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Crf450 lean impossible problem

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I have a 2006 crf450r this winter I did a full rebuild new hot rods crank Wisco piston and rings all new bearings and i put maybe an hour on the bike after rebuild ran amazing I rode it one day parked it and the next day it fired up first kick but within 2 minuets of running the pipe glowing red hot bike was running very lean back fire ring like crazy but idles fine I figured just a carb problem pulled it apart cleand it very good nothing wrong there put it back together same thing rechecked my timing and valve clearance everything is perfect took it to the honda dealer they couldn't figure it out please help noticed it is blowing quite a bit of air out of the crank case vent ontop of the cylinder head but dealer says that's normal any ideas

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You said you replaced the piston but not is you changed the compression ratio.

Anyways I have a 06 too and after hearing people talk over and over about replacing the carb slide seal and reading that your supposed to replace the slide plate and seal after 25 hours which nobody ever does because it's 50 bucks on partzilla I figured I'd replace it Atleast once. They say it helps with how crisp you carb runs down low. I put a high comp piston and stage two cam among many other things and my buddy with a crf450r 2011 would be neck and neck with mine. Being a 2nd gen with work mine SHOULD be a lot faster. ANYWAYS my bike was popping a lot on deceleration and I was thinking it was normal.. I soaked my carb In pinesol all day after tearing it apart this morning. Replaced the vacuum seal and plate, installed a ncvs needle(3rd position) r&d remote fuel screw 45 pilot and 180 main. I also have a r&d powerbowl 2 but I've been had that Got it all together earlier and noticed it sounded different when I cranked it up, def better. Man I took it out and only got to ride it for about ten minutes before the rain but I could def tell it's running a hell of a lot better and no popping... Point of all this is I've tried everything and that ncvs needle, vacuum seal and plate makes a huge difference. I ordered mine from partzilla

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I'll look into that today and ya it popping way more than normal not even rideable back fires on the throttle and off the throttle

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The air out of the valve cover is normal but a inch or so of oil in the gathering tube means your rings didn't seat or wernt installed correctly on your new piston.. The hot start is closed right? Also it should of received a new copper ring/gasket for where your header goes into the cylinder head. If this is missing or the header isn't lined up then air can get in and it will backfire a lot.. Just throwing ideas out there

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Yes checked all of those thing and still nothing iv checked for a intake leak in the carb boots checked the rings everything looks good even the dealership pulled it all apart and found nothing

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I just wanna ride missed the first race last week now this week is happening right now gunna tear the top end off again and check the head gaskets and rings see if I notice anything and I'll look at the carb seals to

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Pull out the pilot, clear the passage above it with stiff fishing line

 

Pull out the hot start and check the plunger for corrosion, and nut for cracking.

 

When re-installing the nut, be careful not to over tighten or it will strip, and put something on the threads to seal them

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I just checked the hot start everything is good and clean the but is not cracked or striped I put a little bit of Teflon tape around it so I'll see if that works and I have jet cleaners I just pushed thorough and I have a hindle pipe on it but it has not been jetted for it but it ran fine before so it shouldn't all of a sudden need to be changed right? It's just the silencer not the head pipe I'm going to repack the muffler today I don't think there is any left in it

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Fixed the problem finally can't believe it took me this long for somthing so simple it was just a couple of little shavings on the stator pick up causing the spark to delay making it have lean symptoms

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Cool deal man! Thanks for updating us incase we have a similar issue.. Koolaid! She's running the best she ever has mannnnn I really appreciate all your help!

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