I recently got a 03 kfx 400 and it was ran low on oil and wouldnt start by using the starter so i pulled started it and got it runnin but it would rev up and i had the throttle revved all the way up and it was like it was idling and ran for bout 30 seconds and started pouring smoke out of the pipe and as soon as it did i shut it down.Ive torn the engine down and got the top end off and the piston has some light scratches and the wall of the the jug also.I rolled the bottom end arounf and its moving good and the bottom end is tight.Could i have blown the rings even though the rings were all intact and the piston was intact.Im not sure where to start i just need help and making sure a seal is not blown in the bottom end plus the air box had a little engine oil in it after this had happened but no oil was in it before it cranked up.Any help would be greatly appreciated.

 

Obviously you will need a new cyl and rings that got scratched due to running low on oil. You said the bottom end was tight meaning, no free-play (good) or too-tight to turn my by hand (bad)?
The oil in air box is due to worn out cylinder that's pressurizing the crankcase which sends oil into the airbox.
Either you need to rebuild the top end only or both top and bottom end which means a complete engine overhaul.

 

Thanks for the info but yeah the bottom end was turnin really easy without a problem and i was planning on getting a new cylinder and stuff because it has a 440 kit in it.Im new to kawasaki and i got the bike on the cheap and i couldnt turn it down i was just wondering what i had gotten myself into

 

If it was run low on oil, I would take a look at the cam to make sure the lobes were not scored or damaged, and while its apart, replace the valve seals and maybe have the valves and seats lapped to make sure they seal up good.

 

Just to be on the safe side i would check the diaphrame slide to make sure the rubber is fine not cracked or torn or anything. i had a kodiac do the same thing it was low on power so i rebuilt it and low and behold the slide on the carb wen someone cleaned it got the diaphrame on halfway causing it to have no vacume to open wen you opened the throttle.

 

thanks guys for the imformation havent been able to be on here just had a baby so not had time to be on here

 

what do you mean by have the valves and seats lapped