jcorney
77 XS400
So I am close to being complete with my restoration on my '77. I have rebuilt the motor and fitted tin top carbs from a newer model on it. It is running, but I have been having issues with the idle. Initially when I got it started it idled normally, but after it warmed up a bit, the rpms climbed to 4000 and hung there. I decided to check the carb diaphragms and found that one of them had a couple of small cracks in the lip that fits into the carb body. As a temp fix, I put some silicone in the groove that the diaphragm fits in. It seemed to help temporarily, and it idled at 1500 rpm. However now it has a light backfire (mostly on the right side) which is kind of a crackle. It also has a intermittent knock. It is by no means consistent. So my questions are what could the knock be, and if I have "tin top" carbs, what is the dimension of slides? I want to buy new diaphragms from JBM Industries, and I want to make sure I order the correct size. Any help would be appreciated. 
