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.
 
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.
 
Honda spent millions developing the CRF450 . I run a tuned stock carb , I have more power than I can use at most times .
 
I understand people are getting really good power staying on the stock carburetor. My engine is already set up for alky and it also saves me a good amount of weight because I don't have to run any cooling system for the engine. I have gotten a pretty good handle on adjusting the tilly at this point but do agree they can be a little bit of a head ache. I have the engine totally torn down and would like some input on any mods to build more power. Last year down at clay city when the track really bit up for the North South showdown I found myself wanting more power. That's not always the case but I figured if I have the engine all tore down I should consider other mods.
 
Never understood the need to delete the cooling system. The weight saving is minimal. Especially when you consider the need to carry 3-4 times more alcohol than gasoline. Gas provides a smoother power delivery and is easier to tune imo. I’d go back to the stock carb on good gas.
 
Is anyone running a stock carb on VP racing fuel?
Our kart was on the pole of that north south race. Sent you a message. You prob remember watching it run
 

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Our kart was on the pole of that north south race. Sent you a message. You prob remember watching it run
See, there you go. I raced with a gentleman who had every combination under the sun in his race trailer. His stock 450 on race gas was his best piece. Predictable, smooth and drivable.
 
I tried a tillson sold it back to stock carb race gas I haven't had the need for more power ever .just better tires and if I was just 30 years younger
At 60 this thing is is killing me but it a blast
 
I understand people are getting really good power staying on the stock carburetor. My engine is already set up for alky and it also saves me a good amount of weight because I don't have to run any cooling system for the engine. I have gotten a pretty good handle on adjusting the tilly at this point but do agree they can be a little bit of a head ache. I have the engine totally torn down and would like some input on any mods to build more power. Last year down at clay city when the track really bit up for the North South showdown I found myself wanting more power. That's not always the case but I figured if I have the engine all tore down I should consider other mods.
What’s trade off in weight carrying more alcohol fuel needed to cool the engine
 
Where are you guys getting your stock carburetors from? Are you buying used of eBay or finding a second hand supplier of a new carb?
 
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