pipe comparison

[bigborebanshee]

Im currently running a vitos 68mm big bore cylinder(10 port cylinders) set up by vitos for a 4 mill crank

I just cleaned up the transfers and polished the exhaust port,other than the porting that come on the factory big block,thats it.Compression is 160 psi

 

I run a 30mm oko,stock reed cages with vitos carbon fiber dual stage and an FMF gnarly pipe.

 

Are the FMF pipes holding this engine back a little? a lot?..would it be better to go to a shearer or CPI at that point?

 

The bike is a beast on the mid range and bottom,it walks 4 strokes out of the hole,but its almost too torquey for the woods,i rarely ever see past 3/4 throttle..

 

Will a CPI or shearer retain some of the bottom end or will i just be shifting the powerband further up the RPM?

 

Would a small bore CPI work better than the big bore pipe to retain some low end torque?

Edited November 19, 2009 by bigborebanshee

[gregrob]

Im currently running a vitos 68mm big bore cylinder(10 port cylinders) set up by vitos for a 4 mill crank

I just cleaned up the transfers and polished the exhaust port,other than the porting that come on the factory big block,thats it.Compression is 160 psi

 

I run a 30mm oko,stock reed cages with vitos carbon fiber dual stage and an FMF gnarly pipe.

 

Are the FMF pipes holding this engine back a little? a lot?..would it be better to go to a shearer or CPI at that point?

 

The bike is a beast on the mid range and bottom,it walks 4 strokes out of the hole,but its almost too torquey for the woods,i rarely ever see past 3/4 throttle..

 

Will a CPI or shearer retain some of the bottom end or will i just be shifting the powerband further up the RPM?

 

Would a small bore CPI work better than the big bore pipe to retain some low end torque?

 

 

I dont know how the cyls are ported but yes the FMF's are holding back. They would hold back a good running stock stroke.

 

I also know you DONT want big bores on an engine that size.

 

Try some CPI or Shearer small bore inframes and you will love them. I would go CPI if you want a little more down low. They come on a little earlier than Shearers.

 

Dont forget to rejet! It will be using more fuel on the topend.

[bigborebanshee]

I dont know how the cyls are ported but yes the FMF's are holding back. They would hold back a good running stock stroke.

 

I also know you DONT want big bores on an engine that size.

 

Try some CPI or Shearer small bore inframes and you will love them. I would go CPI if you want a little more down low. They come on a little earlier than Shearers.

 

Dont forget to rejet! It will be using more fuel on the topend.

 

I would have to check the port timing.Im sure Vitos does not do much on those cylinders other than raising them to match the 4 mill,it does have the triple exhaust port though.The transfers definitely were untouched.

 

i just don't want to lose too much bottom,but if we are talking 10 or more HP peak,i don't care where it peaks