[11:1 piston for 300EX] - ATV Riders Forums - Honda, Yamaha, Suzuki, Kawasaki, Polaris, CanAm, Arctic Cat, Kymco ATVs

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11:1 piston for 300EX
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Posted by: hondapro300EX

Wanted to know will I tell a big difference over stock with a 11:1 piston. Or would it be best just to get a 350 kit from gt thunder.

Posted by: MX300ex

o ud tell...id sugest getting a port and polish to go with it

Posted by: rollie

From what ive heard Port and polish doesnt really do much for 300ex's, i have a .80 piston with a 12:1 comp ratio and a .335 web cam, that made a BIG difference

Posted by: Sjorge300EX

i just put a one over bore 11:1 in my 300ex and it has so much bottom end compared to before.

Posted by: humblesquirel21

how do u like that .335 cam is it reliable im putin in a .336 nd am wryed im gona have fits when i try to get it to idle

Posted by: humblesquirel21

hey honda pro how did that bumper lien up being that its from a 400ex and the msr with hot start how did thast work im doin similar stuff to my 300

Posted by: 300ex73

quote:
Originally posted by rollie
From what ive heard Port and polish doesnt really do much for 300ex's

I've always been told just the opposite on this one. Most engine guys I've talked to that have worked on 300's say that a good port and polish is one of the first things to look into doing. From what I've been told, the heads on 300ex's and 250x's are pretty restrictive.

Posted by: Cody_300ex

quote:
Originally posted by 300ex73
I've always been told just the opposite on this one. Most engine guys I've talked to that have worked on 300's say that a good port and polish is one of the first things to look into doing. From what I've been told, the heads on 300ex's and 250x's are pretty restrictive.

He is right, it helps tremdouslly. I have rode them stock porting and ported. I reccommend doing some research and do it yourself cause anywhere you send it dont expect it back for another 2 months.

Posted by: hondapro300EX

Thx guys!

Going to send if off to four stroke tech this week. I would do it myself but i ain't feelin as lucky as i felt with my pocket bike. By the way pocket engine blew up. So i'll stick with a profeesional doin it.

But all info was helpful. I had to put some spacers on the top mount bumper and the hot start is just putting the reverse in there. Simple stuff but i recommend getting that foot shifter mod for reverse. So much easier. Can get it on ebay or make your own.
Thx alot. Oh by the way what do ya'll think the best cam for bottem end and mid for the 300EX
Thx

Posted by: chapmanmd

As far as cams go, I am partial to Megacycle cams. I know that Web Cams makes a good one as well. I would check with FST before sending your stuff to make sure that Mickey is back to work.

Posted by: bradley300

or just send it over to gthunder for a 350 kit

i had the first one, and it was great!

Posted by: chapmanmd

Cool on the GT Thunder. Im doing the Powroll stroker now too. Should be cool.

Posted by: bwamos

Agreeing with the above guys. Headwork does wonders for the 300ex.

Cam, 11:1, headwork, pipe, filter, are almost a must.

Big bore is optional.

A stock bore 300ex (287cc) with good headwork 11:1 piston and a cam will smoke a 330 w/o any headwork.

Remember that head was built for the 250x, and it's was designed by the same lawyers that put on that retarded reverse mechanism.. lol.

Posted by: chapmanmd

Bwamos is right on there. Anyone that tells you that GOOD porting and polishing, big valves, and such on a high compression, piped 300ex/250x wont make a difference is smoking crack.

Posted by: Cody_300ex

quote:
Originally posted by chapmanmd
As far as cams go, I am partial to Megacycle cams. I know that Web Cams makes a good one as well. I would check with FST before sending your stuff to make sure that Mickey is back to work.

He Is not. I read somewhere on here Laz at GTThunder isnt taking anything as of right now. I would try rocky ridge racing

Posted by: chapmanmd

quote:
Originally posted by Cody_300ex
He Is not. I read somewhere on here Laz at GTThunder isnt taking anything as of right now. I would try rocky ridge racing

Good Call Cody. Im sure that Sparks is backed up a couple months too. Im praying for Mickey's recovery.

Posted by: hondapro300EX

Well i found another place. He wants 100 plus 10 shpping for a mild port and polish. And 200 plus 10 for extreme. Ain't bad.
Will tell if i tell huge power difference. Which will be alot!!

Posted by: bwamos

quote:
Originally posted by hondapro300EX
Well i found another place. He wants 100 plus 10 shpping for a mild port and polish. And 200 plus 10 for extreme. Ain't bad.
Will tell if i tell huge power difference. Which will be alot!!

I'd make sure he has and uses a flow bench. Seat of the pant's port work is a waste of money.

Posted by: chapmanmd

$100 doesnt exactly instill confidence that there is a flow bench involved. I dunno...

Good Luck!