Melted pistons= bad news

[slosh13]

Recently, after riding on a local MX track my stock 400ex motor blew having my wiseco piston melt to my cylinder. Apparently whoever did my motorwork only tightened two headbolts instead of all of them:eek2: So i am now in the market of buying new piston, rings, etc. What is a good combo for mx that a lot of people run? I have an idea for what i might want to do with mine and tell me what you think. Im open to any suggestions. Thanks.

JE or Ross 10.8 or 11.1 piston kit (w/rings and clips)
Port and polish
bore cylinder to a 416? would that lose reliability?
a new cam..what seems to be the best one for mx
new base,head,and valve cover gaskets
new spark plug

anything else im forgeting?

How much would this setup run for parts? I plan on doing my own labor also.

[ridered86]

get a 440 with a web cam port and polish carb and a descent exhaust. i seriously doubt that it was the head bolts, if it melted it was probably running lean.

[wilkin250r]

A 416 is going to be a little more reliable than a 440. And from what I've seen and heard, the 416 will rev out a little higher. I've heard of some 416's being almost as fast as a 440 (some even faster) because they will rev out better. The port and polish is definitely a good idea

[slosh13]

it wasnt running lean either. the mods i have on their now is a k&N air filter and a tc shorty pipe

[nakomis0]

Loose head bolts i wouldnt think would melt the piston.

And the guy who did your motor work tightened the bolts down. They need to be re torqued after a few hours or they will loosen.

.... let me guess the 2 bolts that where loose are on the exhaust side?

What type of fuel and what octane where u running? Any octane boost or other additives?

You sound like ur in the ball park on how to rebuild it. I like the 416 its a little cheaper and saves that money for some other mods.

[Colby@C&DRacing]

I feel the 416 kits when done right are the best HP for your money. I would use a JE or Ross piston with a hot cam stage II. Also I would recommend using a steel flex head gasket. If you are looking for more mid to top then I would also hae the head flow ported. This is a really good combo for MX:)

[Waynes400ex]

How good is a 416 440cc stroker if it doesnt have head work but a good drop in cam and a exhuast and 39 fcr oh yeah it has a air filter to. Is the stroker worth the money. It will be ridden in glamis and the mx track occasionally, will it wil reliable? what a good drop in cam ?

Originally posted by wilkin250r
A 416 is going to be a little more reliable than a 440. And from what I've seen and heard, the 416 will rev out a little higher. I've heard of some 416's being almost as fast as a 440 (some even faster) because they will rev out better. The port and polish is definitely a good idea

Bud I am not flaming you here at all but what you heard isnt really correct.

What happens is that way too many 440's dont get set up correctly and run crappy, trust me on this I even had the pleasure to had purchased one. It was a lot of work getting it right and a 416 with similar mods doesnt compare.

If you like look around some of the older threads and see what was causing these problems. Its really sort of interesting.

Now for the size debate you would find more $$$ left in your pocket with the 416 because all you need for machine work is the bore and that should run rom 40-90 depending on where you take it etc, and youdont have to the extra $75-125 on the sleeve the $100+ to get the sleeve installed and who knows what to get the case opening opened up.

BTW listen to Colby since he has his 416 running sweeeet. And deff get a carb with the porting.