what size jet for cold weather???

[305exracer11]

what size jet should i run, its cold out and my quad is running like $hit. i have a 300ex

[AndrewRRR]

There aren't any universal jet sizes for cold weather. You need to find out what works on your quad. Do plug chops, if the plug is dark, lean it out, if its white, richen it up. You can usually get 5 packs of jets for $15-$20

what is it doing? Backfiring?

[nakomis0]

Maybe this will help. When it gets cold you bike runs leaner. So I suggest you take your main jet and replace it with 1 size lrger.

[Honda99_300ex]

just get the pack of a couple diffewrent sizes and try those out....

[Butters]

305exracer11 - where did you get your 305 kit at?? what did it cost?

[cals400ex]

i can't see this being a huge difference between months of the year unless the bike was jetted wrong in the first place. in the summer i run a 150 main jet and in the winter months i use a 152. when racing another 400ex with mine there is minor differences but not much with jetting from month to month. i do understand, because i want all the power i can get too!! i would check the plug and see what it looks like. a tan color is darn close to where you need to be.

[danney f]

A 305 kit is an .120 over bore. Whit bros. sells the piston which is by Airias for about $165. Going that large in a stock sleeve will make it very easy to over heat.

[Butters]

then what is a good kit thats not to big that would be good? i don't want a 330 or anything.

[danney f]

HondaEXtreme01:

Here are some options for you.
If you don't what to spend alot of money but feel a big differance than a high compression pistion would be a good choice. I would say about a 10-1 ratio, that way you shouldn't have to run high octane gas.
If you what something that will give you more power than that you could go with Powroll's 76mm piston (.080 over bore) that will make it a true 300(297cc) which is a 10-1 ratio piston but could go all the way to a 13-1 ratio. If you where to go with this size the problem would be if you ever had to have it bored than you could go to the 305 but than there's that problem of the sleeve being to thin and overheating.
You may want to do what I did. I had a thicker sleeve installed and started off with the 305 piston and ran that for about 2 years. Than I wanted something a little bigger so I had a 313 piston installed and I love it. I had a thicker sleeve installed so that I can have it bored out larger and not run the risk of overheating and if anything ever happened I could have it bored instead of resleeveing. The sleeve is 84mm from outside to outside, right now with the 313cc it is only bored to 78mm on the inside leaving me with 6mm of sleeve. I could even go with a 330 kit in the same sleeve and still have 4mm of sleeve left. But I don't race(would like to some day,no time) only trail ride and to give my kids rides. But if you don't want anything like that than my first option would be the best. High compression piston in stock bore or over bore will make a big differance. Sorry, didn't think I was going to type that much.

[hondaboy400ex]

i agree with cals400ex hes doing it right

[frozenh2o]

Lot's of people don't realize how much temperature changes your jetting. You need to change 1% for every 9 degrees F. So on a jet of say 150, running perfectly at 80F in the summer, needs to be a 156 at 44F in the winter. Big dif, so if you want to be safe you better dial your jetting when it's cold out, then it will get richer as the weather heats up, and you won't fry anything.

[305exracer11]

so i should run 1 size larger jet. i think i have a 140 or 142, i got it pre jetted when i bought the carb.