CRF450 help

Blakec9

Member
Hello guys, running a CRF450 on meth and had a question. Is it ok to close the low side on the tilly carb when you start it on the grid, then turn it up once you get on the track. I have noticed with my built motor I get a lot of blow by if I let the engine idle much with the carb set to 2.5 out on the low. My thought was to turn it to 1.5 out when starting and idling. Any suggestions or input is appreciated. Thanks!
 
Sure can. Tilly’s especially on alcohol aren’t meant to idle on green flag settings, ever. Lean her out for sitting on the grid and roll your needle back out when you get moving. Tillotsons WILL fill your crankcase up if you feed them too much fuel under idle. A lot of guys on here think they’re inferior carbs because they interpret the needles as one and done catch-all setting for any condition and subsequently have issues that they can never chase out because they can’t tune one. Get familiar with it, play with the needles while in the seat and you’ll be confident in your changes in no time.
 

Blakec9

Member
Thank you for your input. That is exactly what happened to me. Filled the crank case full because I let it idle a while. Another question I had was, Should I lean it out until I start to see my water temp rise or stuttering on accel then start turning her out until temp stabilizes or clears out on throttle. I was told to set the low side to 2.5 and high to 1.5. Do these settings seems correct?
 
Thank you for your input. That is exactly what happened to me. Filled the crank case full because I let it idle a while. Another question I had was, Should I lean it out until I start to see my water temp rise or stuttering on accel then start turning her out until temp stabilizes or clears out on throttle. I was told to set the low side to 2.5 and high to 1.5. Do these settings seems correct?
It determines who set the carb up for you. I had Dustin Stephenson do my HM1 for my 250 on gas and it was set up for 1.5 on both needle. He did a 191 on alky and it was also set at 1.5 on both. Other guys do them differently. As to leaning it out on the grid don’t get carried away,1/2 a turn should be plenty. Don’t start it up until you’re ready to go. I would run it at 2 tiurns for the start and going down the back straight I’d give it the 1/2 turn back. They do make a remote need adjusters where you could mount on your steering wheel so you don’t have to reach over. Hope this helps.
 
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