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CR250 keeps revving

#1 User is offline   Philip Galardi 

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Posted 17 April 2012 - 09:42 PM

I've got an 02 CR250, and while it runs okay I do have a couple issues.

Couple things first:
Top end has strong compression
reeds not cracked
silencer packing good
Using a PWK carb from a 2000 CR250

Problem/Symptoms:
1. Bike smokes out the silencer
2. Lots of black splooge
3. Takes 6 or 7 kicks to start when cold
4. This is the worst: If I'm running it in high RPMs, the bike revs high after I stop. Put me into a tree at Sandy Lane after the open section after one of the start controls. I was running wide open in the open section, then when I hit the woods the bike kept revving and I hit a tree with my shoulder pretty hard.

Any thoughts as to what my problem could be from? And yes, part of the problem is the connection between the seat and the bars. I'm a pretty lousy mechanic as can be seen by my very frequent DNFs.
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#2 User is offline   Glenn Plokhoy 

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Posted 17 April 2012 - 10:11 PM

Its lean, either from an air leak, clogged pilot ckt, or just too lean jetting. That old a bike I wouldn't be surprised if its a crank seal. Clean/check the carb, manifold for cracks, and post your jetting.

I don't consider sponge a variable to judge jetting as there are too many other considerations like oil, fuel, rider style.
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#3 User is offline   BILL ROTH 

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Posted 17 April 2012 - 10:28 PM

suspect your primary drive (right) side crank seal
bike use trans oil?
replace them both
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#4 User is offline   John Castaldi 

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Posted 17 April 2012 - 10:41 PM

definitely the crank seals. Do a pressure/leakdown test.

Either use a leakdown tester (with the proper tools) or the poormans method......

remove the pipe and the carb, plug the openings with expanding freeze plugs.
Take an old spark plug and drill out the center and braze on a tire valve.
Get a bike pump with guage and start pumping.
take the trans vent hose and put it in water/liquid
look for bubbles.
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#5 User is offline   Troy McNomee 

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Posted 18 April 2012 - 06:45 AM

I have an 03cr250 that had the same exact problem. I replaced both crank seals and checked for end play from the crank.
This did not fix my "running on" condition. I do recommend checking & replacing the seals as they are cheap insurance.
Double check the reed valves. I found the stock reeds will hit the inside of the intake tract while opening and chip the corners.
I replaced the entire reed block with a new stock one and the same thing happened again a couple races later.
The fix I found was to replace it with a moto v-force reed block, or a simaliar aftermarket one.
I agree it is a lean condition that is causing this and makes for a scary ride.

There was a post from Lisa about the current "Ethanol" in the fuel causing the seals to harden. I use VP C12 mixed 50/50 with quality super unleaded. Good luck
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#6 User is offline   Adam J Chadick 

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Posted 18 April 2012 - 08:45 AM

Dont forget the basics...... check the throttle slide, carb bore where the throttle slide slides in, disconnect the throttle cable from the carb slide and throttle and inspect it. if you dont disconnect it you wont be able to see the whole cable. it only takes one little frayed wire to make that throttle stick for a split second when you done need it to, been there done that. make sure the routing of it is smooth, make it as long and sweeping as possible tight bends make it bind and stiffer. also check the needle, roll it on a piece of glass and see if it wobbles, it might be tough cause its tapered, if its got a slight bend that could slow the slide down and make it feel like its sticking. all of the above are good checks too but dont forget the basics!
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#7 User is offline   CARL REHATCHEK 

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Posted 18 April 2012 - 06:12 PM

Also look at the boot on top of the carb where the cable inters as it could be drawing air/water and dirt in from there also.

Is that the first year cable operated exhaust power valve.. if you are dealing with a big smoker and gooing everthing up that may need a look also..

and a really off the wall item is the throttle cable routing correct.. as I owned a 01 and if it was not routed correctly it would pull at times and hang up.. produced some better scores..but also produced some brown shorts too..
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#8 User is offline   Glenn Plokhoy 

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Posted 19 April 2012 - 09:29 AM

Also, sand or dirt in the float bowl can be drawn up and jam the needle in the nozzle. Scary and expensive on a KTM300, ask me how I know. Route the carb vents from the vertical fittings up high so the carb will not pull a vacuum in the bowl and draw dirty water during crossings.
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#9 User is offline   wallace tunison 

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Posted 19 April 2012 - 03:52 PM

View PostAdam J Chadick, on 18 April 2012 - 08:45 AM, said:

Dont forget the basics...... check the throttle slide, carb bore where the throttle slide slides in, disconnect the throttle cable from the carb slide and throttle and inspect it. if you dont disconnect it you wont be able to see the whole cable. it only takes one little frayed wire to make that throttle stick for a split second when you done need it to, been there done that. make sure the routing of it is smooth, make it as long and sweeping as possible tight bends make it bind and stiffer. also check the needle, roll it on a piece of glass and see if it wobbles, it might be tough cause its tapered, if its got a slight bend that could slow the slide down and make it feel like its sticking. all of the above are good checks too but dont forget the basics!

Adam's right. The Basics. Check the slide to see if any of the chrome has worn off of the slide. If so,the bike will pull a lean condition with the symptoms being a leaky crank seal. Check the bore specs. of the carb in the slide area too.
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