piston question

[tmatthews4]

would adding a 13-5-1 piston require a programer if everything else was stock?

[bigbad400]

yes. and remember this. there is no replacement for displacement. meaning if you want more power go big bore not hi compression. hi comp has a huge toll on valves and piston rod. and could result in a huge disaster inside ur motor unless u are gonna redo everything id only go with a bigger piston. remember everything works in unison and if u chage one factor you need to look at were its gonna have the most affect.

[Limited Z_400]

Originally posted by tmatthews4
would adding a 13-5-1 piston require a programer if everything else was stock?
What year is it?
Do you race?

[LTR450_#67]

I think a heavier piston will take more toll on an engine than a higher compression piston. Either way you'll need fuel controller.

[bigbad400]

the piston will be like a couple grams more than stock in a big bore application, 450cc to 507cc for example is 1.463 grams more than the stock.

when you go hi comp your stressing everything thats under compression.

i built many machines over the years, the dif between a stock 400ex piston and a 440 big bore piston is .398 grams more weight. for that much more displacement. when i put a 440 12.5:1 comp piston in instead of a 9.8:1comp like stock it broke the rod. others have lost valves due to to much compression..... do what you do but i advise a HD rod if your gonna do the hi comp at least.

[MXin700R]

If everything thing else is stock you wont need a fuel controller. The piston change will not change the fuel amount requirements, just the fuel octane will change. Now if you change the size of the engine when changing pistons then yes, the amount of fuel requirments will change accordingly. I do however recommend a fuel controller for the simple fact that more than likely you will do other mods like intake/exhaust/porting/cam timing later on and it will be an investment.

[09RappySe]

Originally posted by MXin700R
If everything thing else is stock you wont need a fuel controller. The piston change will not change the fuel amount requirements, just the fuel octane will change. Now if you change the size of the engine when changing pistons then yes, the amount of fuel requirments will change accordingly. I do however recommend a fuel controller for the simple fact that more than likely you will do other mods like intake/exhaust/porting/cam timing later on and it will be an investment.

Correct!!

[tmatthews4]

good replys from everyone,thanks,we have two bikes that we are going thru the motors on,the first was fully built on top,atp head,plus one valves,atp intake cam,pcv,fuel atv intake,athena 493 bb,that one broke the rod twice this year and ruiened both lower ends,the other is completly stock and after reading big bad's reply i think we will leave it that way,the reason for the question was because i had a 13-5 piston laying here new but i think i will stay stock on this bike,as for the other bike looks like in order for it to be reliable i need to beef up the bottom end,sorry for the long post ,thanks for the help