If you pull out the choke he said this helps it a little. Any ideas guys? He's looking to ride tomorrow so I want to try and get this solved this evening.

Thanks

Gerald
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Paw Paw 271
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Paw Paw 271 2/20/2016 11:31am
2/20/2016 11:31am
Dirty injector, dirty fuel filter, OHM readings on coil out of spec or faulty fuel pump.

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slipdog
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slipdog 2/20/2016 12:39pm
2/20/2016 12:39pm
Good when cold and bad when hot usually indicated electrical. As usual Paw Paw is pointing you in the right direction as it's also possible that if you didn't plug the disconnected lines some dirt could have gotten into the FI system.
gharmon
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gharmon 2/20/2016 12:50pm
2/20/2016 12:50pm
slipdog wrote:
Good when cold and bad when hot usually indicated electrical. As usual Paw Paw is pointing you in the right direction as it's also possible that...
Good when cold and bad when hot usually indicated electrical. As usual Paw Paw is pointing you in the right direction as it's also possible that if you didn't plug the disconnected lines some dirt could have gotten into the FI system.
Yeah that's what I was thinking. The fuel line was total off the bike lying on the not-so-clean work bench.. The fact that it runs better with choke on indicates it needs more fuel correct?

He also mentioned that the engine felt "hotter than usual. Like the kick starter was actually hot to touch. I know if timing is off it can cause this type things but the timing was right. I checked and double checked plus it ran fine for a few minutes before acting up plus it was cranking fine (until it got warmed up).
Cmiller493
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Cmiller493 2/21/2016 6:28pm
2/21/2016 6:28pm
I would pull the fuel pump out of the tank and check the fuel filter. Somewhat common for the honda filters to get dirty and definitely will cause an issue. Just be careful pulling it out as there is a plunger in there that will get caught if you don't pull it out at the right angle.

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motosicko
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motosicko 2/21/2016 8:56pm
2/21/2016 8:56pm
Try turning up the idle to +2000 RPM first. Mine acts all kind of crazy below that.
FGR01
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FGR01 2/22/2016 11:26am
2/22/2016 11:26am
yeah, sounds like you're running lean if it's getting crazy hot and wanting the choke. I'd be checking the pump and the injector and looking for air leaks anywhere. Maybe the throttle body is not seated in the boots correctly or the clamps are loose. Or maybe the airfilter is not seated correctly.
gharmon
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gharmon 2/24/2016 1:40pm
2/24/2016 1:40pm
FGR01 wrote:
yeah, sounds like you're running lean if it's getting crazy hot and wanting the choke. I'd be checking the pump and the injector and looking for...
yeah, sounds like you're running lean if it's getting crazy hot and wanting the choke. I'd be checking the pump and the injector and looking for air leaks anywhere. Maybe the throttle body is not seated in the boots correctly or the clamps are loose. Or maybe the airfilter is not seated correctly.
Okay, after he brought the bike back home the other day I took the tank and stuff off to have a look see. I pulled the fuel line back off just to make sure no trash and checked all the electrical fittings. Took off every connection that I had undone and checked for trash. Everything looked fine. I also made sure the air boot and all associated connections were right and they were.

The engine isn't getting any hotter than before. So we can rule that out. We cranked it up and just like he said he was sputtering around the midrange area but would smooth out on a long section of straight (our neighborhood road). After several trips up and down the street that day it seemed to solve its own problem (never a good thing).

We put the bike away and today we tried it out again. This time it appears that the rough patch of throttle is more off idle than midrange now. Midrange up to WOT is good. I assume it's running lean but what do I know. Do these thing get much trash in them for real. Is the filter in the tank? Do they have a sock/filter on them kinda like car in tank pump/filter does? We have a 2010 and it had it's tank off several times and never seemed to be an issue. He may post the video he made today of the bike running.

Any help would be appreciated guys. Thanks.
nascarnate326 2/24/2016 3:10pm
2/24/2016 3:10pm
I believe there is a filter in the take. If the tanks off it comes out the bottom of the take. May be time for a new filter.

How many hours are on the bike?
MxMobster471 2/24/2016 3:50pm
2/24/2016 3:50pm
Here is a link to a short YouTube clip of what we are dealing with here.

https://youtu.be/EwPg45U3Yb8

Nascarnate326 the bike itself has roughly 130 hours on it. Give or take a little.
Dtat720
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Dtat720 2/24/2016 4:32pm
2/24/2016 4:32pm
If its a 2010 and you havent replaced the fuel pump and filter with the 2011 stuff, that is your problem. 2010 stuff is garbage and does exactly what yours is doing. Fuel injector as well, it will leak and drip in the throttle body. Swap it all for 2011 stuff and your issues will go away
MxMobster471 2/24/2016 5:08pm
2/24/2016 5:08pm
The 2010 is my brothers bike which has had the tank pulled multiple times and no issues. That's what he was referencing in regards to the 2010 model. My 2015 is the bike in question. It developed these issues post rebuild.
FGR01
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FGR01 2/25/2016 6:01am
2/25/2016 6:01am
Yes, the fuel pump has a filter where it takes in fuel. Remove the pump assembly from the bottom of the tank and check the filter. When they get clogged with micro-shit from gas the bike will start sputtering and cutting out.

I run an additional sock filter in the filler neck of the tank on my CRF450. So essentially my fuel is getting filtered before it even gets to the pump filter. It's kind of a PITA because I have to pour the fuel in really slow but it beats having the bike cut out on a huge double like happened to my buddy.
nascarnate326 2/25/2016 8:38am
2/25/2016 8:38am
FGR01 wrote:
Yes, the fuel pump has a filter where it takes in fuel. Remove the pump assembly from the bottom of the tank and check the filter...
Yes, the fuel pump has a filter where it takes in fuel. Remove the pump assembly from the bottom of the tank and check the filter. When they get clogged with micro-shit from gas the bike will start sputtering and cutting out.

I run an additional sock filter in the filler neck of the tank on my CRF450. So essentially my fuel is getting filtered before it even gets to the pump filter. It's kind of a PITA because I have to pour the fuel in really slow but it beats having the bike cut out on a huge double like happened to my buddy.
Which sock filter do you have? I never thought it was needed but after seeing how picky these FI bikes are I want to pick one up. Pics would be great if you have them too.
FGR01
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FGR01 2/25/2016 8:50am
2/25/2016 8:50am
nascarnate326 wrote:
Which sock filter do you have? I never thought it was needed but after seeing how picky these FI bikes are I want to pick one...
Which sock filter do you have? I never thought it was needed but after seeing how picky these FI bikes are I want to pick one up. Pics would be great if you have them too.
I have the Splitstream brand filter bought from Motostuff.com but there are other companies making them. Twin Air and I'm not sure who else.

http://motocrossactionmag.com/news/mxa-team-tested-splitstream-fuel-fil…

MXA says they didn't have to pour the fuel any slower. I call massive BS on that one. I have to pour very slow. The fuel actually flows through the filter mesh very fast but the filter ring fits so snug in the neck of the tank that it can't vent fast enough to allow the displaced air to escape. It's only got these 2 little gaps to allow venting. It's a compromise because if they put more/bigger gaps then in theory dirt could bypass the filter.

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