Due to minor repairs needed from a wreck a couple years ago (bent handlebars, broken off mirror, cracked throttle grip, snapped tibia, etc.) my 1984 Honda Shadow didn’t get ridden much recently (as in a handful of times in 2 years). Now that weather is good and most things have been repaired, I went to pull the bike out and to my dismay, I could only get it to idle and only so with the choke on. Every time I tried to rev it at all, it would die even after letting it warm up for a while. After a few seconds of deep thought, I realized that one or both jets must be clogged and I initially dreaded having to clean these since as far as I know they have never been off the bike and there are two carbs crammed in between the cylinders. After taking a good look, I realized it shouldn’t be too bad in taking those off and giving them a much needed cleaning. Whether you have an 50cc motorcycle or a 1600cc v-twin, the general principle for cleaning a carb is the same and in most cases (not all), plugged jets or passages are what cause a motor not to run if it’s been sitting awhile and ran fine previously.
I won’t go through the fine details of removing my carbs from this bike in particular but my goal is to show you how to clean a carb quickly and efficiently to get your machine running again. In my case I had a good idea that the pilot/secondary/slow jets were plugged hence any attempt past a choke enriched idle resulted in fuel starvation. In my case even barely twisting the throttle would kill it. Enough rambling, let’s get it taken apart and cleaned!
You’ll want a clean work space where you can put your carburetor and small parts once you get it off the machine. I used a piece of particle board that I had laying around and put a couple shop towels on it.
Start by removing anything in the way of taking off the carbs. In this case I had to remove the gas tank (which required removing the seat) and air intake (old plastic ones like mine can be brittle so work in warm weather and be gentle). From there I unbolted the throttle linkage from the side of the carburetors and then loosened all the carburetor boots (both inlet and outlet of the carburetors). There was also a choke cable actuated plunger that screwed into the side of each carburetor that I removed and left hanging.
Once you have the carburetor(s) removed, take them to a clean work space and remember that the float bowls will probably be full of gasoline so make sure to drain them (some have drain screw on bottom of float bowl or you can just gently tip them back and forth and upside down until all
the fuel comes out) out so you don’t have a puddle on your bench when you start opening them up.
First things first, take off the float bowl so you can access the float, float
valve, and jets. This is usually secured with 4
screws. If yours has a rubber gasket like mine, you might get lucky and get away with reusing it but gaskets are cheap, so it’s always a good idea to replace it anyways.
Once you have the carb bowl off, remove the jets with a wrench or screw driver. If you do more than one carburetor, keep the
jets separate so you know which carb they go to as sometimes there will be different sized jets on one carb (my main jets were different sizes). As you can see from the pictures, my main jet was clear as I suspected but my pilot jet was completely plugged up on both carburetors. To remedy this, I used a piece of copper wire from some stranded 10 gauge automotive wire and carefully twisted it into the clogged portion until I got it to go
through. Then I fished it all the way through and worked it back and forth like dental floss. This has worked well for me and is cheap! Makes sure all the side holes in the jet tubes are clear as well. For good measure, I took all the jets from both carburetors and boiled them in a pan (wife was not home at the time) for a couple minutes to make sure any varnish got cleaned out then dried them out and made sure they all looked good.
While you have the bowls off, look for any other dirty spots like the bottom of the float bowls and clean any gunk out. Mine had some residue in the bottom that probably wouldn’t affect operation but could clog a jet or passage if it came loose or built up more. Also inspect your floats for any cracks or issues (gas inside the floats) and inspect and clean the rubber tip on your float needle valve as well as where it seats. If the valve seat is gunked up or the carb overflows occaisionally, you can use a q-tip and some toothpaste to clean it up. For more on that visit an old blog post of mine about fixing a leaking or over flowing carb.
Depending on what symptoms or how dirty your carb is, you may want to remove the slide needle (aka jet needle) to clean it and inspect the slide and rubber slide diaphragm if you have a vacuum actuated slide. I find that bare minimum, you should spray down the slide with carb cleaner
before assembly since dirt and things typically get stuck on the slide when removing it from the bike. Make sure the diaphragm is not cracked and looks in good shape and check to make sure the slide operates smoothly up and down and that the jet needle is clean. Mine had some varnish build up that was easily cleaned off.
Before assembling the carburetor back together to put back on the bike, I cleaned out the area where the choke plunger goes as it had some dirt or rust buildup that must have got inside the boot and I also sprayed carb cleaner in all the small holes on the carburetor to make sure none were plugged up. After that, put everything back together the same order you took it apart and put it back on the bike! My choke plungers consist of a plastic post that screws into the carburetor so I had to be extra careful not to strip those out. Getting the carbs back onto the boots took some finagling but I finally got them all on. The true test is getting the bike altogether and firing it up for the first time. As I hoped, it started right up after a few cranks and when I started to twist the throttle, it didn’t die! Mission accomplished and my bike is back to it’s normal rev loving self.
I hope this write up helps with your carb issues. Comment below if you have any specific questions. -Matt
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