Help on a 2002 CR 250 bogging

Big E
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Big E
Edited Date/Time 1/1/2014 11:47am
Just got a 2002 CR 250 and it's bogging after it runs for a bit when I crack the throttle open. It also does it off the face of jumps and landings. Could the jets be clogged?

If I shut it off it does not bog until on for a few min... Can any of you guys help me?
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Big Lenny
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Big Lenny 12/27/2013 10:23pm
12/27/2013 10:23pm
Big E wrote:
Just got a 2002 CR 250 and it's bogging after it runs for a bit when I crack the throttle open. It also does it off...
Just got a 2002 CR 250 and it's bogging after it runs for a bit when I crack the throttle open. It also does it off the face of jumps and landings. Could the jets be clogged?

If I shut it off it does not bog until on for a few min... Can any of you guys help me?
If it's a performance problem check the PV cables they HAVE to be tight or else it'll run like shit...
zombieland
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zombieland 12/27/2013 10:25pm
12/27/2013 10:25pm
run good gas , make sure the power valve cables are tight ,get v force reeds .
JW381
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JW381 12/27/2013 10:29pm
12/27/2013 10:29pm
Check the float. Not just the height but that it's sitting properly. Stock TMX carb I'm assuming?
PADDY'S LAD
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PADDY'S LAD 12/27/2013 10:33pm
12/27/2013 10:33pm
That's a lean condition. Check & make sure all carb vent lines are not plugged with dirt
My money would be on a little piece of dirt in the bowl drain plug. Under load that little dirt clod can be pulled up into the main jet thus, making your lean condition (drain &clean the carb)
Also check the air screw1 1/2 turns out & go from there.
Cheers, Pat

The Shop

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Harry_Gray
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Harry_Gray 12/27/2013 10:39pm
12/27/2013 10:39pm Edited Date/Time 12/27/2013 10:40pm
Swap in a CR 500 motor, put on a 10 paddle skat trak hauler on the back and chase chicks out @ Glamis until March. Sideways
Hut
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Hut 12/27/2013 10:41pm
12/27/2013 10:41pm
air leak? crank seal leaks are pretty common.
Floats need adjusted?
Chris O'Neal
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Chris O'Neal 12/27/2013 11:39pm
12/27/2013 11:39pm
I would head straight for the power valve cables! I've seen that so many times on those bikes and every time I've helped someone theirs' were way to loose.
Rizzo
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Rizzo 12/28/2013 12:06am
12/28/2013 12:06am
Big E wrote:
Just got a 2002 CR 250 and it's bogging after it runs for a bit when I crack the throttle open. It also does it off...
Just got a 2002 CR 250 and it's bogging after it runs for a bit when I crack the throttle open. It also does it off the face of jumps and landings. Could the jets be clogged?

If I shut it off it does not bog until on for a few min... Can any of you guys help me?
Without question, its the power bands. My friend put the blue power bands on his YZ 250 and after that, it was a rocket ship. There wasn't a bike or quad in sight that could hang with his bike at comp hill, those power bands were a big difference.
Driven71
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Driven71 12/28/2013 5:04am
12/28/2013 5:04am
Google "CR250 carb swap". You'll find tons of info on ditching the crappy stock Mikuni in favor of a Keihin PWK Air Striker. Did this on my '02 and loved it. Miss that bike...
CamP
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CamP 12/28/2013 6:04am
12/28/2013 6:04am
Make sure the pilot jet is clear and the float level is correct first. Also could be an ignition problem. A friend's bike was doing the same thing and it turned out to be a crack spark plug lead, which caused a misfire at the worst possible times.
hillbilly
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hillbilly 12/28/2013 6:27am
12/28/2013 6:27am
That is the pilot jet.

Remove the carb and take out pilot and main jets and also the atomization tube the main screws into.

It has rows of tiny holes that let air into fuel just before leaving the needle jet.

Once your are sure all that is clean put carb back on and adjust air screw at rear of carb to 1.5 turns out.

This is a good starting point. More turns out more air.

If the idle is turned in far enuff to make the bike sit there and run you dont want that.

A 2stroke should not idle more than 3 to 5 seconds.

The engine will hit much harder if the slide closes and fuel is pulled thru the pilot as you enter the turn with the throttle chopped

Then when twisting to exit turn the bottom case is loaded and ready to tranfer fuel charge into combustion chamber.

If you set the bike to idle forever it will cause the lean bog you described because it needs to be lean to idel like that.

Big mistake.

Also,get a gauge to check compression,if it is around 185 psi or less you can run low grade fuel in winter,cool temps.

Low grade fuel explodes the fastest giving you most power.

If it should ping the move up to mid grade.

If the psi is low you need a ring and piston,that can cause the bog also,weak compression.
Big E
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Big E 12/28/2013 6:56am
12/28/2013 6:56am
Man, this is all good stuff guys. I appreciate all the insight!

