So yesterday I finally got at the 79’ with the BS38’s because I’ve been tied up working on an 81’ lately. I ordered some new pilot mix screws and needle jet o-rings ahead of time from mikesxs.
So my issue has been the right side carb like I stated earlier. I pulled the carbs, drained them, and started pulling them apart. Before I took them apart, I tested the slide diaphragm and choke by raising the slide and plugging the hole and both slides dropped very slowly. When I let my finger off the hole they both drop fast. I flipped the carbs over and removed the float bowls and everything looked normal. I tried to remove the float bowl gaskets to measure float height and destroyed one of the gaskets so I ordered some new ones. The floats measured out within spec. I then removed the floats and pulled the float needles and set them aside.
At this time, with the carbs upside down, I pushed in the slides just to see if they would return to the idle position with the springs upside down. The left side slide made it back to the idle position, the right side slide (the side that’s having the issue) seemed to get hung up and wouldn’t return to the idle position unless I helped it a little. Not sure if this would cause the right side to run richer but it was something to note as I disassembled the carbs further.
Next I pulled out the pilot mix screws. Everything, as far as the tips of the screws go, looked normal as far as I could tell. Both mix screw springs were present. The o-ring on the left side mix screw (the side not having any issues) was broken/torn-through so I’ll be replacing that. With the choke seeming to be working from the slide drop test and the mix screws looking good, I’m still not understanding what would cause me to be able to completely close the right side pilot mix screw and still have the bike be able to idle on only the right side cylinder by itself.
Then I pulled the carb tops and removed the slides from the carb bodies. I checked the diaphragms against a bright light and didn’t see any holes. The one thing I did notice is that the right side diaphragm seemed thinner than the left side. More floppy I would call it I guess. But with the costs of new slides and diaphragms and the fact that the diaphragms I have seem to not be leaking, I’m just going to reuse them.
Getting back to the right side slide sticking issue that I mentioned earlier, I examined the slide and the carb body to see if the slide would be hanging up on any gunk or anything and didn’t notice anything. I reinstalled the slides and just tested them by pushing them through the carb bodies by hand and they both seemed to slide through easily with neither getting hung up on anything. I will clean the slides and carb bodies with some solvent and a rag though before I reassemble to make sure they’re clean. As for the springs, they’re the same size and both seem to have around the same pushing force when I squeeze them together. Not sure how else to tell if a weak spring is causing the “sticking” issue I mentioned before. I did look at getting new springs but wasn’t able to find any for the 78-79 bs38’s.
Next I pulled the needle jets, or tried to. I know it was mentioned that the o-rings could be bad and causing my right side symptoms but they seemed to be in place pretty solid. In fact, they were completely seized in and I wasn’t able to push them out by hand, even with the little bit of liquid wrench applied. I ended up having to resort to a needle nose pliers to kind of break them free. They got marred a little bit on the rim of the jet but not bad and nothing I did distorted any of the portion of the jets where the actual holes are so they should be fine. Once I broke them free I was able to work them out. Both o-rings were intact and seemed to be fine but I’ll be replacing them with the ones I ordered from
Mikes.
So that’s as far as I got so far. Any thoughts on anything that I mentioned? I’m still not understanding my right side mix screw situation and why it doesn’t completely shut off the idle when completely leaned out (all the way in) like the left side does. And I’m still not understanding what might be causing the right side to run a little rough and more rich than the left at this point.