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Old 09-06-2014, 10:57 AM   #1
mr_bean OP
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CRF experts: help, my bike won't start

2007 CRF 250X:

I've had this thing since new. I have been meticulous with maintenance and have always used stabil in the gas. It's been bullet proof until now. Last time I rode (about a month ago) it was acting a little weird; it would occasionally misfire when I gave it gas at a low RPM. After that ride I drained the carb and put it away as I usually do. Since then the battery went completely flat (wouldn't respond to re-charging). I couldn't get it to fire it up even when I tried kickstarting. Now, I know the ignition system on this is very sensitive to low voltage so I just assumed the dead battery was the culprit.

New battery, cranks strong, still won't start. I have a strong white spark on the plug (re-gaped to spec) and the tailpipe smells of raw gas after a failed starting attempt. Occasionally it will backfire when cranking but other than that there's no evidence of combustion inside the cylinder.

Any ideas?

Thanks.
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Old 09-08-2014, 07:39 PM   #2
gatorgrizz27
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My bet is the pilot jet in the carb is plugged up, and stabil sucks for ethanol fuel. Every carb I've gone through with stabil and ethanol had hardened green deposits that had to be scraped out of it, worse than no fuel treatment.

Easy test is spraying starting fluid in the airbox, if it fires up it is generally a carb problem. I just fixed a customer's 250x last week that had the same problem, plugged pilot jet and stuck float. Went to a 42 pilot jet (100 degrees, 1000 elevation) and it fired up in half a second and ran great.

If it won't fire on starting fluid and you've verified spark, check the valves. The X models don't have the same issues as the R with beating valves to death but can still run out of clearance. If they have clearance you may have low compression and be in need of a piston and rings, bikes with this issue will usually push start and run well but not kick start.

gatorgrizz27 screwed with this post 09-08-2014 at 07:45 PM
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Old 09-08-2014, 08:20 PM   #3
wrk2surf
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like he said.. but when valves go out of spec its like a light switch it will run then it wont.. start on the pilot first...have you seen the recomended interval for a piston change on the X's ?
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Old 09-16-2014, 03:07 PM   #4
mr_bean OP
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Thanks for the reply guys.

Here's an update: I replaced the plug with OEM NGK (properly gapped) since the old one had a hairline crack in the insulator. Crank crank crank crank, no start. I was about to call it quits for the day and come back later to check valve clearance when I decided to give it one more go. This time I blipped the throttle when cranking (which I never do) and it fired right up and ran perfectly. The following day I went for a 20+ mile ride with no issues. After the ride it started acting funny again (wouldn't start) when I went to load it on the truck. I haven't touched it since.
First thing I'll check is the carb. Upon discussion with one of my riding buddies (who's owned many machines over many years) he agrees it's probably a clogged jet, specifically the idle circuit.

And yes, I've seen the replacement schedule for the piston and rings of every 15 hours, but that's "compeition use." I'm not hard on this bike at all.

Can you suggest what (if any) fuel treatment I should be using?

Thanks again,
The Bean
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Old 09-16-2014, 03:24 PM   #5
the_hulkamaniac
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I'd say valves first, esp Honda.

Get a set of stainless set in there, spend a little money on the top end.
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Old 09-20-2014, 07:50 AM   #6
mr_bean OP
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BUMP / update:

I checked valve clearances. One intake is 0.004" and the other is completely collapsed. I can't get my smallest feeler gauge (0.0015") in there.
Both exhaust valves are 0.010" (tight but still in spec).

Is this an indication that I need new intake valves or can I get by for awhile by just reshimming?

If I replace the valves with stainless will I need stiffer springs? If so how will this effect engine performance and cam lobe wear?

Thanks!
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Old 09-20-2014, 07:56 AM   #7
mcma111
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You need a valve job. You now have a bad valve and adjusting it will only last a short time until it closes up again. This is due to air filter maintenance. Ya gotta have a clean, well sealed filter or dirt will get past and kill the valves. Which is what you now have.

Kibblewhite stainless valves and spring kit and you will never have this issue again.
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Old 09-20-2014, 12:36 PM   #8
mr_bean OP
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Quote:
Originally Posted by mcma111 View Post
You need a valve job. You now have a bad valve and adjusting it will only last a short time until it closes up again. This is due to air filter maintenance. Ya gotta have a clean, well sealed filter or dirt will get past and kill the valves. Which is what you now have.

Kibblewhite stainless valves and spring kit and you will never have this issue again.
Thanks.
I was warned about keeping the filter clean when I bought the bike and I thought I had been doing a pretty good job with it. Guess not. I've been using nothing but Notoil on it every couple hundred miles.
Wrong filter oil? Not cleaned frequently enough? Or is the 1,200 miles or so I have on this bike about average for valve life?
FWIW, I pulled the carb off this morning and the intake track looks pretty clean.
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Old 09-20-2014, 01:06 PM   #9
mcma111
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Bel-Ray makes the REAL air filter oil. Nothing gets past it. That and Bel-Ray waterproof grease to seal the filter to the air box and this won't happen again.

http://www.belray.com/bel-ray-foam-filter-oil

http://www.belray.com/bel-ray-waterproof-grease
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BMW's
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79 R100s
91 R100gs

87 Harley FXRS-SP ~ 06 KTM 625 SMC ~ 72 Honda CB750/915cc ~ 92 XR600/654cc ~ 95 XR650l/675cc ~ 03 CRF450r ~ 05 CRF450x ~ 02 XR650l/675cc ~ 86 YZ490 ~ 93 YZ80 ~ 93 XR650l Project
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