It does have the stock carb on it. I am going to take it off and clean everything make sure the hoses are not plugged and go from there.
Roscoe33
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Roscoe33 12/29/2013 3:51am
12/29/2013 3:51am
most pump gas today only lasts 30 days before it starts gumming stuff up, not enough perservative in it.
TeamPropainTurbo38t 12/29/2013 6:54am
12/29/2013 6:54am
Easiest check is to pull the carb and reed block. Check the reed edges. I had an 02 that bogged at "just the wrong time" several times. A bunch of near miisses. Ended up that the reeds were chipped. Dave
FGR01
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FGR01 12/29/2013 5:45pm
12/29/2013 5:45pm
hillbilly wrote:
That is the pilot jet. Remove the carb and take out pilot and main jets and also the atomization tube the main screws into. It has...
That is the pilot jet.

Remove the carb and take out pilot and main jets and also the atomization tube the main screws into.

It has rows of tiny holes that let air into fuel just before leaving the needle jet.

Once your are sure all that is clean put carb back on and adjust air screw at rear of carb to 1.5 turns out.

This is a good starting point. More turns out more air.

If the idle is turned in far enuff to make the bike sit there and run you dont want that.

A 2stroke should not idle more than 3 to 5 seconds.

The engine will hit much harder if the slide closes and fuel is pulled thru the pilot as you enter the turn with the throttle chopped

Then when twisting to exit turn the bottom case is loaded and ready to tranfer fuel charge into combustion chamber.

If you set the bike to idle forever it will cause the lean bog you described because it needs to be lean to idel like that.

Big mistake.

Also,get a gauge to check compression,if it is around 185 psi or less you can run low grade fuel in winter,cool temps.

Low grade fuel explodes the fastest giving you most power.

If it should ping the move up to mid grade.

If the psi is low you need a ring and piston,that can cause the bog also,weak compression.
Then why do they even have an idle adjustment screw on them to begin with?

I've never understood the logic of not wanting your bike to idle. My YZ250 will sit there and idle no problem and it hits like a ton of bricks when you wack the throttle exiting a turn.

By the logic of the slide closing and gas getting drawn in through the pilot, that means you are not pulling the clutch in for corners because you would need the engine braking to keep the engine turning over. However, most guys I know who run no idle pull their clutch in and keep blipping the throttle to keep the bike running. So they are not letting the slide close anyway.
vetmotoxer34
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vetmotoxer34 12/31/2013 7:42pm
12/31/2013 7:42pm
Well I used to have a 02 CR 250. I went straight to the source for expert advice. Tom Morgan Racing told me to use this below.

FMF Fatty Pipe
FMF Power Core II
V-Force 3 Reeds
93 octane pump gas
Jet for an avg temp of appox 70 - 90 deg F.

380 main jet, 32.5 pilot, 6BEY30-76 needle in the 2nd clip from the top, Wiseco #801M06640 piston kit only

My bike ran great after following those instructions.
Big Lenny
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Big Lenny 1/1/2014 12:50am
1/1/2014 12:50am
hillbilly wrote:
That is the pilot jet. Remove the carb and take out pilot and main jets and also the atomization tube the main screws into. It has...
That is the pilot jet.

Remove the carb and take out pilot and main jets and also the atomization tube the main screws into.

It has rows of tiny holes that let air into fuel just before leaving the needle jet.

Once your are sure all that is clean put carb back on and adjust air screw at rear of carb to 1.5 turns out.

This is a good starting point. More turns out more air.

If the idle is turned in far enuff to make the bike sit there and run you dont want that.

A 2stroke should not idle more than 3 to 5 seconds.

The engine will hit much harder if the slide closes and fuel is pulled thru the pilot as you enter the turn with the throttle chopped

Then when twisting to exit turn the bottom case is loaded and ready to tranfer fuel charge into combustion chamber.

If you set the bike to idle forever it will cause the lean bog you described because it needs to be lean to idel like that.

Big mistake.

Also,get a gauge to check compression,if it is around 185 psi or less you can run low grade fuel in winter,cool temps.

Low grade fuel explodes the fastest giving you most power.

If it should ping the move up to mid grade.

If the psi is low you need a ring and piston,that can cause the bog also,weak compression.
FGR01 wrote:
Then why do they even have an idle adjustment screw on them to begin with? I've never understood the logic of not wanting your bike to...
Then why do they even have an idle adjustment screw on them to begin with?

I've never understood the logic of not wanting your bike to idle. My YZ250 will sit there and idle no problem and it hits like a ton of bricks when you wack the throttle exiting a turn.

By the logic of the slide closing and gas getting drawn in through the pilot, that means you are not pulling the clutch in for corners because you would need the engine braking to keep the engine turning over. However, most guys I know who run no idle pull their clutch in and keep blipping the throttle to keep the bike running. So they are not letting the slide close anyway.
I don't have my bike set to idle because if I fall I want it to cut off...
CamP
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CamP 1/1/2014 7:12am
1/1/2014 7:12am
I set my 2-strokes up to not idle because Mitch told me so.

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FGR01
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FGR01 1/1/2014 10:11am
1/1/2014 10:11am
If I fall I want my bike to keep running so I can get going faster.

MXA probably says to run no idle also. I heard twin shocks are pretty awesome, too.
Bytor
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Bytor 1/1/2014 11:15am
1/1/2014 11:15am
I always had crisp as could be 2 strokes and they all idled. I'm with FGR, I want to be able to pick up my bike after a fall and get going ASAP.
CamP
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CamP 1/1/2014 11:47am
1/1/2014 11:47am
You guys need to quit falling so much.

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