A sinner in the Church of Clean...

Making this post as a penance, and as a warning to all others who may trod down my forsaken path. I have sinned against the church of clean, and it cost me many months of headache. A long post is coming.

Flash back to this past winter, when I needed to do a lot of work on my XJ650 that had sat unused for decades. One of my carbs had a broken float post, so I ordered a replacement carb body from chacal. I had already performed a carb rebuild when I got the bike, since the pipes connecting the carbs were leaking fuel. And yet, I never replaced the throttle shaft seals. Why didn't I? To be honest, I was intimidated. This is my first bike, and I've never even done car maintenance more difficult than changing a flat. The bike seemed to run fine, but now that I needed to completely tear down carb #2, I figured I might as well swap out those throttle shaft seals too.

I get carb #2 apart, and lo, the throttle shaft seals seemed okay. They were still soft and pliable. I replaced them, since I had the parts on hand. But a new thought entered my head. The other carbs... are probably okay, right? Do I really need to change the seals on those too?



Well, fast forward to now. Ever since I put everything back together and synched the carbs, I have been having misfires on cylinder #2. It seemed strange to me. That's the one I replaced the throttle shaft seals on, so why should it be the one giving me trouble? I had troubleshooted the ignition circuit, wondering if maybe there was something wrong with the spark system. I made a few posts over in the technical chat, trying to figure out what was wrong. Everything checked out okay.

Finally I decided to bite the bullet and take the carbs off the bike again. There had to be something wrong with the fueling from the carburetors. Open them up, and what do I see? Butterflies #1, #3, and #4 are all open by about the same amount. But butterfly #2 is nearly closed.

Oh no.

Suddenly, everything made sense. There was a vacuum leak in all cylinders but one. Thinking back, my starter circuit had always been weak. It started the bike just fine, but it would never rev quite as high as it's supposed to on full choke. Almost as though it wasn't capable of enriching the mixture enough.

Humble pie finally eaten, I bit the bullet and replaced the throttle shaft seals on all carburetors. Turns out it's actually pretty easy, if you don't mind taking the rack apart. Here's a pic I snapped of the old seals. Pretty crusty, no?



Put the bike back together, and it runs great. Was easy to synch, and I have even firing on all cylinders. Seems my penance is complete. I think I learned my lesson too. There are a bunch of experienced folks on this forum (chacal, hogfiddles, k-moe, etc.) who preach how taking shortcuts will lead to more work in the long run. You might think you know better. Well, you don't. Or at least, I certainly don't. I suppose this is just another example showing why the right way is the best way.

Anyways, thanks for coming to my TED talk. Nice to having a running XJ again.