Cranking up the CCs but sticking to pump gas?

[Lorduss]

hey guys,
im considering going bigbore, but i got some questions,
is 440 the biggest i can go to sticking to pump gas?
do they make a bigger piston ? race gas is just a pain in the ***, id prefer not using it, 92 octane is all i ever use in my bike so it makes it easy to sifen out of some thing when you need to.

i want the best preformance for my gas, because i realise timing and compression are closely related to preformance.

of corse im going with other mods, cams, carb, exaust, but i want a good base to start off, the piston, the bigger the better,

any tips ? Thanks

[Nausty]

Originally posted by Lorduss
hey guys,
im considering going bigbore, but i got some questions,
is 440 the biggest i can go to sticking to pump gas?
do they make a bigger piston ? race gas is just a pain in the ***, id prefer not using it, 92 octane is all i ever use in my bike so it makes it easy to sifen out of some thing when you need to.

i want the best preformance for my gas, because i realise timing and compression are closely related to preformance.

of corse im going with other mods, cams, carb, exaust, but i want a good base to start off, the piston, the bigger the better,

any tips ? Thanks

you can even have a 505 run on pump gas you are just gonna have to run 10.5:1 or 11.5:1 compression I don't remember. Thats 92 octane. The higher compression piston your run the more power your gonna get and higher octane gas. I know the sparks 465 is not stroked and is just running a sparks sleeve. If you plan on doing all that chances are its gonna cost ya. Check out sparksracing.com and click on 400ex and you should see around what its gonna cost ya.

[oynot400]

It is not the cc that determans the type of gas you run. It is the compression ratio. If you stay under 11:1 you should be fine any thing higher will require race fuel.

[Lorduss]

i realise its compression ratio, but i know alot of kits are 460 and such, are basicly a 440 stroked out,a longer stroke also increases compression right?
505 kit i belive is achived by changing the stroke, i highly doubt they make a 505 with stock stroke.

stroke does change compression right ?

[MIKE400EX]

Everything else being equal, an increase in stroke alone will also increase the mechanical compression ratio. Along with an increase in stroke you need to either, use a piston with a shorter deck height, raise/space the cylinder up, or use a shorter connecting rod. If you opt for a different piston, (the most practical way to go with a 400EX), then you can order one for pretty much any compression ratio you want.

[Lorduss]

TTT.

Who makes the biggest piston i can put into my bike ? sparks ? weiseco only makes a 440 CC, id like to go higher if i could,

whats the best compression to run with 91 octane ?
i rember reading only using 92 octane in the manual but high preformance fule at the gas stations around here are 91.

not the max compression i could run, but what would be the best preformeaning ?

are you guys saying there is a 505 kit for a 400EX????!!!!! that is friggin awesome!!!!! HOW MUCH!!!!! i MUST have it!

[Rastus]

Ask CHadEXer, or PM him. Or, go straight to TC :)

[TRX250EXER]

FST makes a 500ex. 505 is the biggest Ive seen. And yes if you want to run race gas do not go over 11:1. a 10.8 would be about perfect with no complications. I wouldnt recommend going over 440cc just by boring it. the sleeve is gonna be too thin and not be as reliable.

[Nausty]

Originally posted by TRX250EXER
FST makes a 500ex. 505 is the biggest Ive seen. And yes if you want to run race gas do not go over 11:1. a 10.8 would be about perfect with no complications. I wouldnt recommend going over 440cc just by boring it. the sleeve is gonna be too thin and not be as reliable.

sparks 465 is just a bore with one of there sleeve and I heard they are pretty reliable.

[Nausty]

Originally posted by Lorduss
TTT.

Who makes the biggest piston i can put into my bike ? sparks ? weiseco only makes a 440 CC, id like to go higher if i could,

whats the best compression to run with 91 octane ?
i rember reading only using 92 octane in the manual but high preformance fule at the gas stations around here are 91.

not the max compression i could run, but what would be the best preformeaning ?

je probably. Check out sparksracing.com

[FullBore52]

sparks gets a JE piston that is 92mm for the 465, then they drop a 6mm stroker crank in for the 505. FST gets their 500 by getting a 91mm piston and then dropping a 7mm stroker in. FST's 500 will NOT run like the sparks 505 because of compression and revs. Chad Duvall's bike is only 11:1 compression...hes only running a 162 main in a stock carb...how much horsepower can he POSSIBLY be making with that? Not very much..I would guess. the Sparks 505 can be 12:1 or 14:1 compression and runs an FCR41 or FCR39 with probably something like a 195 or 200 main...the way I look at that, a small jet means its not flowing much air...so even though i am roughly 20cc short of that FST 500, I SHOULD be making quite a bit more horsepower....funny how those things work. FST's 500 seems like it would be a beast, but its really not.

(sorry, I just had to vent about FST a little...I really am not impressed with them, lol)

You could go bigger than 505 if reliability wasnt a concern, just take sparks' 92mm sleeve bore it to 93 or 94...drop in their stroker crank, and you have a 516EX with the 93mm, and a 527EX with teh 94...sounds fun huh?

[Lorduss]

hehe, TC happenes to be 15 min up the 605 freeway for me, i should stop by, on the way back i should hit up trinity, there about the same distance away on the 91.

i realy want reliabliltiy, i dont want to have to rip my engine apart and replace ****,

so sparks makes the 465 that i can run on pump gas ?

"FST makes a 500ex. 505 is the biggest Ive seen. And yes if you want to run race gas do not go over 11:1. a 10.8 would be about perfect with no complications. I wouldnt recommend going over 440cc just by boring it. the sleeve is gonna be too thin and not be as reliable."

dont you mean "if you dont want to run race gas" ??
10.8 is perfect?

can i have a engine builder build it to my specs?

trinitys 460 kit is just there 440 with a repositioned crank pin, so the more CCs they push by doing that the higher octane id have to run ?

[FullBore52]

Sparks really pushes for you to run alcohol, but I'm sure you could talk them into getting you a lower comp piston.

As far as comp ratio goes, mine comes out to 10.81:1 and I run 20%-40% vp-c12, it runs very good compared to straight pump gas- 92 octane.

Mike400EX- We've run a similar setup for quite a while and I'm looking into suspension. How do you like your shocks compared to stock? Thanks :)

[TRX250EXER]

yeah, that was a miss print I ment to say pump gas. sorry got mixed up. but the I'd rather have the 500 than the 505 just because of that. you can still run a lower octane fuel. if you read up on his 500ex you would see why they still used a stock carb. I forgot what it said but there was a reason. and if you would put in the same compresion piston in the kit I bet the 500 would actually have more hp. stroke cc have more power than bore cc. The 500ex has a longer stroke right? and you could still put on a bigger carb too right?? I dont know but that is just my guess. I can see what your saying tho on the KITS, and what they come with.