Porting a KZ750 (4)

I'm thinking about doing some mild porting to my intakes and exhausts and I know I should really have it done professionally with a flow bench and other equipment, but are there any safe guidelines for doing some basic, mild porting without making it worse?

And are the gains even sufficient with a mild porting job to be worth the trouble?

Right now I'm running it with pods, 4-1 and gpz cams.

Thanks,
Chris

If you remove the roughness in the casting and match the boots to the ports it will make a difference.

As otakar said,try to match ur gaskets and port sizes as much as u can.U can do it with a Dremel and LOTS of sanding/polishing drums.Try to control the aluminum dust as this is a dirty job and u dont want that stuff in ur lungs.wear a painters mask. Remember the venturi effect. On the intake side, try to taper the ports slightly so the side facing the carbs is larger than the side facing the valves.. On the ehhaust side, the reverse is true.The taper should be larger close to the valves and smaller where the exhaust bolts on.Get the air/fuel mix in quick and the burnt gases out quick.Use a carb boot and marking pencil to outline what material u need to remove on the intke side and use a crush washer/marker for the exhaust side.hope this helps.bj

The venturi effect only speeds up the fluid locally in the constriction, it doesn't speed up the flow overall, the conservation laws prohibit that.

Basically what you need to do is reduce resistance to flow, and making your ports smoother will do this. Also, some improper porting can cause big velocity differentials across a cross section, leading to poorer flow than you started with.

chrispysaki wrote:

I'm thinking about doing some mild porting to my intakes and exhausts and I know I should really have it done professionally with a flow bench and other equipment, but are there any safe guidelines for doing some basic, mild porting without making it worse?

And are the gains even sufficient with a mild porting job to be worth the trouble?

Right now I'm running it with pods, 4-1 and gpz cams.

Thanks,
Chris

Chris,

Decarbon the combustion chambers and inspect the intake valve seats to see if they're chipping away. I've seen several like that in the past year.

They chip away from the outside edge, just outside the 45 cut. Do this before you attempt to port the head. No use in putting hours into a head that needs the seats replaced.

Thanks for the tips everyone. I'll keep an eye out for chips in the valve seats.

Send your head to a professional like larrycavan. He's the best! (I just sent him one of my heads).

DO NOT match the exhaust port exit to the gasket. You want a step there to fight reversion.

And listen to Mr. C. You can't do anything better than to listen to him.