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View Full Version : New 503cc 400ex bore kit



400exrapes
08-06-2007, 10:56 PM
on the 400ex forum theres talk of this new 503cc big bore kit for the 400ex does anyone have a dyno of this ? i know one guy has an almost stock 400ex with the huge bore in it he just posted btu i cant find him

Big - D Racing
10-13-2007, 08:41 AM
that bore would be ipossible on the 400ex atleast with the stock cylinder. It would bore it out way too far and couldn't be cooled. It run super hot and break real quick. There is a 500 kit ut it is a combo bore and stroke. I believe it is a 440 bore (89.00mm) and a +4mm stroke kit put you right at 499 I believe. Now if you do the 89.25mm bore it will take you to 503. That is probably what you are thinking about and is the highest I have ever hear of. Back in the day when the 400ex was the hottest quad Four Stroke Tech did make a bolt on top end that was a 500cc liquid cooled. That was a totally radical design that bolted to the stock bottom end. He stopped making them a while ago though. I think they ran for like $3000

Wheelie
10-13-2007, 09:01 AM
A 440 Bore with a +4 stroker is a 460. I believe the 503 kits are a 92mm piston and a +7 stroker.

400exrapes
10-13-2007, 10:24 AM
well if any of you find someone with one let me know i wanna see how those things perform

browng31
10-18-2007, 07:15 PM
A guy on another popular site's name is Chad502ex, he might be on here too, he built them and he probably has some dynos.

400exrapes
10-18-2007, 08:36 PM
thanks ill look that up now.

Mickey Dunlap
10-27-2007, 09:56 AM
I still build the 500 kits. We start off with a 90mm piston and a 7mm longer stroke with 4 over bores up to 500cc with a 91mm piston. The 90mm bore is a 490cc.

LT250_JOE
11-14-2007, 04:52 PM
Originally posted by browng31
A guy on another popular site's name is Chad502ex, he might be on here too, he built them and he probably has some dynos.


READ "GETTING CLOSER TO 60HP" POSTS CHAD 502EX IS ALL OVER IT.

Benjithx
02-07-2008, 05:09 PM
How do you keep something like that cool?

TURBO-530R
02-12-2008, 02:45 PM
I have a 502 for sale 8mm stroke and 90.5mm piston
Pm for info

Muddinguy
10-14-2009, 11:45 PM
whats the word on 4stroke tech's 465 big bore kit ?? isnt that getting a little thing on the cylinder walls ?

QuadCobbler
11-25-2009, 12:45 PM
"My quad's so black it could run for president !"

lmao!!!!!

05-21-2010, 09:27 AM
that is soooooooo funny

nastyracing
03-18-2011, 11:41 AM
I had a 6mm falicon crank 92mm bore which was considered a 505 tc racing built made 58hp . Torq monster loved the thing way more then new 450 and my banshee. But the dam motor would not stay together ripping heavy duty head studs out always a problem. To much compression and being air cooled would never do it again wasted lotz of money. You want more power buy a bigger bike.

TURBO-530R
03-18-2011, 11:54 AM
My 502ex has been very dependable and i run the piss out of it every time out. full weight bike 4.9 - 5.0 300 ft all day with 200 lb rider Hill climbs what ever you give it on 93 oct. I would do it again. the 92mm piston rocked to much
I run 8mm stroke with 91.5