Maintenance & Technical > KX450F / KX250F

06' 450F Hard to Start

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Scott Marks:
Just bought an 06' 450F, because the guy was having trouble kick starting.  Push it and it takes right off, but won't kick start.  He has has the head rebuilt with new valves & checked nearly all the electrical.  He thinks there is a problem with the wiring harness.  I am taking a simpler road, starting with the carb and checking all the basics and mainly cleaning to ensure there is no trash in the carb.  I took the Pro Circuit T-4 pipe off (which is for SALE at a resonable price) and put the stock pipe back on. Starting with all stock jetting, settings, and installing all new hot start components. Just wondered if anyone has any tricks or things to look for.

Thanks,
Scott

P.S. Make me an offer on the Pro-Circuit T-4 header & silencer

FPMXer:
If it's hard to kick start the valves could be out of tolerance. I know that my fo-fiddy is a pain in the butt to start when the valves are super tight. The right intake will be tighter than the left intake due to it getting the blast of intake charge. I can start my bike without the hotstart unless it washes out in a turn. Make sure the air filter is clean also these thumpers like clean filters and clean oil. I'd make you an offer on the pipe but I don't like pro-circus or it's parts. I'm also trying to sell my thumper to pay some bills off if you know any one interested. But while the carb is apart remove all the jets in the bowl, main area and there is a jet in the intake tube from the air box. Blow out all the passages in the carb. Check the spark plug for a light tan color, if it's black then the valves need to be checked and or shimmed.

Scott Marks:
Thanks for the feedback,  I put the carb back on and began kicking.  Nothing happened until I twisted the throttle a few times and then the big backfire.  Did this a couple more times so I decided to check the timing and valves. Exhaust are a nice .008 and I can't even get a .002 thru the intake. Should be a .005. 

FPMXer:
Do you have the factory service manual to do the valve work? If not I can send it to you in a PDF file. But the exhaust should be in the area of .17-.22 and the intakes at .10-.15 on TDC with the timing mark aligned with the notches and the cam lobes facing to the outside of the head away from each other.

Scott Marks:
Yes, I purchased a service manual.  I am at TDC with the cam lobes facing out. This is where I took the measurement I mentioned below.  FYI, when I took the buckets off the shim on the left side was marked 220 and the shim on the right side had a marking of 230. This would indicate the RT valve is tighter than the LT. Correct? Do you have any suggestions what shims I should get?

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