Stock Bore??

[EXDUNER127]

What kind of power gain will i get out of a stock bore with 11:1 piston and stg 2 hotcam on my 400. will it be worth it. how much diff. could it be compared to a 416??

[tinner]

There's a big difference over stock. But seeing that you already have it torn down...I'd spend the extra $35.00 and get it bored out. You'll be happier. Mine is a built up stock bore, and I think I'm going to tear it down this winter for the 416. I need more torque.

[Jay300ex]

EXDUNER:

Just thought that I would tell you that increasing your bore size inceases your horsepower whereas increasing your stroke will increase your torque. Cheers =)

[Antnee77]

Originally posted by Jay300ex
EXDUNER:

Just thought that I would tell you that increasing your bore size inceases your horsepower whereas increasing your stroke will increase your torque. Cheers =)

That's weird, I was just gonna say that. He's right, increasing the bore is not gonna increase the torque, you need to stroke it.

[cals400ex]

if you dont' want to bore it out, don't. most will say to bore it out. i have had a 406 and a 426 and the difference isn't huge. i did gain torque with the 426, but that could be from several things. i lowered my gearing 2 teeth on rear sprocket, i switched from a stage 2 hotcam to a more powerful all around TC mx grind cam, and i raised the bore 2mm's. also, i had my pipe thermal coated along with the piston when i installed my 426. also, the compression on the 426 was raised about a 1/2 a number. all in all, the difference isn't huge. my 426 doesn't rev as high as my 406. it does have more torque though. overall i am happier with my 426, but you need to take in consideration what all i had done or changed when i put this together. i actually sold my 10.6:1 406 ross piston to a member on this site. he put this piston in and a stage 2 hotcam. his only other engine mods are a stock jetted carb (which really isn't a mod, but something that needs to be done) and a powerbomb header with an FMF silencer. he went to the dyno and put out 37 horsepower with just these mods. :eek2:

most of the 10.8:1 416's that i have seen on the dyno only went 34-35 horsepower. i realize that each dyno is a bit different and the kind of tires you run will cause fluctuations too. but, this is still very very impressive in my mind.

if you want to spend the cash, go ahead and stroke it. if you don't, just do a regular higher compression piston. i find more of a difference with what cam you run. my buddy and i both had 406's. he now has a 416 and i have a 426. so, i have had time on these all. the stage 1 hotcam was a great cam for trails or for tight sections. it produced decent gains accross the board. the stage 2 hotcam wanted to stay in the upper rpms. at low rpms, it wasn't great. get them up and the bike will then move. the TC cam was another high revver. down really low it wasn't all that strong. in the midrange it hits hard and stays there all the way past the rev limit. i would consider the grind similar to the stage 2 with a harder hit before you get to peak rpms.

good luck with your decision. i don't think you will be disappointed whatever route you go.

[jedman]

Cals right about everybody telling you to bore it out. I was gonna just change the piston and everybody said to bore it out. I now have a 416 with the HRC cam and absolutely love it. It's a big difference. I can keep up with my buddies quads. They have a raptor and a 450r, both piped. Hope this helps you in deciding. GThunder did my motor work, Laz does great work.