450r Carb Jetting Help

[dustin_j]

Hi, I could use some assistance in jetting my 450r carb. I have the zrpilot adapter (which worked great), a UNI filter with pre-filter and no lid, the 40r carb, 406cc 11:1 JE piston, Hotcam stage 2 cam, and pro circuit slip-on.

Trial 1: I50 pilot, clip 4th from the top on the needle, and a 170 main. It ran alright, but would hesitate badly when I stabbed the throttle at low rpm.

Trial 2: clip down to the 5th spot from the top (thus, the needle is as far up as possible); everything else the same. This worked slightly better, but it would still hesitate.

Trial 3: 55 pilot, clip 3rd from top, and 170 main. The hesitation lessened, but still occurred once in awhile. I had to increase the idle to keep it idling.

Trial 4: same as trial 3, except the clip in 4th from top position. Throttle response seemed better, but would still stumble, though less often. Idle needed to be turned up some more, and would start to "race" after the engine was hot (idle would increase then decrease etc.).

I have a 52 pilot coming to try, but it runs well up until the rev limiter in 2 and 3 gear (I haven't opened it up more than that due to space). Does anyone have any ideas to get rid of the hesitation?

Thanks,
Dustin

[killer400ex]

did you try adjusting the fuel mixture screw

[dustin_j]

Nope, I'm assuming I should turn it counter clockwise to help richen the bottom end. Good idea, any others or should this fix it?

[zrpilot]

Read my sticky on jetting help, but I agree, you need to understand where the idle mixture is. BTW, you aren't stabbing the throttle while idling in neutral are you?

Adjusting the idle mixture screw should be done to get the highest idle, but if you have to go more then 3 turns out then go up to the next pilot jet.

IMO your jetting is not far off, I'll bet an adjustment to the idle mixture screw is all it will take.

[dustin_j]

All my trials were done under load; generally in 3rd gear. I will adjust the idle mixture screw tonight to see if that helps. It does seem close, but the occasional hesitation is irritating.

Thank you both for your assistance,
Dustin

[BassHunter0123]

mine did the same thing until i adjusted my screw.

[dustin_j]

It was the fuel screw. I started by counting the turns in, and it was alittle over 3. 1 turn out was decent, 2 turns out was alright, but 1.5 turns out was quite good. I might try 1.75, but it really works well as is. I'll have to ride with my brother's stock-carbed ex to see how much of a difference the 450 carb made, but it feels like I have a little more torque and throttle response.

Thanks again for the help everyone.

Dustin

[zrpilot]

Originally posted by dustin_j
It was the fuel screw. I started by counting the turns in, and it was alittle over 3. 1 turn out was decent, 2 turns out was alright, but 1.5 turns out was quite good. I might try 1.75, but it really works well as is. I'll have to ride with my brother's stock-carbed ex to see how much of a difference the 450 carb made, but it feels like I have a little more torque and throttle response.

Thanks again for the help everyone.

Dustin

Another successful 450R carb installation!

Enjoy the added performance!

[dustin_j]

Originally posted by zrpilot
Another successful 450R carb installation!

Enjoy the added performance!

Will do!!

Thank you again for the adapter and for all the jetting assistance. Your initial guess was surprisingly close, well done. :D

Dustin

[dariusld]

Originally posted by dustin_j


Your initial guess



:) :) :) :) :D :D :D When you say "guess", it sounds like he doesn't know anything:D

[dustin_j]

Originally posted by dariusld
:) :) :) :) :D :D :D When you say "guess", it sounds like he doesn't know anything:D


My apologies, initial recommendation ;) haha