Question about 2004 Yamaha DT 125 R

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I have a Yamaha dt125 R 2004 I've just had the engine rebuilt, re-bore with new crank and piston etc. I've just had my bike out for a run about after about a month without being started. It started on the fourth attempt with the choke on and I let it sit for about ten minutes to warm up before I went out on it. About five minutes in to my ride the engine ran out of power and cut out. I pulled in the clutch and pulled in at the side of the road. Tried for about five minutes to start it and it eventually started. It kept doing this all the way home, stopped and started about four times till I got it home. It starts fine with the choke and will sit and tick over for as long as you like but it only runs for about a minute in gear and then cuts out. I've checked the engine oil, the two stroke and the fuel and they all appear fine. I'm pressuming the plug is fine as the bike ticks over. Any help you guys could give me would be very much appreciated.

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  • marlboro_ble Mar 22, 2011

    Hi DocPlayer, thanks for your speedy response.
    I'll try hooking up a new and clean fuel source in to the engine and try the bike in gear while it's on the bike lift so I can shift through the gears without having to go anywhere.
    If that doesnt help I'm not sure where to turn next. I know you mentioned looking at the carb but my bike is fuel injected. If it were a carb I'd be happy to try and fix it with the help of a manual but a fuel injection system is beyond my capability.



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Your description sounds like a fuel related issue. Try connecting an external fuel source and test again. there is a screen in the fuel tank that gets plugged, and so does the filter... If external source does not help, look into the carb(s).

Carry an extra spark plug, and when failure happens, pull the plug wire and hook it to the extra plug, and ground the plug against the engine.....does it spark? If it has a good spark, the ignition is not likely your issue. If spark is very poor, ignition heat issues may need to be addressed.

Posted on Mar 22, 2011


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