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Problems with a 2003 Honda Cr250

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Hello

I am having some issues with my 2003 cr250. I replaced the piston this winter with a Wiseco piston together with a used Boyesen rad valve. I bought the JD jetting kit and replaced everything as it says in the manual. I am using the red needle in the middle position.

The bike was running good. I rode in the new piston and it pulled quite good , but when I borrowed it to my friend who is one of Norway’s greatest riders, he said that it didn’t pull good at high revs. He noticed that after one round at the mx track.

He reved it up for me, and on top revs it wanted to die. After he rode it, it was not good. When I tried to rev it out on the track but it didn’t want to. Its was like riding a 2 stroke with the choke knob on. When the revs got up it was like “ring ding ding ring RING DING !!! BRAAAAaaaaaapp…”lol, Cutting on the highest revs. My main jet was a 400. When I got home I looked at the plug and it was oily and wet. Rich.

Today I installed a 390 main jet just to see if it wanted to go. It was just the same.

When I rev It up it makes a weird sound in the air filter box. I have checked my filter and it seems fine. My air filter box is also fine, and there is no dust down in the air filter tube.

Something says there is a problem with my carburetor or reed valve.

I really do not know where to start looking.

I am also running a full FMF fatty exhaust system on it. I am also living near sea level in a colder climate if you wanted some more information to justify if my jetting is correct.

If someone do not understand what im talking about, I am able to make a little video of it when I rev it so you guys can see what I mean. Let me know.

Best regards

Jan and Norway

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Hello

I am having some issues with my 2003 cr250. I replaced the piston this winter with a Wiseco piston together with a used Boyesen rad valve. I bought the JD jetting kit and replaced everything as it says in the manual. I am using the red needle in the middle position.

The bike was running good. I rode in the new piston and it pulled quite good , but when I borrowed it to my friend who is one of Norway’s greatest riders, he said that it didn’t pull good at high revs. He noticed that after one round at the mx track.

He reved it up for me, and on top revs it wanted to die. After he rode it, it was not good. When I tried to rev it out on the track but it didn’t want to. Its was like riding a 2 stroke with the choke knob on. When the revs got up it was like “ring ding ding ring RING DING !!! BRAAAAaaaaaapp…”lol, Cutting on the highest revs. My main jet was a 400. When I got home I looked at the plug and it was oily and wet. Rich.

Today I installed a 390 main jet just to see if it wanted to go. It was just the same.

When I rev It up it makes a weird sound in the air filter box. I have checked my filter and it seems fine. My air filter box is also fine, and there is no dust down in the air filter tube.

Something says there is a problem with my carburetor or reed valve.

I really do not know where to start looking.

I am also running a full FMF fatty exhaust system on it. I am also living near sea level in a colder climate if you wanted some more information to justify if my jetting is correct.

If someone do not understand what im talking about, I am able to make a little video of it when I rev it so you guys can see what I mean. Let me know.

Best regards

Jan and Norway

Sounds like what my 94 cr125 was doing when the left side crank seal was bad. (flywheel side).

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You need to read the plug after a throttle chop run off the main jet. The oily black stuff could have come from the slow jet any idling back to the truck. Does your rad valve have a gasket on both sides of the valve? I would double check the intake side gasket for condition. It seals the entire cavity of the rad valve, but does not have any metal support except for the edges around the flange. It does sound like you are going lean up top not rich. Do another main jet run and do the chop, then inspect. Also inspect float level, and left side crank seal.

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You mentioned it was a used radvalve. What kind of condition are the reeds ? I would also check the slack on my powervalves. If the cables aren't tight enough the motor will feel like it doesn't want rev up top Also check & clean the carb for any debri.

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Hello!

I want to thank everyone for the great tips i`ve got! I love this forum!!:smirk:

I was hoping my crank seal was good so when i started to check out my Boyesen Rad valve i noticed this:

Untitlghged-1.jpg

:smirk:

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Wow, that would do it!! Did the retaining screws loosen up to cause that or is there something broken? Do you think maybe previous owner changed reeds and didnt secure and locktite fasteners or something?

