September 2024

On the seventh of the month, a pleasant late-summer Saturday, I set out on the bike to meet some NER friends in New Hampshire. The destination was a newly discovered BBQ joint, in keeping with my string of summertime rides-to-eat. After only a few miles riding up I-495, I began to notice a knocking vibration in the ST1300’s operation, coming up through the foot pegs. Uh-oh, what now? I’d thought I’d noticed something being slightly off towards the end of the RACT attempt, but had written it off as just being tired and fussy by the end of that long day.

Exiting in Hopkinton, I pulled into the empty parking lot of a nearby business park to try to listen and isolate the noise I was hearing. Looked at the tires and wheels and saw nothing obvious. Unfortunately, the problem wasn’t noticeable with the bike running in neutral. Maybe I was imagining things after all? But no, as I began riding back to the highway, it was definitely there. Reaching the interstate, instead of continuing north I turned back south towards home – my hopes of BBQ and camaraderie dashed for the day.

My thoughts are whirling, trying to diagnose what this might be. The sound and vibration seemed to increase in frequency in relation to ground speed, but not directly with the turn of the wheels. Also seemed to be independent of the throttle input. Have I checked the oil level recently? I think I changed it after the LDX rally (?), but I don’t generally look at the oil level before every local ride. I really hoped that I hadn’t overlooked it and done damage to the engine.

Even though I’m only 15 minutes from home, I pull up a list of AutoZone locations on my phone and exit in Milford to grab some Mobil 1 to top things off. I was actually able to pour in 1.5 quarts of oil, which further fed my belief that my engine might have some damage. The vibration didn’t ease up, so I ended up leaving the interstate entirely to use local roads to get home at a more sedate pace, in hopes of minimizing any further damage to whatever.

Back at home, I had Char take some video (with sound) of me riding up and down our street so I could try to verify the sound from an off-bike perspective. She heard the sound and once I watched the video, I knew I wasn’t crazy (for this reason anyway). I got the bike on center stand up on a 2×6 and was able to replicate the problem with the rear wheel off-ground and running in first gear. It definitely seemed to be coming from the right side, lower down. Now my thoughts were leaning more to a driveshaft or u-joint issue. I immediately sent the videos out to my mechanic friends to get some opinions. Survey says: u-joint almost definitely. *sad trombone*

I immediately looked up the process to service the u-joint in the manual and online, then ordered the necessary parts right away. There’s a special single-purposed Honda tool required for this task as well, to get the retaining lock-nuts removed from the main swingarm pivot bolts. It’s pricey at $140, but there is no other surefire solution presenting itself. I didn’t feel like trying to cut notches in a socket or any of the other home-brew suggestions I found on the ST forum. Do what you gotta do to keep the bike on the road, right? I need to be sure and get the bike running in time for an upcoming trip in October.

I spent more time over the next few days re-reading several articles on the st-owners.com forums and learning a bit more about the ST final drive layout. I used the time to get the bike cowls and rear wheel removed, and the garage prepped for invasive surgery. Miraculously, the parts and tool arrived late week, so I was tearing into the rear drivetrain by the following Saturday morning.

 

The connection between the drive components itself is pretty straight forward: the joint simply slides on to the splined ends of the two shafts, allowing transfer of power. But this is one of those jobs that seems to require having three hands.

Getting access to the area where the u-joint connects the driveshaft to the engine shaft is not an easy business on the Honda ST. As usual with anything major on this bike, you have to remove the seat and most of the plastic cowling. Then the mufflers, and the rear wheel of course. Then you have to really dig past the evap canister and miscellaneous frame braces and heat shields all bolted to the right side of the bike, so you can get to where the swingarm case joins the main frame. The entire rear drive “pumpkin” then has to be removed from the swingarm, including the driveshaft, which slid pretty easily out of the u-joint, leaving it hanging off the engine shaft.

There’s not enough room to remove and reattach the u-joint with the hollow aluminum swingarm in place. You must partially detach it and sort of leave it hanging in limbo (to avoid the complexity of removing other attached sensor components). Then insert the driveshaft back through the swingarm, leaving enough space to get your hands in to get the new u-joint to slide onto both splined shaft ends. To top it off, the u-joint itself must be protected by a bulbous rubber boot, which needs to be stretched over the rim of the openings to form a dirt-proof seal.

After getting the u-joint out, even I could tell that it was seriously f’d up by waggling it around and seeing it wobble and stick through what should be a smooth-as-butter operation. The amount of metal shavings retrieved from inside the swingarm with a long magnet was a pretty good clue as well.

The articles from the st-owners.com forum were a huge help (as usual) in understanding what I was in for and eliminating a lot of the unknowns ahead of time. The tips there helped me feel confident I was approaching the job in the least problematic fashion. Getting the rubber boot properly seated (I hope!) around the joint was the fiddliest and most time-consuming part of the actual replacement process, resulting in some bloody knuckles and frequent cussing.

It was one of the longest hardest days of wrenching I’ve done on the bike to-date, but I had the whole drive assembly back together by evening. Enough to run the bike in gear on the center stand and confirm – no more clunking sound! Exhausted from crawling around the entire day on my knees, I took the win and called it a night. I followed up the next day by reassembling the bike completely and riding around the block – so far so good! That was about all I had energy for, so I followed up the next day with one of my standard hour-long back-road rides. Yes, it’s fixed! 🎉

Big shoutout to my mechanically-inclined friends (Jim & Jeff) for their informational and moral support… thanks guys!