Porting and Pipe Question

[REDTHUNDER]

I have a 2000 CR250 that I recently had Eric bore to 265 with mo-better everywhere porting. I called the other day to inquire as to what pipe would work best for this application and he recommended the FMF Gnarly. He said it works better because it holds heat in the exhaust better. This makes sense to me but I was wondering if, or how much top end I would lose? Additionally, I am wondering if it would benifit me to chage the pipe at all? (It currently has the SST on it)
I was reading Eric's book and he mentions that retarding the timing a bit helps with top end but is a little flatter on bottom. I was thinking retarding the timing with the gnarly pipe might be a good comination for overall improvement.....is that a dumb idea?

Just so you know:
I would consider myself an intermediate rider and I primarily ride motocross and to a lesser degree offroad trails ect.

Also, I was looking at my cylinder when I got it back from Eric. Other than epoxy in a couple of locations and some apparent work on the exhaust valve, I could find no evidence of the porting. Is this correct for the Mo-better everywhere porting? It makes me wonder if we had some kind of communication mix up and he ended up just boring it.
He overbored my CR80 with the same porting, but the porting he did was evident on that one.

I realize my ignorance on this matter so I figured I would ask.

 

[Studboy]

He did port it with the overbore, he always does, you just may not be able to see it because the changes are really miniscule.

The gnarly's still have decent topend, and retarding the timing will only help. The trick with the timing is to experiment until you get it how you like it. I'm not sure though if it would be worth it to shell out the money for a new pipe if your other one runs decent.

 

[REDTHUNDER]

Thanks, I appreciate the information. It's nice to know that there is always a good place to have my lame questions answered by those who are in the know!

 

[blackjack]

Also, I was looking at my cylinder when I got it back from Eric. Other than epoxy in a couple of locations and some apparent work on the exhaust valve, I could find no evidence of the porting. .

Do you remember where he added the epoxy, was it in the r transfer ports at the base of the cylinder or at the cylinder port itself?

Thx

 

[Rich Rohrich]

Also, I was looking at my cylinder when I got it back from Eric. Other than epoxy in a couple of locations and some apparent work on the exhaust valve, I could find no evidence of the porting. Is this correct for the Mo-better everywhere porting .

The reason you can't see "evidence" of the porting is due to the fact that the porting is done BEFORE the replating of the cylinder after it is bored to the new oversize. The plating covers the machine marks left by the porting tools. The nickel content in the Nicom plating process is high enough to make it very difficult to port the cylinder after the plating process. You would have to measure the port area before and after the porting process to determine the changes that were made.

Do you remember where he added the epoxy, was it in the r transfer ports at the base of the cylinder or at the cylinder port itself?

Thx

Epoxy is used in the transfer port windows in the cylinder to alter their volume and direction.