High performance rebuild

[Drifterboy3]

Alright I have an 03 400 that a previous owner had rebuilt. In a fairly sketchy manner. It had gasket sealer everywhere and leaked oil from the the valve cover as well as the case. So I pulled the engine for a complete tear down. And am considering some upgrades while it's out. I would like to bore to a 440 and stroke. When I stroke I know I will need a stroker piston. Does anyone know if the make a 440stroker piston. Also for now I would like to get a stage 2 hot cam. Without new valves or springs will that work with the new bore and stroke or would I need a stage 3 hotcam. also I may bore this winter when I can't ride as much. So if I get a stage 2 cam with stock bore stroke and compression will that be ok?

I know this has been talked about before I'm just trying to get some clarification. Thanks for any help I get

[DragonGunner]

When you buy a stroker crank you can get the piston that is made for it then, usually sells in a kit. Wouldn't do stage 2 with stock compression.
Your valves an springs are good to go...if you rebuild have the head an cylinder checked to see if they need plained, could be warped an thats why they used alot of gasket sealer.

[Drifterboy3]

Where should I have it checked? I checked my self with a feeler gauge and straight edge. Everything was within limits. Also I just got the cylinder off and to my surprise found a namura piston. The numbers 8497 are printed on the top. Does that mean anything? I checked there website and couldnt find anything about those numbers. Then when I checked the application charts they only had standard and big bore (440) applications. Which would mean it has a high comp piston correct?

[#484]

The 8497 is the size of the factory bore I believe. 84.97 mm. I don't think namura makes a high compression piston, only stock compression. I've heard that they are nothing but trouble and melt fairly easily.

[AtvKid4Eva]

in my opinion you can make great power with a 400ex with just a high compression piston (11:1 426), stage 2 Hotcam, GT Thunder HD Head Studs, 02 CRF450r Timing chain and a 450r carb. It will be bullet proof and make awesome power. I think a stroker crank and a 440 is just too much for a 400ex. Id want to keep it as reliable as possible. Get rid of that Namura piston also. Go with Wiseco or JE.

[Drifterboy3]

Alright thanks for the info. I'm not as concerned with reliability as I'm not a beater and don't ride often. About once a month. Also I checked the ring end gap and my specs for first and second ring were opposite. Do you think A the first person could have flipped them by mistake or B could I get away with flipping them. Or what is even the difference to tell them apart

[Pittsburgh400ex]

I wouldnt bore it if its not needed. 407 or 416 all you need. 11:1 works great on 93 and any cam. Wont see anything with same build in a 426. If you want to spend the money and run race fuel can go 12.5:1.
Going straight to 426 just subtracts 2 future rebores. I only have it done cause i had to. I ride mine twice a week consistantly and hammer it fairly hard. No overheating or other issues. Correct jetting is the key!

[Drifterboy3]

Alright thanks for the info. I'm not as concerned with reliability as I'm not a beater and don't ride often. About once a month. Also I checked the ring end gap and my specs for first and second ring were opposite. Do you think A the first person could have flipped them by mistake or B could I get away with flipping them. Or what is even the difference to tell them apart

[xtreme762]

Originally posted by Drifterboy3
Alright thanks for the info. I'm not as concerned with reliability as I'm not a beater and don't ride often. About once a month. Also I checked the ring end gap and my specs for first and second ring were opposite. Do you think A the first person could have flipped them by mistake or B could I get away with flipping them. Or what is even the difference to tell them apart

The two rings are different. If you put number two in number one slot, and visa versa, they will probably work to make it run. But oil will not do what it is supposed to. Number two ring has a bevel on it, and number one doesn't. Not recommended to flip the two. They are not interchangeable.

You can get a manual somewhere around this site if you look for it.

[Drifterboy3]

Alright I'll have to check that and maybe buy new rings.

[Drifterboy3]

I checked the rings and it looks like I need another first ring. Second is good though well under specs. And the side clearance is well under spec for both also. That being said with another rebuild only a few months Away could I get away with This ring for now. It's at .58mm on te end gap and service limit is .50mm

[odog]

i love the stroker kit myself but it will get real expensive to get it built right

[Drifterboy3]

That's what I noticed about the stroker. Is yours bored also? Or how does the stroker compare to the 440