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Ryan426

no more pop'n!!!

19 posts in this topic

After adjusting 2 intake valves, sealing the header, replacing the plug with a CR8EK (CR9E which was rusted was in it when I bought it this past Jan.) & a little carb adjustment my '01 426 runs f'n great now. No more pop pop!!! Thanks for your input Gray.

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Sealing the header was probably key.

:thumbsup:Yeah I think so too. I took her out yesterday for the first time since I did all that and man, it idols now! Runs way better then when I bought it.

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After adjusting 2 intake valves, sealing the header, replacing the plug with a CR8EK (CR9E which was rusted was in it when I bought it this past Jan.) & a little carb adjustment my '01 426 runs f'n great now. No more pop pop!!! Thanks for your input Gray.

what made you change the plug other than the rust? i also have an 01'426:thumbsup:

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what made you change the plug other than the rust? i also have an 01'426:thumbsup:

when I bought the bike it had a cr9e plug. manual calls for a cr8e. I went with a cr8ek which is a better plug. the lower the #, the hotter the plug.

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I have a 2004 Yamaha YZ450F that I race offroad with. The last two races it starts this shootin' ducks routine half way through my second or third lap (avg. 7 mile laps). If I let it sit a spell it seems to run normal again for another lap or two but then it repeats the cutting out and backfiring.

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I have a 2004 Yamaha YZ450F that I race offroad with. The last two races it starts this shootin' ducks routine half way through my second or third lap (avg. 7 mile laps). If I let it sit a spell it seems to run normal again for another lap or two but then it repeats the cutting out and backfiring.

not completely positive but this sounds like valves to me... hot engine, hot valves = larger valves/cam lobes which equals tighter tolerances. when cold it doesnt do it because your valve lash becomes slightly more (read - just enough) to keep it from hanging them open. Definately worth a check to see if your intake valves need some adjusting...

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Oddly, valve clearance goes the opposite way on a YZF. The aluminum of the head expands more than the valves do, which moves the cams farther up from the valve seats as it heats, increasing clearance. This is why when one or more valves gets to the point where they are held open cold, causing a hard start due to a lack of compression, the same engine can be push started, and will be "OK" once warmed up. It's also how one can end up with less than zero clearance.

It's always worthwhile to check clearances, but the more likely culprit here is a coil, either in the stator or the ignition coil itself, heating up and failing. Test the stator when it's hot, see what it tells you.

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your knowledge never ceases to amaze me gray... crazy lol

thanks for the input, sorry I was again wrong hahaha these yz's got me all mixed up it seems

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Sorry in advance if this is a novice question but,,, what does it mean when you said that you "sealed the header"?

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Sorry in advance if this is a novice question but,,, what does it mean when you said that you "sealed the header"?

I took off the header and reinstalled using high temp silacone. then you let it cure for 12-24 hours.

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are you silaconen the header to mid pipe?? or both header to head and mid pipe?

Sealed the header to the head. Would'nt hurt to do the mid pipe Imo.

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on my mid pipe it looks as if i got some type of foam gasket? does that sound right? im not the first owner so i dont know if previous owner did anything to it or not.

Should i leave it on there and use silacone with it?

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on my mid pipe it looks as if i got some type of foam gasket? does that sound right? im not the first owner so i dont know if previous owner did anything to it or not.

Should i leave it on there and use silacone with it?

Foam?? ***!!! I would order a new one for the mid pipe. better safe then sorry bud.

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