Spent some time looking at the head from my YFZ last night. Very interesting. Air flows in from the carb and gets split (3) ways and is routed (1) of (3) ways via intake valves then taken out of the chamber via (1) of (2) exhaust valves.

My question:

What exactly does porting do? The paths appear pretty simple and efficient. It just doesn't look like there's a ton of room for improvement. Actually, Mickey D. a fella @ RPM said they've both talked to Yami and agree there's not a ton of improvement to be made on the head. RPM till offers porting on the YZ450F though. Hmmm...

BTW: if you want to see the inside of your engine, take your YFZ to the dealer and have them work on it. Then, once they're done, ride it and you'll see the inside soon enough.

 

LOL! I think the flaws that normal heads have is roughness and casting flaws. I have heard that the YFZ has less of this than normal, but still has a little room for improvement.

 

With these engines that are better and better from the factory, the room for improvement diminishes. I think your logic (even though I haven't seen the YFZ ports) is probably correct. If you just go in there and enlargen the ports, you lose velocity, and can make it worse. The best bet is a guy with a flow bench who will experiment with epoxy, and find higher flow capacity while maintaining velocity and that's a large process. Those factorys, making a race engine, don't want to leave power on the table so they make these new heads flow pretty well.

This as opposed to like a set of old Ford heads, where there's big obstructions you just grind out, and exhaust ports you can't fit your finger through just waiting to be opened up.

My 2 cents worth.

 

Your's and some others like it will sway me away from spending upwards of 40,000 cents. That's not a bad exchange.

selector

 

What are you planning on spending $4K on?

 

40000 pennies / 100 pennies per dollar = 400 dollars

selector

 

I'm sure there is something to be gained from porting, Yamaha did a good job on the head but you know they didn't make it perfect. The gains may not be the kind of gains you get when you port a raptor or whatever, but any gain is a gain. You don't really know until somebody tries it.

 

OR YOU WILL GET BEAT BY THE GUY WHO HAS HIS HEAD PORTED BY SOMEONE..

 

You will be happy to know that my commission rates for advice are very reasonable.
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