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Discussion Starter #1
My buddy has an 06 400ex we noticed tonight when we went out to the shed to start up the quads since it has been so cold these past few days. Well when he started his up and let it run for a min. at about 1/8th throttle we noticed his head pipes starting to glow right at the head. Could this be from it being so freaking cold out and it hasn't ran in a week? It runs great and always has. it's been jetted according to Dynojet's specs too. He can turn the choke about 1/4 the way on and the glowing will start to fade off. any thoughts for my fellow members? I figure it is due to the cold.
 

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In the cold the air is denser. He is running lean. That is why when you turn the choke on a bit it is getting the additional fuel needed to compensate for more air. Don't run it until you rejet for the cold.
 

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Discussion Starter #3
That makes sense if it idles though it won't glow at all if he get's up to operating temp you think he would still need to rejet?
 

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My brothers yfz450 pipe glows about 8 inches or so up the pipe at idle.

And thats normal.

Have you ran your 250 against his 400? I always wonder how mine would do against one.
 

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The only time you should EVER see the head pipe glow is if you are riding at night. If you see it during the day you ARE running lean. Yamaha sends there machines out rediculously lean. That is even lean for sea level. If you are anything above you are extremely lean. Tell your buddy to jet or prepare for an early rebuild.
 

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nah we've rejetted. It only does it at night. We've already rebuilt it once, because of the bad oil flow to the crank that the early yfz's had.
 

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Yep, I know all about their crap oil pump.
 

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Discussion Starter #8
He's jetted at 170 now with no box lid and yoshimura slippie. you can only see it glow if it's pitch black in the shop. I bet if he put the lid back on the fuel mix would be ok for cold winter riding. Like I said it runs great
 

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Yeah, put the lid on and he will be fine.
 

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Discussion Starter #10
Well the first 3 gears I can stay right with him but before I can wind out 3rd I'm eating his debris...lol What kin
d of speed have you been able to get out of you 250?



Have you ran your 250 against his 400? I always wonder how mine would do against one.
 

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The only thing I have raced on it was my blaster that I just traded for my 300ex. My blaster was pretty modded and fast, well fast for a blaster. lol the 250x would beat it by a bike length every time. I'm running 14/38 gears with 18" tires on it.

I really havent ridden it that much. I got the 250x a few weeks after I bought the blaster. I rode the blaster a ton last year and the x just sat.

I did race my younger brothers crf450 dirtbike and it blew the x away. haha His yfz 450 blows it away as well.

I'm getting ready to start riding the 250x seriously here once it warms up. I'm gonna learn how to ride competitevly(32's not too old to start right?) and figured It would be a good platform to start on then I'll eventually upgrade to a better machine.

Also once it warms up I'll put it against my mostly stock 300ex and see how it does. I'll try and get video of that.
 

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No 32 is not to old to start, i started back at 44 and racing every chance i get i run open c, +40 and 25+ money class against guys 1/2 my age and i can run with the best of them.
 

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My dad is 51 still doing 100+ mile desert races.
 

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Discussion Starter #15
My neighbor has a 300Ex with a pipe, jet kit and filter. I've raced him several times and beaten him everytime the 300 and 250 are the same except for stroke after about an 1/8 mile or more he just does start to creep up on me.

And 32 in not too old I'm 39 I don't race but I love to ride. Look at 69quadracer he's the bomb on a quad for an old guy...lol jk 69 you top notch in my book bro.


Also once it warms up I'll put it against my mostly stock 300ex and see how it does. I'll try and get video of that.
 
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