Mike,

you need to use the copper washers. One washer goes inside the header on the bushing and one washer goes between the head and the header body. Some of the YS motors don't have the threads as deep as other in the exhaust port. So sometimes it need to use 2 internally and 1 externally.

The bushings that come with the headers now are a little longer than original ones. If you have an older header then you can use a single copper washer on it between the head and the header body. The number of washers is not important. The number needed is only to not let the bushing bottom out inside the head of the engine. I have some of the original headers that we tested running on a single washer between the head and the header body and its as good as the newer ones.

I worked very hard with Central in designing this header. I have hundreds well over a thousand flights on this header design. We have changed some things here and there to make it better but the reality is the concept is excellent and works very very well. Originally we didn't think we needed the copper as my headers were not coming loose. But when we had some more feedback and more headers got out...we realized some guys were having trouble. So a couple solutions were tried including your set screw idea. None worked well. So we got to thinking about it and decided to try a washer. We had trouble years ago with the Hatori headers coming loose and this was when the washers were too compressed inside the exhaust port of the motor. A new washer made it stay tight. We tried the washer deal and VIOLA it stays tight.

What happens is the copper is soft and will compress. Since it compresses a little then when it heats up it stays tight.

Another trick is to run the motor and get it hot. Then go in and tighten the header up when the motor is still hot. I actually use a socket wrench to tighten it and they don't come loose. I have never seen a stubborn one come loose after it was tightened HOT.

The real key is the copper washers. Once you use them you don't need any silicone sealer or anything.

YOU do not want to use the setscrew idea. What happens is it will loosen a little then the bushing nut will auger out the aluminum body of the header and ruin it. Just cut off the set screw you have so it acts to plug the hole you have in the header now. Sitck some silicone on the screw and tighten it up. You don’t want that set screw touching the bushing….It can cause problems when it heats and cools. As thing expand and contract damage can be done to the header. I tried this idea early on last year 2004 and it was good thought but didn’t work well.

Let me know if you have any more trouble…..If you need some more washers central has them. They are a perfect fit. I will see if I can dig up some extra too. I think I have a handful of them around here somewhere.

Troy