TOPIC:

Preparing to switch to larger carbs I pulled the head off my 79 KZ1000 LTD so I could port match the carb holders to the head. I was going to just clean up any rough spots in the ports too. I noticed the "clean air system" has fresh air supply holes in the exhaust ports that are 9mm diameter on the outside radius of the port that looks to my amateur eye like a real turblance creator. Is it worthwhile to plug this hole and reshape that area of the port? This is a street bike, but I would like to free up power if it is available. Any sggestions on a easy way to fill the holes? I was thinking of tapping threads in the hole and making an aluminum threaded rod to screw in then peen it over and grind to the port shape needed.

Man, all that tapping and threading seems like work. For mine I just tapped it to 3/8x24, and used some set screws, but that still left the turbulece-causing hole in the port. Mine will be mostly used for touring, so no big deal. But if I were concerned about top-end I had already decided to find 3/8 aluminum rod, drill the hole out for a press-fit, then have the rod welded at the top end and grind down whatever was sticking out in the port. Welding sure seems to beat threading that much aluminum rod. For that matter, I'd think JB Weld would hold the rod in just fine, it just seems a little bit redneck. Not that there's anything wrong with being a redneck! Just my two cents' worth.

Would JB weld stand the heat?
Anybody filled and reshaped theirs?

The holes are not straight. You can not push a rod in from the top and have it come out in the port.

I wouldn't trust JB weld in the port.

We used to go to great pains to weld those holes up before porting and found no performance advantage.

Now when we port one of those heads, we tap the top side of the holes 3/8-24 and if the customer wants to block them off, he can screw set screws in the tapped holes.

Jay

i called over today looking for some tech advise,the great jay was busy but i did get to talk to the great tj;)

Thanks Jay. Yes, the holes curve to the top of the head but are sraight enough to tap for a plug of some sort. Your finding no gains tells me on my mild street motor that I don't have to bother with it. Besides the potential turbulance I had wondered if the fresh air draw would weaken the cylinder scavaging.

wireman wrote:

i called over today looking for some tech advise,the great jay was busy but i did get to talk to the great tj;)

TJ is the man. He is a racer, altho it is around corners. He has a column "Fast Times" that he does. The link is on our home page. Check it out
www.aperaceparts.com

Jay

cool,thanks again jay!