I just recently compared the two cylinders on my 250R and the results were surprising to say the least. I've had my CT 310 Pro-X cylinder for awhile now and was very pleased with it. But since I installed the cylinder as a kit with midrange pipe, FMF Ram Valve, reed block spacer and bigger Keihin PJ carb, I couldn't help but be curious how the mods on the stock cylinder would do. In other words, how much difference did the $900 cylinder actually make. The Pro-X cylinder, while a thing of beauty, does very little. The only difference is the stock cylinder has a little less torque and revs a little faster while the Pro-X cylinder is just the opposite. I had the Pro-X ported for midrange by CT and there is quite a bit of difference in the ports. I must say that I was quite dissappointed. Anyone else have the same experience?

 

It is a well known fact that CT does a very poor job of porting. In fact they hardly port at all. They only "match" the sleeve to the barrel. Ask someone who has an esr, sparks, macdizzy ect... ported cylinder how they like it. You will be shocked to say the least. As I write this letter Macdizzy a.k.a Rick, is porting my pro-x 310 cylinder. I cant wait till i get it!!!!
sean

 

I also bought a 310 pro-x kit from ct that was supposedly mx ported but it is only good for top end. It is like a lightswitch-no low end power at all. I hope to get it rectified this winter. I just hope the ports are not messed up already. Any esr comments out there on their 310 pro-x cylinder work? Thanks

 

I have an ESR 310 with TRX9 porting and the mid-range/top end pipe. Also has a 38 mm Air Stryker and a CR intake, reed cage and reeds. I run a K & N with the air box lid off. The porting is a true work of art, and it is very, very fast. It has great power and is very ridable from mid range on up to a crazy top end.
I also have an 86 that has a Duncan ported motor. It runs a Delta V-force type intake and has a Paul Turner race pipe. It had a stock carb taper bored to 37 mm, but it just did not pull off the bottom like I wanted so I put a stock carb back on. It runs very good. Much like the ESR motor, just less everywhere. It is a fast bike, but the 310 is head and shoulders above it. With all else being equal, I firmly believe that there is no replacement, for displacement.

 

it just seems to me that a well ported 250-265 is just about as fast as a 310, and revs faster too.