I recently picked up a 2000 400ex for pretty much a song and a dance. It has practically new plastics, nerf bars, white brothers seat and full exhaust, DG bumper, renthal bars, all in all pretty nice machine. The catch was it doesn't run and hasn't ran for probably 5-7 years. I am pretty good with a motor so figured I would take the challenge.

Got the thing home the other day and pulled the fuel tank to get out the ransid fuel, dissassembled the gummy carb and put it in a carb tank and started cleaning some stuff up. With all the plastics off I found out why it wouldn't run. No compression. Manual in hand, I pulled the head and saw nothing wrong until I touched the piston and it would rock forward and back. Big uh oh........ Pulled off the cylinder and found that the intake side of the piston was pretty much GONE!!! Probably going to take more than a quick hone to clean up the cylinder! LOL

So the question is, do I just bore the cylinder and throw in a new piston, or step up to the 440 kit with stage 2 hotcam? Typically around here a bore and piston will run about $240-250 then throw in a gasket set, looking at $300, I can do the big bore with stage 2 cam and gaskets for $400. So for the couple extra bucks is it worth it to do the 440? Are there things to be aware of? Does the 440 produce a lot more heat? Does it need extra cooling? Obviously it would need rejetted, any starting points for jets? Is it really worth it? I don't race nor will I race it, just like the power option lol.

Thanks for all your guys help!!!

 

Sooooo........song and a dance?, did he make you wear tap shoes and sing "My Sharona?"..lol.
You can have the jug miced out to see if it is badly out of round, that will determine what size you need to go for a piston/ rebore. A lot of guys have reported problems with the 440 kit as far as head gasket and heat problems. I bought a used 440 for my son years ago, and have not had one problem with it. That said, most would say the 416 or 426 big bore is much more reliable. Do that, open up the air box and exhaust, and you will see a nice hp increase. Hondas are solid and reliable, for 2 main reasons, they come with a low comp piston, usually 8.2:1, and a low reve limit on the cdi. Don't go nuts on the piston, a lot will say you need 12:1 for power, that will require premium or race gas / prem mix. A good overbore, 10.25:1 piston, cam, hardened rockers ( modded Hondas usually need this) will have that motor pumping out serious power over stock.

 

Rule of thumb on a bore job is go as little as possible. One step up at a time so you leave something for the next time. I would NOT go with the 440 off the bat. Two reasons. One is the rule of thumb above and the other is the 440 has problems.

 

If you have to sleeve it, its not a problem either. I had to have my 400EX jug sleeved in order to install the 500cc bbk. I do have the reverse oil flow mod. I have absolutely NO heat issues at all. Summer - winter my operating temp is 245*-250*. Never above that. I also have zero leaking / clamping issues as I was told I would have by members of various forums. Im running 500cc for almost 2 years now.

 

That's cool I didn't know you could go up to a 500CC. I been looking around and I think I am going to just go with a bore for now, and throw in a cam, and go up a couple numbers on the jets. What is the reverse oil flow mod? Haven't heard that one. I think I am going to put on a second cooler, I saw that on another post.

So I was tryin to get the motor out for the last couple days and the pivot bolt WILL NOT move, I can't even turn it, got the nut off, have been beating the bolt with a sledge, it won't give at all! Any suggestions? Some people have been saying that I will end up having to cut it, really don't want to do that....... for one because I have no idea how I will get the saw down there....

 

That pivot bolt can be a real beeeetch, your best bet is a good torch and some good rust dissolving penetrating oil like Kroil or Deep Creep. Patience is the key here, heat it up, soak it good, and let it sit for the oil to work, then heat it and beat it again, if its still stuck, soak again, repeat.

 

everyone else I have read online says I will end up cutting it. but if you think it will come out with time and stuff then ok, I will try it.

 

the reverse oil mod is available from 4 stroke tech ats about $150. its real easy to do it basically reverses the oil flow from bottom to top then oilcooler to were it goes from bottom to oil cooler then to top. keeps the cam an valves alot cooler. you dont get rid of your factory cooler. Google "Mickey Dunlap four stroke tech oil cooler"

 

I just looked in to it, it looks like a good idea. I was thinking of running a second cooler, but maybe that kit would be a better option. I am going to try and work on the bolt again tonight, I was really hoping to have it taken out by now so I can get it tored down and cleaned up. I really want to get it done and back together so the wife and I can go ride!!

 

I had a problem with big bore kits back in the day when I owned a blaster. I would just stick with your first option. I feel like everyone who uses a kit has problems in the near future.