Over Size Pistons & Jetting

TLRam1 · Post by **TLRam1** » Thu Nov 13, 2008 1:20 pm

In going half OS on my GT380 will stock jetting need to change? If not, on any bike (T500, 550, 750 etc.) does jetting need to chg when going OS?

Arne · Post by **Arne** » Thu Nov 13, 2008 7:29 pm

What's os?

If it's some form of fuel or gasoline other than 85 to 105 octane then I'd say yes you'd have to rejet.

Good luck! Arne

TLRam1 · Post by **TLRam1** » Thu Nov 13, 2008 8:04 pm

OS = Over Size

Wayne Meuir · Post by **Wayne Meuir** » Thu Nov 13, 2008 8:29 pm

I doubt that boring will create a need for jetting changes unless you change the intake or exhaust.

Wayne

Arne · Post by **Arne** » Thu Nov 13, 2008 10:23 pm

Wayne Meuir wrote:I doubt that boring will create a need for jetting changes unless you change the intake or exhaust.

Wayne

+1, no change for the jets - sorry I guess I should've read your title!

TLRam1 · Post by **TLRam1** » Thu Nov 13, 2008 11:20 pm

Arne wrote:
Wayne Meuir wrote:I doubt that boring will create a need for jetting changes unless you change the intake or exhaust.

Wayne
+1, no change for the jets - sorry I guess I should've read your title!

Arne, I changed the title because of your post.

rngdng · Post by **rngdng** » Fri Nov 14, 2008 12:43 am

Nope, shouldn't require a change.

Lane

Coyote · Post by **Coyote** » Fri Nov 14, 2008 8:57 am

The facts are, you started with 371cc's. Refitting the engine with half over pistons brings the engine displacement to a whopping 378cc's. Still not a true 380.
I found a handy online calculator. See my post 'The Real Facts' is this section for a link to the calculator.