These valves were later eliminated from some models but the side cover is still there, but it’s just blank. This helps prevent that lean backfire that occurs on some motorcycles when you suddenly let off of the gas. The purpose of this valve is to temporarily restrict the flow of air through idle air circuit when the throttle is suddenly snapped shut. Of course if you doing this for an off road, race only machine 😉 you can carefully grind the tab off before re-assembly.Īnother big difference on some machines is the presence of an air cut off valve often found under a cover like this. The float bowl must be removed first to remove these screws. This is one thing that is found on the early emission controlled Hondas (late 70s & early 80s) is this pilot mixture screw with the tab on it to prevent it from being rotated too far in on direction or another.
Some machines (but not this one) may even have different jetting between different cylinders so just play it safe and don’t mix your parts.Īt this point instead of a big complicated looking rack of carbs, you are now just rebuilding 4 individual carbs with only a few differences from you average Always keep the parts from each individual carburetor together, never mix them up because there are some small differences in every set even if it’s just wear patterns. Here is a shot of all the major components laid out on the bench more or less in order. Carefully drive out this rolled pin to remove the return spring and remove the shaft completely from all the carbs.
On this motorcycle the throttle return spring is fitted between this bracket and the number three carburetor. Here’s a shot of the two middle carbs with the vent hoses in the foreground and everything else behind them. In fact if you have never done this before I suggest taking a copious amount of pictures at each stage of dis-assembly to help you remember if the doohickey is pointed toward the watcha-ma-callit or the thinga-ma-bob. Lay everything out on your workbench in the order that it comes apart with everything facing the direction that it goes back together correctly. Then you can slide the two outer carburetors off the shafts and lay them out along with all of the parts that go between each carb. On this set there is one large bracket on the engine side & two small braces on the air cleaner side. Once you have everything loosened or removed from the shafts it’s time to remove the brackets that hold the rack together. use a strip of sand paper or emery cloth to remove anything you find like this prior to dis-assembly. At some point a previous owner had used a pair of pliers to move a sticky slide. pliers marks, I hate pliers marksīe sure to inspect the shafts for damage like this before you start pulling the unit apart. Next take the tops off and remove the long screws that connect the slide lifters to the throttle shaft. This often makes them a pain in the butt to remove. Please note that these screws are often punched from the backside at the factory to spread them out & keep them from coming loose & falling into a running engine. What the heck is a JIS screwdriver you ask? Just click here to find out! Here I am using a JIS screwdriver to remove the choke butterflies. The first step in getting a set of carburetors apart is to remove everything you can from the choke & throttle shafts. This is not rocket science but there are no shortcuts either. Please note that successful does not mean easier.
1980 HONDA MOTORCYCLE HOW TO
Instead I will focus on how to disassemble the set of carbs, and point out some of the different features along the way, along with a few tips and tricks to make the job more successful.
If need to learn the basics of carburetor repair I suggest that you start by clicking here. This will not be a complete step by step guide to restoring every single piece. Although these a very similar to the piston valve or round slide carbs used on a number vintage motorcycles these do have a few differences from the older ones. The patient is my own 1980 Honda CB650 Custom with a set of Keihin PD mechanically operated carburetors. This is not everything you need to completely disassemble them but it’s a good start. Here you see the four carburetors, along with a flathead screwdriver, a JIS screwdriver, a set of mini wrenches and a ratchet with a socket.
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