Biggest main jet in a 450r carb?

[latheboy]

What is the biggest main jet anyone has tried in their 450r carb on a 400ex? I have a 426, full WB exaust, stage 2 cam , ported, and i am runing a 190 main. I have a 200 and a 205 order because it hasnt shown any rich symtoms yet. Just wonder how big of a main the carb will take before it just cant flow any faster?? lol

[pmptrk]

I have been wondering the same thing. I havent finished jetting it since the install, but showed no rich signs with 180 main. I have basically the same setup as you so would also love to see the answer to your question- sorry i dont have it.

What pilot are you running and how many turns on the a/f screw? Air box lid on/off?

[latheboy]

Im running a 50 pilot with the screw out 2 turns. When I jetted the main last week, i went bigger and bigger. All it did was make more power until I didnt have any bigger jets! lol. I will try the 200 when it comes in. It may be next week until i get it tho, I just ordered today.

[latheboy]

Oh yea, Uni filter with outerwears soft cover on airbox.

[latheboy]

Interestingly enough, Rico says he is running a 160 main?? Hopefully he chimes in.....

[pmptrk]

I noticed that too. I cant believe how much some setups vary. I though a 42 pilot would do it, and i am now at 3 turns out with the 48, so i will probably go to the 50 as you did.

Have you done anything with your needle?

Before reading this post i wouldn't have thought to go that high with the main, but i have a feeling im in the same boat as you- which is wierd knowing a 160's and 165s are working in some. Hopefully someone has an answer.

[latheboy]

I actually started witha 170 in mine. I went up, trying to get it to run too rich. It seemed to run fine on the 170, no lean popping or anything. It did make a ton more power on the bigger jet tho. My needle in in the 3rd groove from the top.

[Rico]

Well after seeing a jet chart comparing dynojets and keihn jets it explains things a little better.

I"m running a 160 dynojet which is equal to a stock keihn 177.

I still think I"m a little on the fat side and should drop it down a size which I"ll be going with a 155 and doing a test run before a race this weekend. If I hammer down and it doesn't pop or backfire then I'm going down another size until it finally does backfire on decel. Then I'll go up one size and call it quits. Funny thing is it ran decent with a 185 but ran better with each jetting change.

[2MuchChi450R]

don't forget to take altitude into consideration guys. What may be rich for some, may be lean for others :(

[underpowered]

my buddy is running:
13:1 89mm piston
+4 stroke crank (460cc)
MSD ignition
Stroker cam
GT thunder shorty pipe
Ported and polished head
+1mm intake valves

on his 450r carb, he is running a 45 pilot and a 220 or 230 MJ, runs great.

[pmptrk]

Did you try that 205? Any updates???

[latheboy]

I'll be out trying it tommorow. I will post results. I have been running the 195, and it still seems lean. I have a 200 and a 205 to try.

[babiak400ex]

$!00. you can get a Dial A Jet and save alot of the hassles of rejetting you start out with what you beleive to be a lean jett then you have 5 adjustments going one jet size richer with just one click each click. This is what I plan on using on when I install my 450 carb and I currently have this on my stock 400ex carb and works great. I dialed in my 400 carb in about 30min with this installed. Is suppose to be great for altitude changes to with out phyically rejetting.

[latheboy]

Good thinkin. Ive never tried them, prblably should. I am running the 200 main in now, runs right on!