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Discussion Starter · #1 ·
A few weeks ago I rode to work as I usually do, nothing notable on the way in. On my way home it was running without a single issue until I got caught in some traffic. After a mile of stop and go I noticed the throttle response was terrible and looked down to see a decent amount of fuel pouring from the carb 3 and 4 overflow tube and pulled over. (This has happened twice before and a gentle tap with the handle of a screwdriver on carbs 3 and 4 fixed it, this time it didn't). It idled fine, but once the throttle was cracked open there was no power.

I decided to try and ride the shoulder home, it took about 10 seconds riding the clutch to get it up to 25, and after 1/4 throttle in second gear it acted as if nothing was wrong. I was able to get it home, did some research and found the first thing to do is clean the carbs. So I pulled them off, removed the float bowls, and found the o- rings and gaskets dry rotted. I ordered all new o- rings and gaskets and disassembled the carbs while I waited for them. I soaked all the brass in B12, recorded the pilot needle settings (they were all between 1 and 4 turns out), used a size 9 guitar string to clean the jets (no scraping, just removing deposits) and hand cleaned everything else with pine sol and a nylon brush.

I put everything back together, bench synced the carbs and put them back on the bike. I should also mention this is my first time dealing with motorcycle carbs. I found some tuning instructions, started the bike, and now it won't run on cylinder 3. There's no vacuum leaks.

I checked the pilot screw settings (first to the recorded settings, then to the manual at 1-1/2), no difference). Performed a compression test, every cylinder is running at 70psi, so I thought maybe the timing chain slipped a tooth and isn't allowing the valves to be at their proper locations during each stroke, so I pulled the valve cover and pickup cover and checked the timing, all good (13 pins between both cam marks, correct mark at the pickup coil, looks just like the picture). I check the cam chain tensioner, it was seated fine and installed as directed. I am able to get cylinders 1, 2, and 4 running and balanced, but I can't figure out what's going on.

It won't rev above 4k (typical of running a cylinder down) and taking it for a ride proves it.

Some additional info, everything is stock except the muffler which has no baffle in it (it rode 5,000 like that from the previous owner before I put another 14,000 on it). There's about 41,500 miles on it, oil and filter + plugs are changed every 4,000. I regularly clean the air filter and notice no difference with or without it. It ran unremarkably similar for the 14,000 miles I put on it with no noticeable change in performance or fuel economy. The valve clearances are all within spec.

Any help would be appreciated.
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