Ok so i have this beast of a 400ex i bought about a year ago, has run great since i got it. the guy i got it from told me i would have to adjust the valves every couple of hours so like the lazy bum i am, an never really had experience tweaking with the engine i never adjusted them. so it has a bad sounding tick in the top end. i was adjusting them last night and was trying all kinds of different tweaks cause the stock adjustment still had the ticking in the top end. i have a curtis sparks x6 ehaust on it and the guy i got it from has some jetting done to the carb but i haven't got to lookin into that yet. anyways i knew i have fukks something up probably from my laziness of turning a few bolts so i tear the top end apart and it hurt to see what i found. imma put the picture up but the rockers at the top of the motor which rubs on the hot cams lubes was all messed up the cams lube is teared up and the piston is bad. the main thing im asking is since it is already bored to the 426cc i dont want to go to the 440 because of the loss reliability whats the most economic way to go with this, i love the bike style and just great all around bike hate to get rid of it so i wanna really put some work into getting it right, any suggestion would really be appreciated as it is the first time tearing the top end off a 4 stroke. thanks a ton

 

if you bored it out withouta head squish or getting a different head that messed it up. if the piston is high compression and you ran normal pump gas, that messed it up. if it got a notch out of time when reassembled to 426 that could have messed it up. I might be getting a 400ex for my brother. I told him to just get aftermarket air filters and pipes an tips.

 

i bought the bike off cl and it had already had allready been bored out, i wanted a reliable bike and i love the hondas older fourwheelers run for ever stock as long as you change the oil so i have never have messed with motors so i kinda was opening the motor to have to find what someone else had already done to it. he sounded like he knew what he was doing and did he research.

 

always ran 93 , should i have ran race fuel if the piston is high compression

 

Nothing to do with you, the reason the previous owner had to re-set the valves all the time was the worn cam. All those broken bits of liner will need to come out of the bottom end and gearbox. A new cam, new cylinder, or liner (if available, and will stay in place) and new piston is a minimum. Or used parts. The head is badly coked up, but I can't make out from your photos, if it is serviceable.

 

Yuk!...what a mess...hopefully you can get the cylinder re-sleaved instead of a new one. If you buy a used cylinder, have it measured before buying a piston, or better yet just have it bored and a piston matched at that time. The trick is getting all the metal out...you will be splitting the cases...which is a task all in itself...


The valves are pretty carboned up...clean those real well and look for valve damage too...

 

OK thanks a ton i really appreciate the feed back imma take some better pictures today, yea i was planning on get the valve out and clean and make sure they were seated just couldn't find the tool to hold the springs down. And oh dear spliting the cases will be fun i figured id have to cause i know the all metal has to be in there somewhere half came out in the oil

 

Here are a few extra pictures