First post here, hi I'm John.

My son rides a '96 Honda 300EX. It's a good quad for him and it still runs good. It is burning oil now though and is getting worse of course. Doesn't make any internal noises and still shifts fine, so I'm thinking I'll just do a top end rebuild to make it last a while until we can upgrade to a newer quad. We found a Wiseco kit with piston, pin, rings, clips and gaskets for about $100. I know a local guy who has his own motorcycle/atv shop who can bore the cylinder and diamond hone it. I'll hand lap the valves as long as they aren't too worn. I plan to clean out the carb while I'm at it.

I've rebuilt truck and car engines, but never a quad or bike engine, so I'm looking for some input on the details and any quirks about this model. Anything I should check while I'm in there? Not looking to hot rod it, just stop the smoking and make it last.[img]i/expressions/face-icon-small-smile.gif[/img]

 

Hello John, welcome to the forums. That sounds like it would work pretty good. Make sure you port and polish the head while your at it. But get some other guys oppinoins on here first. Im not great with the motor.

 

schonertkyle,

Thanks for the welcome. That's a good idea on the port and polish. I haven't done that since my mud racing days. [img]i/expressions/face-icon-small-happy.gif[/img]

Anyone have anything else?

 

Check the cam chain... make sure its in tolerance. Throwing one of these costs $$$$... also check the valve guides and make sure thats not how oil is getting burned. Check the cam and rockers also. If everything checks out it'll last another 9+ years. If you decide to port/polish realize you won't see much gain unless you have a decent pipe and have the airbox opened up with jetting to match.

 

i own a 86 trx 250 and in the oweners manual it says NOT to lap the valves? is there something different with my engine? it says it has a special compound in them that if a lap them i will distroy the seal. im planning on rebuilding the motor soon so im just wondering

 

Titanium coated valves are great, until the titanium is worn off, then the valves will go away fast. On the newer engine platforms running hotter exhaust temps, it is being advised not to lap valves as it may cause premature failure of the valve face and seat. I think the engineers are rethinking the use of titanium coated valves for this reason.

Welcome to the forum John

----- Gimpster -----

 

This sounds like what I had planned for my sons 300. I'll tell you what I found out. In ours, the rings were worn. (just like I would have geussed) While tearing it on down, the rod was loose on the crank, 2 of the valves were burned up pretty good. (Mickey Dunlap says this is VERY common) And the timing chain was wore out. I have put in a new rod, and a good friend of mine has a brand new 11:1 piston for a 250x that I'm going to use. (should put the 300 to about 12:1) It already has a White bro's cam and a Pro circut pipe, and been jetted. I've been waiting on the timing chain and hope its in today. Our spring break is next week and we would love to get to ride while the kids are off.
Good luck with it !!