yfm250 bear tracker bogs at WOT
#1
yfm250 bear tracker bogs at WOT
First, let me say thanks for all of the contributors here. I wouldn't have had the throught of diving into a new ATV project without a lot of help from these forums. Thanks.
I recently inherited a YFM250 BearTracker in reasonably good shape. Only thing I have found issue with is running a little lumpy at idle, which I resolved by cleaning and tuning the carb. It idles just fine now at about 1650 RPM according to the digital tach. I'm OK with that. The idle kicks up a bit when I pull the choke to first stop; goes wild if I have it all the way out.
I have an issue now with increasing the throttle; when I gas it it bogs down. It won't completely die, it will bog down to almost stall and then recover while it audibly isn't happy about it. I can feather it and keep it near 4000-4500 rpm, but can't get it any higher. It happens on and off of choke.
I have cleaned the carb twice and replaced the usual rebuild kit parts with the stock equivalents, checked the diaphragms, checked the vacuum operation of the slide. I eliminated the fuel filter and replaced the fuel line. I checked the bowl fuel level and it's between 1mm and 2mm above the mating surface.
I'm completely stumped by thing nearly dying at WOT throttle. There is a tiny 3-4 MM hole in the exhaust can, but no leaks near the the head, no vacuum or air leaks that I have found with smoke testing. The situation doesn't change with or without the air filter and/or foam.
Only thing I'm not good on is a new, fresh spark plug. I'm picking that up this afternoon.
I don't have the appropriate adapter for this heads threading to be able to measure compression, so I don't know if that is OK or not.
Does anyone have an idea that I might have overlooked or something to help get me through this?
-radio
I recently inherited a YFM250 BearTracker in reasonably good shape. Only thing I have found issue with is running a little lumpy at idle, which I resolved by cleaning and tuning the carb. It idles just fine now at about 1650 RPM according to the digital tach. I'm OK with that. The idle kicks up a bit when I pull the choke to first stop; goes wild if I have it all the way out.
I have an issue now with increasing the throttle; when I gas it it bogs down. It won't completely die, it will bog down to almost stall and then recover while it audibly isn't happy about it. I can feather it and keep it near 4000-4500 rpm, but can't get it any higher. It happens on and off of choke.
I have cleaned the carb twice and replaced the usual rebuild kit parts with the stock equivalents, checked the diaphragms, checked the vacuum operation of the slide. I eliminated the fuel filter and replaced the fuel line. I checked the bowl fuel level and it's between 1mm and 2mm above the mating surface.
I'm completely stumped by thing nearly dying at WOT throttle. There is a tiny 3-4 MM hole in the exhaust can, but no leaks near the the head, no vacuum or air leaks that I have found with smoke testing. The situation doesn't change with or without the air filter and/or foam.
Only thing I'm not good on is a new, fresh spark plug. I'm picking that up this afternoon.
I don't have the appropriate adapter for this heads threading to be able to measure compression, so I don't know if that is OK or not.
Does anyone have an idea that I might have overlooked or something to help get me through this?
-radio
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link to the video I mentioned.
The clip on the main needle is at the bottom of three stops right now, I moved it there from middle stop a couple hours of troubleshooting ago. I'm going to move it up and check each time for progress/change.
what a pain. this bike should run better than this.
The clip on the main needle is at the bottom of three stops right now, I moved it there from middle stop a couple hours of troubleshooting ago. I'm going to move it up and check each time for progress/change.
what a pain. this bike should run better than this.
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#9
First I wanted to say thanks to radio_spadio for taking the time post the solution to this problem. I have been wrestling with this same problem for a week and was completely stumped. I thought that I had read EVERYTHING about the Bear Tracker on the internet but somehow missed this.
The tags to this thread are a little lacking so I wanted to take the time to add a few that might help others.
1999, 2000, 2001, 2002, 2003 air fuel mixture screw needle pilot idle jet main floats intake manifold filter rich lean
Again, thanks radio_spadio
The tags to this thread are a little lacking so I wanted to take the time to add a few that might help others.
1999, 2000, 2001, 2002, 2003 air fuel mixture screw needle pilot idle jet main floats intake manifold filter rich lean
Again, thanks radio_spadio
#10
never would have thought it all needed to be buttoned up for the bog to go away!!