2004 crf150f misfire

tyler_richard
Edited Date/Time 5/11/2016 2:56am
How's it going guys, just recently picked up this bike for my girl. The guy knew it had "carb" issues, I figured it was electrical because after I got it home, fired it up and took off in the back and it ran somewhat acceptably, then after about 10 minutes of hard riding on a 150, it ran very poorly. The mid to top rpm range sputters, no back fire. I have adjusted the air fuel mixture as suited and still the same issue persists, I ordered a new coil and spark plug wire thinking the coil may be bad and once it gets hot it is almost useless. Anyone got some suggestions or feedback for me? I'm just awaiting the coil to see if that fixes the problem.
Thanks
Tyler
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xnationalwrench 5/10/2016 6:29pm
5/10/2016 6:29pm
Any idea on how much time is on the bike? You should check the valves. When its hot do you have spark?
Paw Paw 271
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Paw Paw 271 5/10/2016 6:34pm
5/10/2016 6:34pm
Ok, your screw is a fuel screw.
If the bike set for a while, then I would do the following....
Check the carb float for leakage and or set at the correct height. Id either is off it can either flood or suffer from fuel starvation. If those are good then you may want to check the carb vent lines for dirt, trash of insect nest. This also goes for the fuel tank vent line. If any are plugged or reduced in air flow it will starve the engine for fuel and shut off after a few minutes of running time.
Another issue could be the ignition coil breaking down. The only way to be sure is to do an OHMS test on the primary and secondary sides of the coil. Rusty coil mounts can cause running issues as well as a dirty or rusted spark plug cap. Both will show up in the OHMS testing.
YOu may also want to check the fuel flow at the fuel tank petcock as there is a screen filter made into it that can clog and reduce fuel flow.
The next time this happens...Remove the fuel tank cap off for a second or 2 and then reinstall it. If it starts running better for a short time and then repeats the problem it's a fuel flow problem.

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tyler_richard 5/10/2016 7:32pm
5/10/2016 7:32pm
Occasionally fuel will randomly leak out the overflow, I forgot to mention that!
tyler_richard 5/10/2016 7:36pm
5/10/2016 7:36pm
And I will check the valve lash to be sure, old owner was a friend, he said he just put new piston, rings, and re seated the valves

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Paw Paw 271
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Paw Paw 271 5/10/2016 8:13pm
5/10/2016 8:13pm
Fuel out the over flow shows a leaking float valve or the float level is set too high. This will cause running issues.

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tyler_richard 5/10/2016 8:52pm
5/10/2016 8:52pm Edited Date/Time 5/10/2016 8:52pm
Valves are now set at proper distance...I set the float pretty low and it still leaks. How would I replace the float valve? Is it the little pin that seals gas flow as the float pushes into it as gas level rises?
Paw Paw 271
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Paw Paw 271 5/11/2016 2:56am
5/11/2016 2:56am
tyler_richard wrote:
Valves are now set at proper distance...I set the float pretty low and it still leaks. How would I replace the float valve? Is it the...
Valves are now set at proper distance...I set the float pretty low and it still leaks. How would I replace the float valve? Is it the little pin that seals gas flow as the float pushes into it as gas level rises?
Yes, and that part is available.

Paw Paw

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