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2001 CR250R studders when you crack it, please help!

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New to the forum, but I read the posts all the time.  I could not find anything really conclusive on the issue I'm having.  I recently bought this 2001 cr250 for 1000 bucks, it ran ok when I bought it.  I re-built the top end right away because the guy gave me a top end kit, and it ran like CRAP.  It bogged down very bad when you cracked the throttle.  Low end and mid range sounded good, but not the top end, thick smoke and no power.  I checked all the basics and figured out a few things.  This dummy was running a 440 main jet with the air screw screwed in so tight that I had to beat on it with a hammer to get it unscrewed. (moron)  I could not even believe that the thing even started.  I cleaned the PV, exhaust valves, carb, float, reeds, plug, etc. gave her a little TLC and bam, she runs pretty good now.  Fires right up, wheelies thru all gears, screams, scares kids, etc.  But now I'm fine tuning her a little bit and could use some suggestions.  

 

The bike hick-ups for a half second or so when you crack the throttle in first gear.  I feel like it could be a little crispier.  

 

What are some things I could play with to try and fix this problem.  Pilot jet? (what size should I have)  Needle/float level?  Needle clip on throttle slide(carb)?

 

Anyone ever had this problem with a similar bike?  I'm kind of OCD when it comes to my toys running perfectly. :)

 

Any suggestions?

 

And just because I know someone will ask, yes I'm still running the stock mikuni carb :)

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New to the forum, but I read the posts all the time.  I could not find anything really conclusive on the issue I'm having.  I recently bought this 2001 cr250 for 1000 bucks, it ran ok when I bought it.  I re-built the top end right away because the guy gave me a top end kit, and it ran like CRAP.  It bogged down very bad when you cracked the throttle.  Low end and mid range sounded good, but not the top end, thick smoke and no power.  I checked all the basics and figured out a few things.  This dummy was running a 440 main jet with the air screw screwed in so tight that I had to beat on it with a hammer to get it unscrewed. (moron)  I could not even believe that the thing even started.  I cleaned the PV, exhaust valves, carb, float, reeds, plug, etc. gave her a little TLC and bam, she runs pretty good now.  Fires right up, wheelies thru all gears, screams, scares kids, etc.  But now I'm fine tuning her a little bit and could use some suggestions.  

 

The bike hick-ups for a half second or so when you crack the throttle in first gear.  I feel like it could be a little crispier.  

 

What are some things I could play with to try and fix this problem.  Pilot jet? (what size should I have)  Needle/float level?  Needle clip on throttle slide(carb)?

 

Anyone ever had this problem with a similar bike?  I'm kind of OCD when it comes to my toys running perfectly. :)

 

Any suggestions?

 

And just because I know someone will ask, yes I'm still running the stock mikuni carb :)

 

Find a jetting thread or chart for your bike. It will tell you EVERYTHING for all temp ranges and elevations.

 

Assuming everything else is mechanically sound and you are using the ratio recommended by Honda, you should be able to get it pretty damn close using a factory jetting chart.

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Bigpush.  I tried doing what the chart said and it did not run very good.  It suggested a 420 main, 35 pilot, AS- 1 3/4, needle 2nd clip.  I went down to a 400 main and it seems to better/best.  I have never messed with the pilot jet tho

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Are you sure the cylinder is installed correctly? I had a 94 and had misaligned #11 and #14 on this diagram. This caused a real lack of power because the PV wouldn't open. Yours may be stuck open which will kill bottom end. All I did was lift the cylinder enough to put the pin in the slot so to speak.

http://www.partzilla.com/parts/search/Honda/Motorcycle/2001/CR250R+A/EXHAUST+VALVE/parts.html

Also really go through your carb and make sure the choke isn't sticking and your slow jet is clear. 

Good luck.

Edited by SMarquez

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smarquez.  The crows foot is aligned properly and my PV is opening from L to H.  That is not it.  I'm starting to think my pilot jet is too lean?

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smarquez.  The crows foot is aligned properly and my PV is opening from L to H.  That is not it.  I'm starting to think my pilot jet is too lean?

What is your pilot jet? Have you adjusted the air screw as directed in your oem owner's manual? I am at 800ft and use a 32.5 pilot, #7 nozzle, one size leaner Honda needle(75) in the middle clip and a 410 main. If very cold I go to the 420 main.  The Honda oem manual chart is very good. The #7 nozzle really helped. Engine is stock otherwise.

Edited by YHGEORGE

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I'm honestly not sure what the pilot jet is currently.  I never looked when I had it apart. (not sure why)  I'm currently running a 400 main.

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I had one that did the same thing.  I posted what I did on here back in '09.  The float height was too high - I think I ended up at 17mm - and the pilot circuit was too rich.  Make sure you back the idle screw out so the slide can close all of the way when you are testing.  Set the idle after you have tuned the pilot circuit.

 

PeterJ

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Bigpush.  I tried doing what the chart said and it did not run very good.  It suggested a 420 main, 35 pilot, AS- 1 3/4, needle 2nd clip.  I went down to a 400 main and it seems to better/best.  I have never messed with the pilot jet tho

 

If your issues are on top, perhaps changing the pilot will not help. Pilot does low through to mid.

 

Using the correct needle? Crank seals could be sucking oil?

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Sounds like youre lean on the pilot circuit or needle.... or possibly have an air leak.

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What is your pilot jet? Have you adjusted the air screw as directed in your oem owner's manual? I am at 800ft and use a 32.5 pilot, #7 nozzle, one size leaner Honda needle(75) in the middle clip and a 410 main. If very cold I go to the 420 main.  The Honda oem manual chart is very good. The #7 nozzle really helped. Engine is stock otherwise.

 

 

you dont need to compensate and play the nozzle and the needle. thats why you do get to change teh nozzle to compensate for the  richer needle.

i use S4 with stock needle on 2nd clip. bike never bogs/blubber/load up and has power everywhere. i dont even rejet anymore.

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When you crack the throttle?

This would be partial pilot, but mostly needle. Try 1 step richer needle clip, do a lap, then try 1 step leaner.

How is the bike at 1/8th throttle? Any lean bogs?

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Sounds like a lower end air leak.    Check the crank seals on the lower end.   You can change them on a CR without splitting the cases.     Is there tranny oil going up through the intake manifold on deceleration?     Change both sides and go from there.     Don't waste your money on brass until you check this first.

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