Was wondering how much the stock cyclinder can be bored before you have to replace the sleeve? Was wanting to do like a 424. Know people do the 416 with no problems but can the 424 be done without releeving? Also what cam do you guys recommend for someone who doesn't want to hardface the rockers and all? Is the HRC Copy any good? Looking for any help. Just got the 400 a few months ago and am racing mx just looking for a little more power. Have a FCR Carb on the way.

Thanks
David Chapman
2000 400ex
PEP ZPS shocks, eyeball swing, JD arms, LSR axle, LSR stem, Douglas billet beadlocks,

 

The stock cylinder can be bored to a 426 without sleeving. FYI, the stock 397cc bore is 85mm, 406cc is 86mm, 416cc is 87mm, and 426cc is 88mm. The 440 kits are an 89mm bore, and at this point you must go with a sleeve for this size piston. In my opinion the sleeve is too thin after boring to a 426, but some run this setup without any problems. I just recently bored mine to a 416, and went this route since I wanted solid reliability without overheating problems. Just my opinion...

I just learning about cams and the need for hardfaced rockers, but from what I understand, cams that are hardfaced during manufacturing require hardfaced rocker arms. Since the XR400 cam, HRC copy cam, and GT Thunder aren't hardfaced, they're designed to be run with the stock rockers. FYI...with my 416 bore I added an XR400 cam with stock rockers, and haven't had any problems so far. I also know of many others that are running the same setup as mine with the XR400 cam, and all used the stock rockers with no problems at all. I guess the bottom line depends on the cam you select, and whether or not you feel hardfaced rockers are worth the investment. If going with an aggressive hardfaced aftermarket cam such as one from Web or Poweroll you should definitely consider it, but for other milder cams the stock rockers should be okay. If nothing else, with a cam designed to be run with stock rockers you could replace the ones you have with new stock units. Hopefully someone more knowledgeable or with more experience can comment on this...

BTW, never heard of an Eyeball swingarm...is Eyeball the name of the manufacturer?

 

NVR2L8 Eyeball is a new company here in Vegas that is making really beefy swingarms and has just finished a jig on A-arms. They run a small ad in the back of dirtwheels and atv action. They kinda look like houser, but use a little thicker wall chromoly. As far as your 416 with the xr400 cam how do you like it? Did you have the head ported? I had a banshee before so the whole 4 stroke thing is new to me. Any other help would be appreciated.

Thanks
David Chapman

 

Hey fellas. I just bored mine out to a 426, I did the porting and polishing on my own, and I've got the White Bros. Pro-Meg exhaust system. I had to go with a 10-1 compretion ratio piston because the 11-1 piston was on back order until possibly Aug. Now, how do I like it? I love it! I am very pleased with the performance and I am also happy with the 10-1 piston because I can still run pump gas. The larger piston does cause a bit of vibration but it is really just barely enough to notice. To give you an idea on the power- It will run side by side with a stock raptor until 5th gear and then the raptor will edge slowly away. I'm confident that with a 16 tooth front sprocket I could take one through the entire range. It is very torquey, wich I love and I cant't wait to see what a good cam and carb will do for this engine. I hope this helps.

HP Racing[img]i/expressions/face-icon-small-happy.gif[/img]

 

I love what the 416 kit, XR400 cam, and FCR carb did for my motor. After this mod I can tell it pulls a lot harder than stock, and power is up everywhere. This setup still has quite a bit of grunt in the bottom end, but the XR400 cam does move the power towards the middle to top. The cam isn't a top-end screamer though, as you can feel the power drop as it gets close to redline. Just about any aftermarket cam will shift the power though, just depends on how aggressive of a cam you want to run. If you're looking for a decent increase the XR400 cam is one to consider, but go with something else if you're looking for top-end power.

No, I didn't have my head ported when I had the work done. The mechanic who did the upgrade cleaned up the exhaust ports a little, but left everything else alone as the rest of the head looked okay. He only charged me about a half hour of time for the head work--sending it off for more serious porting might be in the future if I go with a different // more aggressive cam. As far as porting is concerned I've heard mixed reviews about that...consensus says not to bother unless you're running a full race engine designed for top-end power...a simple clean-up job doesn't hurt though.