what is the bore on350x to turn into 500cc

[ronniecarrigg]

what is the diffrence in 12/1 ratio to 10/1 any one with extensive knowledge on bore and piston please give some info trying to learn more about my little engine

[camoweasel]

I seen your previous ad but didn't respond because, I was unsure what you were asking.

The difference in 10:1 and 12:1 has nothing to do with bore size. That is simply, the amount of compression each piston has. Higher compression pistons have domes forged onto the piston crowns to simply, push the air/fuel mixture harder against the top of the cylinder. The higher the compression ratio, the harder the air/fuel mixture is compressed within the cylinder. Now, the more you compress the air/fuel mixture, also increases your engine's octane requirement. Generally a 10:1 piston, should run fine on 93 octane pump gas. A 12:1 piston will likely require the need for higher octane fuels such as race fuel, 100LL av gas, pump gas with a tolune mixture.

As for boring, you should only bore the cylinder enough to clean the scuffs and scratches on the cylinder wall. I believe Wiseco sells pistons in OEM bores all the way out to .080 oversize bores.

And you can not a bore a 350x jug to 500cc. Not enough meat to do so. Companies like Powroll make a big bore and stroker kit that gets you up to around 490cc i think??

[2Tim215]

What are the 500X's using that I have seen on Youtube? Are they starting with 400EX or 450R motors? Just curious!

[blkstangman88]

powrolls kit increases the 350x to a 430x. which is a 6mm stroked crank and a 86mm forged piston.

or you got kustom crafts big bore kit which doesnt use a stroker, just a 92mm piston and makes a 452x

then you can go extreme and use kustom krafts big bore and Powrolls stroker crank along with a 3mm plate under the jug for a huge 492x.....basicly a ticking time bomb

[greenhuman]

I don't know about the time bomb thing.
Everything in these engines is big and beefy so they do handle big mods easily.

[SWIGIN]

I know guys who built 350x motors well over 500cc but they are time bombs. My favorite big bore stroker is a 6mm crank with 89mm XR500 piston. This makes a 460 and they hold up well.

[Chazz of Blades]

Or take a CRF 450r motor and pop in there.......

[big specht]

powroll did make a 9mm strocker for the 350's but not any more. The 500cc ones are fun to ride but hard on the right foot/boot.

[350XJEDI]

xr600r moter?

[bcredneck]

if you whant a motor that big put a bigger motor cause a 500cc topend will destory the bottom end that was desgined for
350cc honda made these to last but not with almost twice the power and you would probly kill a clutch in a day

[Hurricane635]

I disagree with the time bomb thing, I've been building these engines for years now, and our current 350x is a 535cc has been hanging tough for quite a while. I have 96mm big bore kits for sale with no core. Price is $400.00 + shipping. You need to have your crankcase bored also, which we do for $100.00. The 96 kit gives you 492cc. The 535 kit has a 6mm stroker.

[big specht]

I head the counter shafts don't like that much power in any gear above 2nd

[ronniecarrigg]

i imagine you have to do valve or head work when you soup it up like that right?thanks for help guys might keep it stock but i am going to powdercoat engine since its out

[ronniecarrigg]

if you change the stroke will the piston hit the head or come up short just trying to understand everything what exactly does changing stroke do

[Hurricane635]

Well, I guess anything can be broken, but I use all the gears in my 535 with no problems so far. We don't race it but we ride it hard, 350x motors don't like to rev anyway, and even less with a stroker, so we added 1 tooth on the countershaft, would like to add 2 but the case saver would be too thin, maybe a 36 rear sprocket. Powroll shortens the con rod 3mm to make up for stroke. As far as head work goes a basic port job and stock valves, and carb worked well, but 2mm oversize valves and a 38 mikuni flat slide really woke it up.