[sixpacksewell]

Six years ago I bought myself a new 2008 CRF450R and my two boys each a new 2008 CRF250X. I know from reading the forum here that the ethanol wreaks havoc on these carbs. Oddly enough though, my daughter's 2007 TRX250 4 wheeler and my CRF450R don't seem to be bothered much. After 6 years of riding and sitting, they start fairly easily. But those two '08 CRF250X's are extremely hard to start and when they do, they will only idle on choke. I'd like to tune them-up and get them back into tip-top shape. Can you recommend, if there is such a thing, a carb kit that will work for both sea-level riding here in Texas and trail riding up in Denver around 10,000' above sea-level? Also, what are guys using for fuel stabilizer to prevent these things from getting gummed-up? We always turn the gas-off at the tank and drain the carb bowls when not riding, but they still get gummed-up.

[Leardriver]

Sounds like the pilot jets are plugged.
They are about $6 each, and just replace them with a #42 rather than trying to clean them.

They can plug after sitting as little as 3 months.

You can change the main jet for altitude if you want. The majority or riding is done with the pilot and needle. The main is only for wide open throttle.
A 155 main for the 450 and a 145 for the 250 will work for roughly 8,000 altitude, and you will be close enough.

[sixpacksewell]

Excellent Info, I appreciate the help. Keep the shiny side up!

[Leardriver]

I decided years ago to never crash again.
Sometimes I lean really low when the bike is nowhere near me, though.

[sixpacksewell]

I know what you mean! I had a "Yard-sale from Hell" a few years ago. I came off a jump vertical and stayed with it to the backside of the next berm into the trees. That left me limping for months. I'm over 50 now and if i want to keep flying I've gotta turn to trail riding. Fair Skies