Another 400ex with 450r carb jetting questions. SRY!

[latheboy]

I have a 426 11.5:1 Wiseco, stage 2 cam, open air box w/ uni, full WB header and an R4. Just put on a 450r carb. Started with 48 pilot, 170 main, needle in 3rd position from top, 2.5 turns out on screw. Quad started righ up. Revs up, but cuts out right away if the throttle is spiked. Switched out to a 178 main, and its much better, but still cuts out if throttle is spiked. Do I need to go bigger on the main yet, or do i need to adjust fuel screw?

Thanks

[latheboy]

Also, to add to the first post....

All i can do at this point is runs it a rev it a bit. I am in town and the neighbors dont like the sound of my R4 at WOT. Pansies. Anyway, I'm just trying to get the jetting close so I can just make one jet change when I get "out in the field."

[Rico]

Sounds like it's loading up with too much gas. Go down to a 165.

I"m running a 160 in my 416 and honestly think I could go down to a 155 and probably will next ride out to see what happens.

[latheboy]

I have been running a 155 in my stock carb. 34hp on the dyno. I tried the 155 in the 450 carb, but it still pukes out when i peg the throttle. All I can really do here is throttle it a bit, living in town sucks!

[Rico]

The choke isn't on is it??? Is the hot start hole plugged up???

[latheboy]

The choke is off. On the hotstart, is that the cable on the oposite side of the throttle cable? I just clipped the cable off and put a vac plug on it. Do i need to remove someting else from the hotstart? I noticed a spring or something in there.....

[Rico]

Originally posted by latheboy
The choke is off. On the hotstart, is that the cable on the oposite side of the throttle cable? I just clipped the cable off and put a vac plug on it. Do i need to remove someting else from the hotstart? I noticed a spring or something in there.....

Plugging it like you did is fine, don't remove anything.

I"m scratchin my head here.

[latheboy]

Im thinking Im lean on the pilot. I noticed some people have had to use bigger pilots. It doesnt rev far enought to hit the main yet anyways. Problem is, I dont have a bigger pilot. The pilot jet in the 450 carb is longer than the one that was in the stock carb. Seen that before?

[latheboy]

I put in a 50 pilot. 1.5 turns out on the screw. That seems to help, but the burp is still there. If I spike the throttle it will cut out and pop. If I let off before it dies, it will return to idle fine. It will rev ok as long as i dont bury the throttle quickly. Any ideas?

[latheboy]

I took a short video with sound. I can email it, if anyone can giver a listen. Send me a note kmbeck@tds.net

[perley03]

definatly lean on the pilot jet. when an engine just cuts out and backfires, its an indication that the motor is not getting enough fuel. when it bogges down when you have a load on it and it backfires only when you let off the throttle (sometimes) then it is loading up on fuel and the backfire is from the pipe exploding from the excess fuel in the pipe. i would go to your local honda dealer and get keihn pilot jets and mess around with them. i dont have a 450r carb yet so i cant help you out further.
go to http://www.motocross.com/motoprof/moto/mcycle/carb101/carb101.html
and check that out. it should help you figure out the problem depending on when it is cutting out.

[perley03]

you also said you run a 155 main on your old carb and put a 155 in the 450r carb...the whole point of putting a 450r carb on is to allow more air/fuel to enter the combustion chamber. the 155 would be too small.....think about it...your old carb is smaller so only a certain amount of air can enter it. if you go to a bigger bore on the carb more air can enter. if you allow more air but allow only the same amount of fuel in then it is lean. i would try a bigger main and a bigger pilot jet. start out at standard on the screw and if its still backfiring screw it out 1/4 turn incriments. if you go more than 2-1/2 then try the next size pilot and reset back to factory and screw out .....etc

[latheboy]

I put in a 170 main to start with. I thought It was strange that Rico (post above) runs a 160 main in his 416 setup. Whatever is working!

[perley03]

you said it is cutting out as soon as you nail the throttle....it is a pilot jet. your main jet hasnt even come into play yet. i would try changing the pilot first and get that squared away, then work on the main jet. the main is 3/4 throttle to wide open. try doing this on a load instead of just revving. let me know asap
also you might have to rejet when it warmes up just letting you know

[latheboy]

I cant run it under load until tommorow. I can get on the throttle, but not real quickly. What really stinks is I dont have any bigger pilots, and no one around here does. Dang!

[perley03]

if you need to go riding put back on your stock carb for now till you can get some pilots it will work fine for now

[latheboy]

Well, I went out to ride. I started out with a 50 pilot, fuel screw 2.5 turns out and a 170 main. Seemed to run fine, but once in a while I would get a little pop or bog if I nailed the throttle real hard. I decided to keep going up with the main until I got some rich running symptoms. I took it for short runs ( 2 min max after warm) between each of these jet changes: 170, 172, 178, 185, 190. Each jet bigger made the quad pull harder and harder. Never once did it burble or seem way rich. I settled on the 190 and ran the rest of the afternoon. The carb seems to be a great upgrade and I am happy with it! It pulls way harder in 3rd now. Seems like this is a way bigger main than most are using in a 426. Just to recap, it has a stage 2 cam, 11.5:1 wiseco, full WB header with R4 and a WB rev box, uni filter with outerwears soft cover. Thanks for the help guys.

[goinnukinfutz09]

I have a 440ex and im running a 450r carb on it. I have a 185 main jet and it runs prime. It may sound fat but it's perfect for it.:eek2:

[latheboy]

I got no problem dumping gas in it, it screams! I was kinda hoping I could get a rich burble out of it, then i was going to go back down one size. Im just guessing, but I doubt the carb will even flow much fatter than a 195 jet.