I did my first big bore kit install on a new KFX400. Installed the 440 kit. OMG!! Freakin fast. Tons of low end and power. Top end kicks *** too. The owner had to reinstall the stock sprocket cause the smaller one gave it wayy too much low end. You could putt around in 3rd gear and still get the front end to pop up. I put on the 440 kit, full HMF, K&N airfilter kit, precharger airbox lid, and rejetted the carb with a dyno jet kit. Its a bad *** atv to be reckoned with. I see why Team Green won a championship on it!

 

You may like it now but after you have replaced the 3rd head gasket you may have a different opinion of it lol. I used to have a KFX 400 that I bored out to a 440 it was great it was fast as hell and lot of fun to ride....not even a week after i had it installed the first gasket went in my DRIVE WAY of all places I was practicing holeshots......had a race 4 days later not too good...had to overnight a gasket to my mechanic and ended up costing $180 total for the whole deal...then about 3 weeks later while at a practice track it blew again....they fixed it this time for free....then about a month later it blew another one....they again fixed it for free.....Then I sold it! It was High Compression motor running on 110 Cam 2....also had Gibson LT a-arms up front and Custom Axis LT shocks all around it was a great bike until i put the 440 kit in it! Hope you have a better experience with yours.

 

Stock cams? Stock carb?
Cams and a carb also make a huge gain on the Z/KFX/DVX.

Good luck on the 440, let us know how it holds up.

 

Who did you get the B.B.kit from, Magic?

 

So far so good. The customer rides it a lot and believe me, he is hard on his toys. I met up with him at the river on the sandbar and he was ridin it like he was racin it, hahaha. I think the kit was from Yosh, not sure though. We were gonna use the stock base gasket so the compression wouldn't be too high. But we went ahead and used the gasket that came with the kit. He didn't mind adding octane boost to the gas. So far he loves it. We are all goin to Little Sahara over spring break. Glad we got it done in enough time. So far so good!

 

Cant ya O-ring the head/ gasket?