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cacustom
02-23-2005, 10:10 PM
I wanted to get a 300ex bore kit with 11:1 conpression ratio but the guy at the shop told me that i would have to change the crankshaft and eventully the cylender because those parts are to old to run with a bigger piston and that they will eventully wear down.

My question is has anyone bored their 300ex? if so did you have to change the crankshaft and the cylender? and does it run well?
bradley300
02-24-2005, 06:21 AM
how old is the quad? high compression does puit alot of stress on a motor, i doubt the crank need replaced for it, but it would be a good idea to use a heavy duty rod
cacustom
02-24-2005, 08:32 PM
the year of the motor is 97
beak7707
02-24-2005, 09:20 PM
That guy is nuts. I ran 11.5:1 in mine and had no problems at all. There are people out there running 350 big bore kits that arent replacing the crank. If you are using the stock cylinder I think the highest you can go is 305 you will be fine. when it is tore down check your rod and bearings if they look good go for it.
cacustom
02-24-2005, 10:22 PM
Would you recomend replace my rod with a new one? mine is a 97 so its pretty old.
bradley300
02-25-2005, 10:41 AM
if you have the xtra money i would replace the rod, but really until you get more compression the stocker should be fine.
cacustom
02-25-2005, 12:36 PM
I have another question.... If i changed my compression ratio to 11:1 the guy told me my electric start wont work bc it wont have enough power to turn my motor over, so what do i do? install a kick starter? If so how much would that cost?
m250r
02-25-2005, 01:26 PM
what you should really do is find a different guy to do work for you:rolleyes:

your 300 WILL start wiht a 11:1 piston its just that the starter will be slowed down a tad. + you cant install a kickstarter without some SERIOUS work. get the 11:1 piston and you will be happy with it
bradley300
02-25-2005, 04:27 PM
i agree, this guy obviously dosent know jack about a 300ex, send your motor to GThunder
cacustom
02-25-2005, 09:15 PM
does GThuder have a website?
m250r
02-25-2005, 10:00 PM
GT THUNDER (http://gtthunder.com/)
bradley300
02-26-2005, 07:31 AM
get laz's number off his site and call him. he is the most knowledgable engine builder i have ever heard of. you will love his work
sleeveslave
02-26-2005, 07:50 PM
CA--you have a pm.
cacustom
02-28-2005, 10:05 PM
Thse are questions for people who own a bored 300ex. Where did you get it done? how much was it altogether kit and installation? what did you get done?
bradley300
03-01-2005, 05:57 AM
i paid a little less than 1500 for a 350 bigbore. this was sleeve, piston, case machine, porting, valve job,HD rod, crank rebuild, HD cam chain, labor and any other parts need to rebuild a locked up motor (ran with out oil)
this was from gthunder, i sent it in june and had it back in mid august