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Big bore, hi compression, or both?

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I'm looking to get some more power out of my 06' engine and I'm considering a few big bore and higher compression options. Is it better to go one way or another?

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I'm looking to get some more power out of my 06' engine and I'm considering a few big bore and higher compression options. Is it better to go one way or another?

well, from all the motors i do and get involved with , ----personally i find ( along with lots of fast riders )--that you are better off staying with the stock bore and just building a good motor with compression , head work, cam and ofcourse cam timming and getting it working together .

i can build a 60 or a 62 hp standard bore 450 motor now that is really hard to hold onto and ride on an mx track --------( most guys will ride faster on a 52 to 55 hp motor or a stock 47 to 49 hp bike in all reality )

a 60hp 450 is a hand full to ride in the dirt ---------.

when you bore and or stroke the motor -it can be a real hard to get good cylinder fill at the upper rpm ranges , ------.

i have made big motors work but generally its alot moe money and effort than its worth :)

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I'll cetainly defer to kelstr...and say that the few folks I know that have tried the Big bore route ended-up with a bad case of heartburn and a lot of missed riding time trying to get a BB engine running properly

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When you say head work do you mean milling it doun and altering the sqwish pattern?

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When you say head work do you mean milling it doun and altering the sqwish pattern?

Honda_250f_rider is correct , -----trying to get as much flow as possable through the head at mid and full valve lifts ( with different cams ) to fill a bigger cylinder is not easy and can take alot of welding , porting and screwing around .

not to mention the different balance factor you need to attempt to employ into the crank and the different alteration to the balancer shaft to make up for the difference in the riciprocating weight of the bigger piston ------

it is not easy to get the bb where it revs good and runs smooth and makes good torque hp numbers , ------.

for the most part you are better off sticking with the stock bore and stroke -----especially for just straight up MX riding , -------( a 52 hp motor really runs way better than it needs to ----i actually ride a 46 47 hp crf 450 way better than i can ride a 55 hp motor )

the squish clearance, squish band , maximum squish velocity , and chamber voloum , angle of piston and angle of squish, -----are all terms and areas of dealing with 2 stroke motors . :)

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Well if you must athena 488 with ported head. Stage two cam and a great pipe, like the pro circuit. If you can handle it. I had one could not handle it for more than three laps.

Flyn

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I finally got to ride the 05 motor I did for ZeroFear66. 13.5:1 JE with a Stage One HotCams with a DMC pipe. I cleaned up the ports basically blended the bowls and was blow away by the mid range on the thing. Down low, felt like stock, rev the thing up just a little and you'd better be pointed where you wanna go. Its just flat angry coming off the corner at about 5500 RPM

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The 13.5:1 JE piston is definitely at the top of my short list. Any reliability problems with it? Knock, ping, parts out the side?

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My wiseco big bore 101mm piston and falicon heave crank with a hamp head is fantastic. I can ride the heck out of that thing all day long. 13 48 gearing 3rd gear starts all day long. I've learned to ride it. definitly different from a 450cc bike. mine the power comes on Strong smooth and then gets brutal. (it is hard to and I probly can not over ride my machine) but for a + 30 almost expert racer it serves my purpose. If you need a crank replacement I would do a stroker Hot rods crank. I did one recently and that is a lot of fun. With mild port work the stroker rips. Unfortunatly I used a 13:5:1 piston along with the stroker although it did not need the compression that high it is still absolutely running perfect. My advice is if you want more power go within your budget. Search out what ever parts you can get the best deal on and that should help you achieve a very nice combination. Buy a used head and re valve it your self, these are bad times and I can't tell you how many people are selling off Super Expensive stuff for Super cheap.

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my bike is 12:1 compression. runs fine on good pump gas

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