bigger piston

[ltl666devil]

on my spare 1986 atc 350x motor i wanna get it bored out bigger. the piston is at 82mm now but i wanna go a size bigger. just wondering where i could get one. the weisico catalog only goes up to an 82mm.

thanks

[Iliketogofast]

Call Wiseco, if they don't have one they might make you one.

[enduro400rider]

mabe thats as big as you can go, but i dont kno much about the 350x. if you want to go bigger maby look for a stroker kit

[fasterblaster09]

Yeh the bigger bore doesnt add power or speed.It just like a rebuild.You may have to stroke it :devil:

[prepracing]

Originally posted by fasterblaster09
Yeh the bigger bore doesnt add power or speed.It just like a rebuild.You may have to stroke it :devil:


a bigger bore does not add power ???? thats a new one on me:huh

[enduro400rider]

Originally posted by prepracing
a bigger bore does not add power ???? thats a new one on me:huh

really you dont get much power out of a bigger bore its mostly compression that gives you the power boost .

[fasterblaster09]

I dont mean that,I mnea your piston starts to get old,right?..Wll whne you replace it,you SHOULD go bigger,so its a tighter.I dunno,Thats what the guy at cpcustoms said.

[greg_gorrell]

well it all depends on how bad your cylinder is. it may just need honed but if it is scored then you will have to bore it and go to the next size. you may just be able to get away with honing it and a new set of rings depending on how bad your cylinder and piston is.

[1fastZ1slowridr]

Originally posted by enduro400rider
really you dont get much power out of a bigger bore its mostly compression that gives you the power boost .

yep compression is where its at.

[1fastZ1slowridr]

you might notice i have a 30 over piston but only cause my cyliner wall was scored or else it would have just been honed

[bwamos]

Originally posted by fasterblaster09
Yeh the bigger bore doesnt add power or speed.It just like a rebuild.You may have to stroke it :devil:

Odd.. last I checked more displacement adds more power. ;) More fuel & more air = more power.

Higher compression adds more power.. but so does displacement.

There's a reason F1 racers run an 0.56 ratio of stroke vs. bore. Lots of HP and fast reving.

Also note the bore/stroke ratio of a 450r or YZF450 vs. a utility quad. ;)

[fasterblaster09]

read here-- http://s8.invisionfree.com/Cp_Customs/index.php?showtopic=1079

[bwamos]

I agree that better porting, valve job, pipes, etc.. are all important. But increasing air flow does nothing "beyond a point" if you aren't increasing the air used.

My ex has a 47cc increase over stock + 11:1 comp.. and that is bore only.. no stroking. 47cc increase is ~17% increase in displacement.

Needless to say that is not trivial.

HOWEVER, I do agree, it is pointless without the high comp, porting, cam, valve reangle/oversizing, pipe, filter, etc.. etc..

With my mods im getting almost 2x the stock HP and about 1.4x the stock torque.

As another note.. a 0.80 over is a 15cc increase on a 300ex, 19cc on a 400ex, and 20cc's on a 450r. Not the 9cc's you were seeing on that forum.

Also stroking the crank will add low end torque.. but you will rev out a LOT slower, and lose top end performance. But you're bottom end grunt will be great.

All being said.. I do agree that he'd be better off with porting/cam/valve job, etc.. rather than boring or stroking at this point. The motor is most likley already at an 0.080 over if he's at the biggest piston size on the chart. Next step would be a big bore sleeve and piston.

[ltl666devil]

i need to go bigger cause the cylinder wall is scored pretty bad.

[bwamos]

You'll need a new sleeve. Looks like 40 over is the largest they go w/o a new sleeve.

Either get a stock dia sleeve and a new stock dia piston.. or hunt down a big bore kit.

[ltl666devil]

i think im just gonna get the powerol kit i have in my 250/350 conversion thanks for the info everyone

[bwamos]

Since you're air cooled, you'll probably wanna run 25% race / 75% premium fuel mixture in that 12:1 to avoid detonation. ;)

350x's haul. :) Enjoy.

Why go stroker though? I'm not a big fan of stroking.. most engines need a shorter stroke as it is.. lol. ;)

But, if you're racing woods.. nm. That's what the stroker is made for. ;)

[yamaha redneck]

would you trade for a 2001 yamaha blaster white and black stock motor but pro circut pipe and header and jet kit and reed spacers a brand new double o ring sealed chain and i also have the orginal chain u can have that too it also has a k&n air filter and sherrder rear tires and comes with 4 spare rear tires stock i band new set 1 slightly used if that isn't enough how much money would i have to give u too thank you for your time darius