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fastyz250

Buying a 2006 Yz450f what to look for

16 posts in this topic

HI i am about to trade my 2003 yz250 for a 2006 yz450f that has full exhaust and just had a new piston put in a yeaer ago and was wondering if there is anything that i should look out for or anything easy to check? any help would be great. Thanks

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Check the sticky's at the top of the Forum. Pay attention to proper chain tension and don't forget to check your valves once in awhile. A lot of guys are getting 200+ hours on this machine with minimal maint. I'm about to turn 100 hours with no issues.

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+1 on Chad's post.

My 2c: Check the valve clearance right away so that in 10 hours you will know if they're moving on you. Keep records of the valve clearances. Adjust them once. Do a valve job the second time they move.

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Is there anything he can look for when the engine is running to diagnose whether or not a valve job is in it's immediate future?

I was going to say hard starting, but that could also be carb related and not engine related at all.

Any kind of abnormal noises when the engine is running, or maybe more backfiring or something?

Just curious, good information to know if anyone can shed some light.

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The best thing to do is Run a Leak Down Test. It will tell you the overall condition of the engine and if you have any Valve leaks or Ring bypass, you'll find it then. These bikes reflect a lot of engine noise off of the skid plate so sounds can be deceiving. Hard starting can be an indication of poor jetting but also can indicate tight valve clearances. Backfiring can be jetting and most will argue that a little backfiring is normal and actually an indication of good jetting. If he has the time to leak-down test, that would probably be preferred. I own the Motion Pro Leak Down kit and find it easy to use and a great tool to track engine wear.

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Bring an air compressor to the seller and hook it up via a spark plug adapter?

Most air compressors have a gauge for the line and the tank, would that be sufficient enough to check for leaks at TDC on the compression stroke?

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no, your not trying to see how much pressure it will hold, your trying to measure the rate of which it is leaking...... I'm not aware of a way to to that without at least a better system than the standard compressor.

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I understood what you said.

You could use the line pressure gauge to tell if there is a leak, it will not drop in pressure until it is released, via a leak in the engine.

So you could hook it up, set engine at tdc on compression stroke, start the compressor and wait for the pressure to reach 50 psi lets say. Turn off the compressor and wait, the gauge for 100psi compressors will show even a loss of a couple psi..

no?

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yeah, but you're going to get pressure loss even on a new engine. Most tight racing engines will accept 5-10% loss. I think your system will tell you if your getting loss but I'm not sure If I would trust the accuracy of the system to tell me the rate of loss without comparing it to a leak-down gauge.

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Check the bearings. I bought my 06 used, less then 10 hours, so i knew the motor was good. But the bearings were already shot. All bearings exept the swingarm bearings were trashed.

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Thanks for all of the replies i will def look out for all of those things and hopefully this thing is nice

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Ask the seller the last time he replaced his fork oil. Both chambers?

I am willing to bet that the steering bearings are shot and the races are pitted.

The chain slider issue is a big deal, not something Ebay cannot fix. Two of my buddies that ride 06-09 YZs as well as myself have had the friction of the chain eat through our swing arms.

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i got the 450 today and it is a pretty nice bike needs a few little things and really needs tuned it bogs alot when you crack the throttle then it starts to move. all of the bearings looked great and the swingarm looks good as well. the bike backfires alot on decel but i kinda think that alot of it is due to the exhaust and it not having a clamp on the mid section allowing air to get in so i will hopefully get it dialed in soon and well see what happens. the bike has a full fmf exhaust with megabomb header and the quick adjust fuel screw and a few other little things.

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