Rebuilt 400ex to 406ex 11:1 stage 2 cam questions

[riley1374]

I just recently rebuilt my 400 to a 406ex 11:1 compression, stage 2 hotcam and valve guide seals all replaced. I was expecting a big improvement in the motor department, but it feels almost stock. Does the motor take some time to loosen up or could it be jetting? I am running 40 pilot, needle on 4th, and 155 main. Air lid on. It feels like it has more power up top, but feels bottled up. No popping or glowing headers, seems to be running fine, but no power like I expected.

[DragonGunner]

I have a 407 11:1 with a WEB cam which is close I believe with your Stage 2 Hotcam. You will loose a little on bottom an improve in the mid and top end. Having your lid on, is keeping things bottled up for you as well though. Adjust your jetting to like 170 main an take the lid off, your allowing the engine to breath an suck in more gas an air for more power. Also you will have enough power to go up a tooth on the front . I run a K&N with outerwear an a outerwear lid cover an a 180 main, choke removed,.....do you have a aftermarket exhaust?....that is a must of course.

[riley1374]

Thanks Dragon. It has an aftermarket aluminum airbox with the battery and electronics in it, so taking the airbox lid off is not an option. I think I may be lean. U think 160, 165 with lid on?

[riley1374]

Also, yes it does have a white bros slip on, stock header.

[Stickman400]

I don't think water is going to hurt the battery any if you take the lid off. I mean think of where it usually sits, right under the rear fender right where alot of mud and water gets thrown all over it, and it never has a problem. I'd say a 165 maybe a 170 if it'll run on it without poping on the top end.

[xtreme762]

This is exactly the setup I'm building right now. The difference is that I am putting a HMF comp. series slip-on, and custom built header on it. The custom built header will have larger tubing to help with the low end of power.

[DragonGunner]

Originally posted by riley1374
Also, yes it does have a white bros slip on, stock header.


Got the White Brothers E series slip on with stock headers....your good to go.....take the lid off an go up on jetting....make it an option.....you'll like it.

[CJM]

Without the right jetting and keeping the airbox lid on will make it feel worthless.

[riley1374]

Alright, you guys convinced me to take the lid off. Gonna bump up the jetting. You think i should get an aftermarket header also? Any thoughts on fmf or big gunn ones?

[CJM]

The headers on these bikes really cant be improved too much b/c of the way they are, dont waste your cash.

[Stickman400]

Yea, I'd listen to CJM. Jusr take a dremel and grind the excess splatter from the facotry welds off on the inside of the stock header where it goes into the head and call it a day. I have a Big Gun header and it isn't much bigger than the stock tubing, just bent alittle different.

[Zeb400EX]

I went from a stock header with the welds ground down and a hmf slipon, to a full hmf system and saw a pretty decent power increase. I run r carb to tho. so that might b the difference. Either way aftermarket (bigger) headers r worth the money. They will work better tho with other motor mods. Piston, cam, etc. Think about it. exhaust is heat. The more heat your taking out = more hp.

[Stickman400]

After I got done doing my full rebuild this spring I got rid of my Big Gun full exhaust and got an HMF full system and I didn't notice a whole lot other than sound. Maybe alittle bit better throttle response and bottom end power (prolly just in my head though), but that's it.

[riley1374]

Pulled the main jet yesterday.. Thought I was running a 155, turned out to be a 150. Popped in a 160 and turned into a rocket ship. Still waiting on a 165 and a 170 to see if i can go a little bigger, but liking the power improvement already.

[WoodTRD]

The 450r carb on my build (not too far off yours) made a huge difference...I ran the properly jetted stock carb for break in on my new piston and felt a pretty good increase over the stock piston, then threw the 450r carb on and it made just as big of a difference as going from the stock piston to 11:1 to me. Revs way faster and much better throttle response...so that's something fairly cheap to look into down the road also. Some have trouble with them but it worked out perfectly for me. Our stock raptor 700 can't hang anymore.

[Muzzgit]

Just as the three things that go together really well are slip on, jetting and a good air filter, the same goes for cam, hi-comp piston and ported head.

You are missing the ported head.

[riley1374]

On a budget, so the port and polish was not there. 450r for the right price might be comin soon. Just picked up some 450r front shocks to help out the front end.

Any thoughts on rear shock? Mine is pretty whooped. Aftermarket works or just buy a newer 400ex used?

[Stickman400]

Send the stock one off to a shock builder and have them so a full service on it with a re-valve and re-spring if needed for your weight and riding style. A forum member on here does shock service for a good price. Give him a shout at knightsuspension@gmail.com and he can get you set up.