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Wow, that would do it!! Did the retaining screws loosen up to cause that or is there something broken? Do you think maybe previous owner changed reeds and didnt secure and locktite fasteners or something?

Nothing broken, just the screws that almost fell out. And yes the previous owner did not use locktite on these screws, and thats quite important. You cant tighten these crews too hard or the reeds will loose its shape, or break.

I have used Locktite on the screws now and the bike started right up! :smirk:

But yeah, im so happy that the screws didn`t fall into the engine or something!

I was lucky :smirk:

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Heres my Cr250 we are talking about.

She loves to spin rocks and dirt on the 4 strokes, especially on the track :smirk:

Untitcr250led-1.jpg

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Sounds like the reeds may have come apart....

check that first.

You hit that right on the money, minibikedad, but why would it run rich, I would think lean (Too much air with no restriction). Is it because the air velocity is not adequate?

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Hi

Today i was out testing my Cr250, after i found out that my reed was loose.

I was first running with a 390 main jet but after looking at my spark plug after a full trottle run up a long hill, it was quite dry. The center electrode was a bit white, more like grey. The side electrode was also kinda greyish.Does this mean its lean ?

Just to be on the safe side i put in a 400 main jet. Bike ran good in tight woods (much low end riding) and on nice roads where i really could open her up.

I looked at my plug after a high rev/speed run and both the center and the side electrode was dry (grey in color)

After some slow speed woods riding, i got home and took some pictures of the plug. it does look like the bike is rich or will any plug be black and wet after slow speed runs ? would the center/outer electrode be wet and black if it was really rich ?

pictures:

plugg2.jpg

plugg1.jpg

I will take some pictures of the plug tomorrow after some high rev runs. Thats what i need to do to really see how the jetting is, right ?

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the higer rev runs with the chop will diagnose your main jet from 3/4 to fully open throttle settings. Below that your mostly on the needle, then on the slow jet+needle, down to slow jet, (and airscrew. ) Since you know the reeds were the big issue with the wot response, you should be ok with your previous jetting if it was in the ballpark. Plug insulator should read a nice tan color. Id clean that plug a little and inspect after riding next time. 400 main on the 03 is two sizes leaner than stock, Id be surprised if you really need the 390 in there, what the temp where you're riding? Whats your mix and ratio,needle clip, air screw setting, & pilot jet and float level?

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the higer rev runs with the chop will diagnose your main jet from 3/4 to fully open throttle settings. Below that your mostly on the needle, then on the slow jet+needle, down to slow jet, (and airscrew. ) Since you know the reeds were the big issue with the wot response, you should be ok with your previous jetting if it was in the ballpark. Plug insulator should read a nice tan color. Id clean that plug a little and inspect after riding next time. 400 main on the 03 is two sizes leaner than stock, Id be surprised if you really need the 390 in there, what the temp where you're riding? Whats your mix and ratio,needle clip, air screw setting, & pilot jet and float level?

Hi

Thanks for the help.

I was out riding yesterday and tried to get some pice pictures of my plug. When i took these pictures, i was running a 410 main jet.

Heres a picture of my plug after i tried to cleaned it.

1reinplugg.jpg

Heres a picture of my plug after a high speed / high rev run.

2pluggfullfres.jpg

3pluggfullfrez.jpg

Heres a picture of my plug after some normal riding on a mx track.

4pluggmxkjring.jpg

I was out right now and looked closely at the spark plug. With the 410 main jet the plug has a tan / light brown colour. Look at the last picture there, and check out the colour.

What do you think ?

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Hi

Thanks for the help.

I was out riding yesterday and tried to get some pice pictures of my plug. When i took these pictures, i was running a 410 main jet.

Heres a picture of my plug after i tried to cleaned it.

1reinplugg.jpg

Heres a picture of my plug after a high speed / high rev run.

2pluggfullfres.jpg

3pluggfullfrez.jpg

Heres a picture of my plug after some normal riding on a mx track.

4pluggmxkjring.jpg

I was out right now and looked closely at the spark plug. With the 410 main jet the plug has a tan / light brown colour. Look at the last picture there, and check out the colour.

What do you think ?

 

Isnt that last one a little lean? 

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