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angelski628

2006 yz 450f only starts when hot start lever is pulled

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Alright everyone I need your help!!! I have a 06 yz 450f that ive had for about a year now and is in really clean condition and I maintenance the bike every week! Haven't had any problems with it until a month ago completely stumped on what it could be! The problem is its impossible to start and the only way is to turn the choke on and pull the hot start lever and it will fire up around 2-4 kicks. Once its on you have to immediately get on the gas or else it will die out. It even has this problem when your ridding and also has a lot of deceleration popping out of the exhaust pipe. All this is actually result of the engine jumping time a week before and after re timing the engine is when I came upon this problem. What ive done so far to try and fix this problem is re shimmed the valves they were slightly out of spec, replaced the spark plug 3 times incase I magically got 2 bad plugs out of the box, cleaned the valves and head and everything in there was all in spec, checked engine timing and valve clearance a hundred million times!, cleaned the carburetor 5 times and all the jets are clear and was all put back togeather to spec with stock jetting, bought and new hot start cable and choke, and ive also checked the simple things like making sure air filter isn't over oiled, engine oil is topped off, and I replaced the gas in case I had the curse of having bad gas! lol im at the point where I think my problem is ive been working on my bike with tools when I should be using a hammer and swinging it at every part! I am down to thinking that the stator is bad! does anyone have any ideas or heard of similar problems? anything will help!

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Have you cleaned the Carb......

I'm thinking pilot jet/ idle mixture screw circuit.

Good luck keep us posted.

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The pilot jet can "look" clear, but be obstructed enough that it doesn't work right.  If a .001" film of dried fuel develops in the metering orifice, it reduces the jet size by .002".  If you have a #45 pilot, that effectively makes the jet a #38.  Since a 42 is already too lean at up to 3000 feet or more, you can see why that would be a problem.  The fact that it pops excessively on decel and that it needs the choke on (the choke draws from the starter jet, not the pilot) leads me to the pilot jet.

 

Review this post regarding cleaning them:

 

http://www.thumpertalk.com/topic/681801-bike-wont-start-dont-know-what-to-do/#entry6879695

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Have you cleaned the Carb......

I'm thinking pilot jet/ idle mixture screw circuit.

Good luck keep us posted.

 

I'm thinking carb slide plate in upside down.

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I'm thinking carb slide plate in upside down.

 

There's another possibility, alright.

 

"Square" end goes down, not the rounded one.

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There's another possibility, alright.

 

"Square" end goes down, not the rounded one.

 

I may or may not have confused myself by installing that plate incorrectly once way back in 2000 when I was brand new to 4 strokes.

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Alright everyone I found out the answer to my problems! Last week I pulled the carb apart and took measurements on every part and found out the idle throttle stop screw was screwed all the way in and was seized into into position. Once I removed it I discovered the screw was only 1/2 the length it should be! I replaced it yesterday and adjusted it to spec and now now my bike starts up first kick no problems!!

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