It’s been a while since the NC23 figured in the list of projects. It hasn’t been ridden much over the past half a year, because it would leak gas from somewhere around the carburetors, and I was busy with the NC30 project. However, finally the state of Hawaii ensured the NC23 got some love, since it was time to get its annual safety inspection.

After removing the fairings and the airbox, it appeared the gas was coming from the pilot screw on the #1 carb (although it was hard to tell since they were so dirty…) Upon removal, the tiny O-ring that seals the pilot screw was found to be in sad shape. The O-rings for the float bowls were also hard and crusted with varnish. Since I had them out of the bike anyway, I figured it was time for a carb overhaul.

There are still O-ring kits for these carbs available from Honda. One set (16010-MN4-305, $20 each) has the internal O-rings, and another set (16040-MM5-601, $11 each) has the O-rings for the pipes that connects the fuel supply and vent lines between the carbs. According to the parts list, you need 4 of the former and 6 of the latter, making this a $140 project from O-rings alone…

Unfortunately I didn’t discover that there was a second set until I got the first one, so that meant waiting another week-ish for the second. Then I discovered that the second kit doesn’t actually contain all the O-rings the parts manual says it should, so I still didn’t have all the parts needed. Quite frustrating, to say the least.

At this point I found a company called LiteTek in Thailand that seems to specialize in manufacturing O-rings for motorcycles. They had a kit for the NC23, comprising both the Honda kits and the missing O-rings and new rubber caps for the choke plungers which Honda doesn’t have at all. Their O-rings are also made from Viton, rather than butyl rubber like the factory ones, and Viton stands up to fuel with ethanol in it much better than butyl rubber. On top of that, their kit was $37, including shipping. What a no-brainer!

While waiting for the parts, I had been cleaning everything out. I remember from cleaning the NC30 carbs how hard it was to get all the varnish off, so this time I looked a bit harder for a solution. Quite a few people on the web reported much luck with Berryman’s Chem-Dip, and luckily the local auto parts store had a can of it. (Chemicals like these cleaners aren’t something Amazon wants to ship over here, so your best bet is to find something locally.)

This stuff is amazing! After stripping off all the parts I could, I soaked the carbs in the cleaner for an hour or so. Check this out:

This is a before-and-after image of how the carbs came out after spending an hour in the Chem-Dip can. Amazing!

Similarly, the various jets and needles that were crusted with stuff came out looking if not quite like new, much, much better than before.

Here are the needle jets and the pilot screws before and after cleaning.

Once I got the set of Thai O-rings (they arrived faster than many mainland USPS shipments) it was assembly time. The O-rings looked good. I had already broken the packaging on the set of internal O-rings, but I took those out and replaced them with the Viton ones in the interest of longevity.

A selected set of carb O-rings. The green ones are the Viton seals from LiteTek, the black are the factory ones. (There should be no question which ones are the old ones.)

Compared to the long wait for parts and all the cleaning, the actual assembly just took an afternoon.

The assembled set of cleaned and overhauled carbs.

Here I ran into the first setback: when I hooked them up to the fuel supply, they leaked! There was gas seeping from the float bowls on all 4 of them. Clearly the Thai O-rings had some issues. Just to make sure it was the O-rings, I replaced one of them with the factory one. This did not leak.

After contacting LiteTek, they investigated and admitted that there was a manufacturing defect with the float bowl O-rings for these carbs. They refunded me and promised to send me a new set. It was nice that they owned up to the problem so quickly. However, I didn’t want to wait an unspecified time for them to manufacture a new batch, so I decided to go ahead and use the factory O-rings for the float bowls since I couldn’t return those anyway. I filled the carbs with gas and left them overnight just to be sure. No leaks.

Once I re-mounted the carbs, added fresh grease to the throttle and choke cables, and cursed the appropriate number of times about getting the carbs back on the rubber mounts and hooking up all the hoses, it basically started right up. Once I checked that it was running OK, I headed for the now-overdue safety inspection. Mission accomplished!

Now the only question is how I’m going to get the NC30 inspected…