440 vs 426 kits

[jbrown9709]

Hi All,

I am planning on installing a big bore kit in my XR400. However, I'm having a heck of a time deciding between a 426 kit and a 440 kit. I've read every post about this that I could find. I've spoken with Rob Barnum, who recommends the 426, but I ride mostly nasty rocky rutted hilly stuff and my style leans toward lugging and tractoring up the hills. This would seem to lean toward a 440 to build a torque monster based on what I've read. Another thought is that I can add a hotcam stage 1 to a 426, but it isn't recommended for a 440 and a stage 2 leans more toward the high rev type riding. I plan on going with an 11:1 compression either way. Any thoughts?????

[XRIowa]

You can lug the 426 kit I ride all day and hardly ever touch the clutch. I can not compare it to the 440 never been on one nor do I have a cam. Do the 426 with 40% race gas and 60% high octane and you are set

[kiethco]

I have a Barnum 426, pumper carb and cam. I rode Coreys bike with the 440 for a weekend also. The 440 has a little more thump, but it did tend to run hotter than my 426. The IMS kit seems to be pretty popular, easy to do and trouble free. If it was me............I'd still do the 426, 11:1, add a nice 96 db pipe and the Edelbrock pumper carb.

I also compared my bike to my friend Nates bike. He had the same set up as me but no cam. One big thing the cam gives you is the tractor-ish hillclimbing confidence. ALot of times instead of grabbing a lower gear I can roll the throttle and it keeps making power. I hope this helps.

[CoreyClough]

If you would have topped the oil off it would have been full! Mine 440, STOCK CARB, Pro Circuit T4(louder than it should be, but I have a mod that quiets it down, a bit), and XR's Only Hot Start Kit with the decompression lever removed. Starts on the 4th kick, and never have had to rejet it since I bought it. Jetting? I have all the innard specs at home. Oops! gotta go back to work, here comes the boss! ?

[dale]

If you go with a Wiseco piston and 426 or less then you can get 10:1 instead of 11:1. The stock piston is only 9.3:1, so you still gain some. The 11:1 would be good if you go with a bigger cam, otherwise the 10:1 is going to run cooler and be more forgiving of both rider and gas type.

My 416 has had no negitives, I think I would go to 426 next time.

[Homey]

Do you think it would be a problem running only high octane pump gas with the 426? Do you need to juice it up with race gas, or does it matter?

[XRIowa]

I have ran my 426 11:1 compression on both race gas(40% mixed with HO octane) and pump gas it runs fine both ways. The race gas does give some giggle factor though.

[rsks]

If you go with 11:1 compression or lower, you can run super unleaded pump gas.

[YoungGunXR]

You cant screw up anything for running high octane gas can you? If not I may get some for races. How much are you paying for that mix xriowa?

[kiethco]

If you would have topped the oil off it would have been full!

Holy Moly, I put a new tire on, you want me to add oil also? Whats next...............wait, I dont wanna know! ?

[XRIowa]

It was like 3 or 4 bucks a gallon, Then I lost the gas can with my race fuel off my trailer ?

[2strokes_rule]

I had a 440'd XR and loved the power. It was dead reliable, and was an awesome hill climber. TONS of low end!

Coarse you couldn't pry my cold dead hands off these new fo'fiddies ?.