88mm Piston

[400MXer]

i was wondering what this size piston takes your CC's up to. i know that an 87mm is a 416. but i was curious to what a 88mm is.

[Wheelie]

88mm piston will give a displacement of 425cc's

[Dave400ex]

Yeah a 88mm Piston is a 425EX. That will be a very thin Stock Sleeve. I was going to do the 425 at first, but I think I will do the 416 now. I`m not sure yet. It will be a while before I do the Motor on mine.

[400MXer]

so, would a 416 be more reliable?

[NJ300ex]

yes and no. If you get a bore done by some retard no work will be reliable but if you have someone like tc racing do it it will be. I would feel safer with the 416. Also a 425 puts out more heat than the 416

[Dave400ex]

Go with the 416. Who are you have do your Motor Work? I would have TC Racing. He is awesome with Four Strokes. The Stock Sleeve will be very thin with the 425. I think I will go with the 416. I`m sure the 425 will have more heat. The stock 400 is hot enough already. Call TC Racing and tell Tom what you want and where you ride. You will explain everything to you. He is great help.

Here`s what I want to do to my Motor:

TC Racing 416 or 425 Piston Kit
TC Racing XC Cam
Hinson Clutch Basket
Heavy Duty Clutch Springs
Get new Stock Clutch Plates put In
Pingry Oversize Oil Tank

That`s about $1000.

That setup is for XC Racing. TC Racing has a 416 National Motor Kit for MX Racing. You should check that out. He also has a 440 Kit.

[Wheelie]

I think a 416 would be more reliable than a 425, IMHO a 440 would be more reliable than a 425. Taking a stock sleeve that far would make me nervous. Not only that, if the engine grenades a sleeve will be necessary, if not a cylinder depending on how bad it grenades.

[400MXer]

WarriorMan

I'm having PR racing Engines do my motor. He is one of my sponsors. They are out of Toledo, Oh. They do pretty good work......and, i get it cheap.

[Dave400ex]

400MXer, Ok. I just wanted to know. Never heard of them. Do they have their own Cams and stuff?

[400MXer]

I think they use Web cams that they tested. They do a lot of testing. Like, they tested like 30 cams to see what one ran the best with thier porting and engine work. Check out their website.
They sponsored Harold "the bumblebee" goodman when he was just entering racing and untill he went pro.

http://www.prracingengines.com/

[patrick delao]

When your thinking about boring your motor bigger facter in what your going to be doing with it and where you want your power at , I always here people say this and that about heat and I run a 440 real hard and heat has NEVER been a facter so never mind the heat issue but where you want the power. The other thing about the 416 vs 440 being able to rev faster the 416 piston is only 1.78 grams lighter then a 440 piston both wiseco and both 11-1. Hope this helps.

[MikeL250X]

Remeber that bore alone (or displacement) is not the only factor in more heat, compression ratio will have alot to do with it, but if CR is equal on both then sure the higher displacement will make more heat, but there are ways around that. So say ou wanted a 440 but wanted to run regualr 93 octane stay with a lower CR, but if you could get race gas then go all out :D

[400MXer]

so, if i run 94oct. then would a 11:1compression piston be good, or should i use a 10:1.:confused:

Run a 10.8:1 piston,,it can run on pump gas and if ya want a little more power,,mix 93 octane with 110 octane. Overall the 10.8:1 piston gives a huge perforance gain,,while not making you use race gas.