Anybody know what size (50mm....58mm...) the stock 09 throttle body is? P/N is 27685-08A

 

50mm 08-later

 

Thanks Dawg!

 

True or False...With a 08' having a 50mm TB, I can't believe anything larger is needed for a 103 build. (?) Meaning no real gain is accomplished by changing it out????

I have NO experience with F.I. My basis is from carb bikes. My 95" FXDWG3 and BIL 116" SG has a 45mm Mukuni and it's more than enough fuel.

 

50mm is fine for 103 cubes, no need to go bigger till 113+

 

It depends on what all you are doing with the build. If you are putting money into a good headport, it might be worth it to at least have the TB cleaned up a little. You don't necessarily have to replace it with larger. I do know the HD stage IV 103 uses the SE 58mm throttle body.

 

Now on my 103 build on my personal bike. We did the heads and were going to up grade the intake to the screaming eagle and on the flow bench, with our porting the screaming eagle actually flowed less. So you never know, in my opinion if you can port yours or get your hands on a bench, you'll know for sure.

 

Bigger isn't always better when it comes to TB inlet size. Along with an increase in TB diameter comes a reduction in air velocity. This is why in some cases bigger results in decreased performance.