.80 bore on 300EX worth-it or not?

[300eXTraILRyDeR]

I read that a .80 bore will bring a 300ex around 298cc's. How thin will the sleeve be and how reliable will the quad be? Most importantly will i get a noticible gain? This mod will be done by itself. I allready have intake and exhaust so i am guessing this is the next step. thank you

[JDsBusa]

I am looking to do the same thing to my 250x, someone told me a 250x bored .080 will make it a 298cc? I don't know, I haven't found any real tangible info on the bores to final cc.

.080 over goes to like 304.5 cc, just multiply 1.08 x 282

[NJ300ex]

I think you got that from what i posted. If you want to do mods to your 300ex talk to 465stroker. His wife has the nicest 300ex you will ever see.

excessive heat,no good,but i would just go with a tc racing set up.they have a piston kit,valve sring kit with cam..the new cam allows the valves to stay open longer and the piston has pockets for the valves to seat now that they push down father,and it doenst effect your compression,which is a good thing to stay away from modifiying on the 300ex,the crank will need to be changed if you go with more comp,and more heat will follow.

[stocktires]

My dad just rebuilt his 300ex with a .50 over pro-x piston and the power isnt really noticiable unless the quad really needs a bore! make sure and get a high compression piston!

[hetrick425ex]

mine is .80 over and it does add noticable power, we used TC cam in mine, tom knows what they are doing, it does add alot of heat if i were you i would get a oil cooler, i went with a 12:1 arias piston its up to u if you want that high compression because it is alot for the battery to turn over if you do this add hd valve springs and replace the valves if neccacary, make sure when you do all this u get have a aftermarket air filter and pipe and you will be ooooo soo very pleased if it works right and if you add hp you add strain on you engine get a hd crank bearing and a hd clutch kit... i used white bros with hb springs, DO NOT USE BARNETT!
just my 2 cents
later

[chris29]

I have a 300ex and its been bored .80 and you can tell a big differance. If saver to bore it .80 so that if you ever seize a piston you can bore it one more time .120 over.

[330EXman]

how come you say dont use a barnnet clutch. do you have bad experience. if so did you have the kevlar clutch kit with heavy duty springs

[hetrick425ex]

yeah we have had so many bad expierences with them we dont even run or sell them anymore...we use whitebros for 4-strokes
later

[MR. HONDA EX'S]

I've got a barnett with stock springs in my 300, and no trouble yet. My cuz's 416 ate up a whitebrothers clutch and springs in 2 weeks. He put in stock honda and no trouble. I won't buy a wb's clutch ever. That's just me.

[outlaw319]

Here is a little formula to help you guys figure out boring sizes:
1st_for every .20 over you get .5 mm
2nd_a stock 300 bore is at 74 mm
so boring .80 over would make your new bore at 76 mm.
the stroke for a 300 is at 65.5 mm
get a calculater and do this:
bore x bore x stroke x .0007854 = displacment(cc)
(74 x74 x 65.5 x .0007854 = 281.70) round the .7 (282) stock
(76 x 76 x 65.5 x .0007854 =297.13)round the .1(297)bored .80
Hope this helps! this is a thing I wish that I knew years ago!