06 YZ450F jetting for ice racing


7 replies to this topic
  • ditchound

Posted December 14, 2006 - 07:00 PM

#1

I am new to 4 strokes, been riding and racing a CR500 for the last 15 years. Did a search and could not find any suggestions on jetting for cold temperatures. Some guys in our ice racing club do not rejet their 4 strokes for winter!!! We usually ride in -20c to -10c and have on occasion ridden as cold as -40c. I would like to jet for -15c to be safe but the manual does not have a handy dandy chart like the one for the CR500. I could spend some time with a calculator and get close but with all the knowledgeable guys on this site was looking for a starting point. BTW I only have about 3 hours on the 06 so it is barley broken in, bought a yellow one in spring but was too busy to ride until this fall, but the 2 times I rode it the bike was awesome. The CR500 has more power but the YZ450 is faster, there is only so much traction in the dirt, that might change on the ice though. Oh ya, the 3 hours of riding time on the 450 was in cold temps (about 5c) but it seemed to start really easy and run really well even on the factory 42 pilot, very little popping on decel. 1600 ft elevation. After reading all the posts of way to lean jetting I was amazed it ran so well at only 5c temperature. So what do you experts suggest for a starting point?

  • 97chevy

Posted December 15, 2006 - 09:49 AM

#2

We run a 180-182 mj, and a 48pj in temps around 10 degrees F.

  • ditchound

Posted December 15, 2006 - 03:28 PM

#3

thanks for the info Chevy, as funny as it sounds I ran a 168 in the CR500 in the summer and a 180-182 for ice racing and it looks like the YZ450 will be the same. I know the jets are not the same but it is funny how the numbers are.

  • ditchound

Posted December 15, 2006 - 06:23 PM

#4

greyracer do you have any input on jetting for these temperatures?

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  • grayracer513

Posted December 15, 2006 - 10:06 PM

#5

I don't ever find myself in temperatures that low, and I wouldn't be tempted to go out and play in it, but using the correction formula I have, a 180 seems in the right range if a 165 works at 20c. My guess is that you would need at least a 48 pilot, maybe a 50, in order to make it respond well off idle. Some people have had trouble with winter starting and increased the starter jet to successfully fix it.

Four-strokes will tolerate being pretty lean, and even run quite well that way, especially compared to two-strokes. They will also put up with running way fat rich, too. But that doesn't mean they don't best when they are closer to being right.

  • Ulysses

Posted December 16, 2006 - 08:10 AM

#6

I don't ever find myself in temperatures that low, and I wouldn't be tempted to go out and play in it, but using the correction formula I have, a 180 seems in the right range if a 165 works at 20c.


Is that a secret formula, grayracer? If not maybe you can share it with us. I hope it doesn't involve differential calculus, 'cause my math is a bit rusty... :-)

  • grayracer513

Posted December 16, 2006 - 08:57 AM

#7

No secret. How are you with multiplication and division? :thumbsup:

I built the formula into an Excel sheet, so it's really convenient. Note that you can enter negative numbers for either temperature or altitude, which is handy when jetting for ice racing or if you live in Denver and want to know what to use for a trip to the SoCal desert, or whatever. You just put in the altitude as -5000 feet.

http://www.thumperta...700#post3029700

  • Ulysses

Posted December 16, 2006 - 10:22 AM

#8

No secret. How are you with multiplication and division? :devil:

I built the formula into an Excel sheet, so it's really convenient. Note that you can enter negative numbers for either temperature or altitude, which is handy when jetting for ice racing or if you live in Denver and want to know what to use for a trip to the SoCal desert, or whatever. You just put in the altitude as -5000 feet.

http://www.thumperta...700#post3029700


I can "multiply", but have no desire to do so and I'm ok with any division as long as they don't fire at me..... or, were you still talking about math??? :thumbsup:

Thanks for the formula.





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