piston?

[01boneless]

ok i know this has been beat up so much but i need some help lol i know wiseco and je are top brand pistons. but how is namara pro x anthea any good? also what would be the size of the piston on a 402? and how many over do i need to bore to get to a 402 thanks guys

[bkb88]

I'm guessing that it would be an 85.5mm piston. My bike is running a 86mm piston which brings my displacement to 406cc's. From all the research I have done on piston brands, Namura is the one to stay away from at all costs. Do yourself a favour and buy either a Wiseco or JE piston. Both are of very high quality and I'm sure everyone else will agree that your motor is not the place to go cheap on inferior quality parts. Just my $.02.

[05DodgeDakota]

Pro-X is Wiseco's economy brand IIRC

[matts27]

Good gasket set $60. Clutch case OEM gasket 35$. Spend the 100-120$ and get a good piston and ring set (JE/Weisco). Life blood of your motor... my two cents, Matt

[01boneless]

^^ ok ill go wiseco or je lol 100-120 lol i wish there were that cheap cheapest kit ive found is 149 ? lol do wiseco even make a 85.5 i cant find it?

[CJM]

Namura is cheap junk, athena is actually very good and wiseco and JE are top along with CP.

Me, I spend my cash where it counts-pistons and gaskets. Either fails your F'd so spend the money on good stuff now before you gotta redo it later.

[01boneless]

ok now im set on wiseco (cheaper than je and just as good) but i cant seem to find them in 85.5 (402) now i dont want to go to 407 because of more heat but my question is will there be enough heat to worry about because i dont want to half to instal a fan (unless i have to)? also my dad says ill notice a small power increase with the wiseco 11:1 407 piston true? becuase i though the power came from compression not the bore size unless its like 416 426 or 440? (if so that would be good :D )

[CJM]

Your still adding displacement of course, but its not that much to brag about, compression of course is where the power is. Your boring it .20 over, its not much at all. Heat only becomes an issue when you dont jet it properly and race it-it never gets cool enough cause your constantly on it. I never had an issue with my 416.

btw I found you one on ebay. http://cgi.ebay.com/ebaymotors/WISECO-PISTON-KIT-020-99-07-TRX400EX-400EX-11-1-85-5mm-/390343939450?pt=Motors_ATV_Parts_Accessories&hash=item5ae24fd57a

Thats honda of east toledo, I believe they are a site sponsor so it might be worth it to call or ask them about a discount.

Remember something, when you set up where the ring gaps will be do them like this: (imagine your staring at the piston from the top) the top, the arrow faces towards the front (to exhaust valves). Set the first rings gap to be at the arrow the second 180 degrees of that, the oil ring to a mid point somewhere not near the first two gaps, the middle oil right antoher spot away fromt he gaps and set the last ring 180 degrees from the first oil ring. This ensures its all gapped properly and you dont have any issues. Read the directions to the piston too!

[01boneless]

ok thanks cmj will i have to rejet

[CJM]

little bit, but not to much, maybe 1-3 sizes main.

[400exrider707]

No one here can tell you if you need to rejet or not, partly because we don't know if your current jetting is even correct.

I've also put in high compression pistons before and had to go DOWN in jet sizes. If it seals really well, it's going to put more of a vacuum pulse on the carb and actually pull more fuel in already.

Your best bet is to put the piston in, then ride it and check the plug.

[01boneless]

^^ ok thanks bro