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2004 CR250 help

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Picked this up last week. Didn't appear to have this "leaking" when I took it, but after an 8hr ride and 4 gallons of fuel run thru it I notice THIS:

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cr03.jpg

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When running it appears to "bubble" just behind the spark plug.

When compared to a friends 98 cr250 he said mine feels like it reaches +/- 5k rpms and kinda runs out of steam and "stutters"

I grew up riding an Yamaha MX80 that mixed oil itself..then went streetbikes for 10 years before I came back to dirt with a KX250. I owned it for 3 years back in 2000 then went back to street until last year when I picke up a couple of 4-strokes. SO I'm not NEW to smokes, but I don't have the familiarity with them I need apparently.

WTH is going on here?

With it "running out of steam at 5k" am I looking at a rebuild?

Just getting familiar with this bike and this section of the forum so please forgive the "newbieness"

If there are some good "required reading" posts here you'd care to share with me, I'd appreciate anything you'd like to help educate me with.

Thanks in advance

Edited by CasterTroy

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"bubbling" appears to be about 1/8 of an inch behind the plug, opposite the hose. Very small....almost like pin hole or something. It's odd.

"Stuttering" happens throughout the gearbox. If I had to describe it...it feels like a cold motor stutter in the top of the RPM range. Low end power is there, but lacks mid range, and no top end.

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sounds like it is running way too rich or pv issues. does it look like the goo is comming from the exhaust flange?

Well it's not STARTING at the exhaust...kinda ends UP there

Your spark plug is loose.

Checked that...not the case.

Like Ryan said...it "bubbles" from just behind the spark plug. No visible "crack" if you will. Just wondered if anyone experienced anything similar.

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Well it's not STARTING at the exhaust...kinda ends UP there

Checked that...not the case.

Like Ryan said...it "bubbles" from just behind the spark plug. No visible "crack" if you will. Just wondered if anyone experienced anything similar.

Is it possible the spark plug washer or sparkplug sealing surface has an imperfection? The other possibility is the head itself has a casting flaw (inclusion) that is the problem. If that's the case you might fix it with an aluminum epoxy like DevCon. But I'd probably just replace the head and sparkplug, not most cost involved.

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Stutter=rich, bog=lean. Lean out both needle and main jet. S7 Nozzle helps too.

That sounds like a plan!

Pulled the top off last night...cleaned, inspected. No cracks no nothing...but the spark plug washer/ring at the top was cracked...so that's likely the source of the bleed by

As I read about how crappy the carb is....sounds like I've either gotta make lemons out of lemonade or bit the bullert and buy that recommended carb :busted:

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If your on a budget find a 2000 cr250 carb on ebay, about 100 bucks, not quite as good as the air striker but for 150 bucks less im not gunna complain

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Also jd jet the mikuni for a lot less than a pwk, but the pwk has more rave reviews than the jd mikuni kit. My results have been very positive with the jd jetted mikuni, so much so that my airstriker sits on the shelf. Both good options.

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If your on a budget find a 2000 cr250 carb on ebay, about 100 bucks, not quite as good as the air striker but for 150 bucks less im not gunna complain

Ummm......

NEW FOR 2000:

All-new second-generation twin-spar aluminum frame and swingarm.

Redesigned engine ports, air intake tract and exhaust provide excellent high rpm output, improved low and mid-range power delivery, and more useable power throughout the rev band.

Slim new design with minimal bodywork. A redesigned seat creates a 10-15mm narrower profile in the seat and tank area.

ENGINE:

Larger airbox with 35-percent more volume is located 15mm farther forward.

38mm flat-slide Keihen (PWK Air Striker) carburetor incorporates a triple-taper needle.

Carburetor insulator features an internal step that smoothes airflow drawn into the engine.

Reshaped CRV rotary/flap exhaust valve has longer extensions at the side of the flap to better follow the exhaust port shape for increased internal turbulence, improved exhaust scavenging, and responsive acceleration.

Sub-exhaust valve port is raised 1mm to improve exhaust transition flow to exhaust valves.

Modified expansion chamber.

16-bit processor in the ignition CPU produces faster data calculation and more accurate ignition timing for the solid-state 3-D map-type digital ignition.

New dual radiators provide 10-percent more surface area and a 8-percent improvement in heat dispersion over the previous single radiator design.

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