idle drop procedure
Posted: Tue Mar 13, 2012 11:57 pm
i havent seen this posted anywhere or heard any mention of it in any posts, so i thought id share it with you all. its an easy way to tune your bike without a thermometer, tailpipe sniffer, or O2 sensor. all you need is a screwdriver and either a tach or a good ear. they taught us this trick at mmi, and i used it to pass emissions today. its a handy skill to have, as long as you know how to listen to what your engine is trying to tell you.
1.first thing to do is make sure your bike is running well mechanically. good compression, good valves, clean carbs, carbs synchronized, etc etc. also it needs to be warmed and up to normal operating temperature. right around 200 to 215 degrees. make sure you use a fan to keep the engine from overheating.
2.next set your idle to the factory specs, around 1200 to 1400 rpm
3.now you will want to set all your screws to the factory setting, usually around 1.5 turns out. however i know these bikes were horribly lean from the factory, so i started at 2 turns for each carb.
4.now you go to the first carburetor (i went left to right, port to starboard, etc) and turn the pilot screw out a half turn at a time until you hear the idle hit its peak rpm. after about 4 or five full turns it will usually drop. after you have turned the pilot screw out til the idle drops, turn it in until the rpms peak(it should plateau for about one full turn) and reset your idle rpm. its probably best to do this to each carburetor before moving on to step 5. i didnt, but its a good idea. make sure your idle doesnt go over 1500 rpms, as your carbs will start drawing fuel from other circuits and throw all your settings off.
5.now if you are like me and need to pass emissions turn the pilot screw in a quarter turn at a time until the idle drops 50 to 100 rpm. when it does, back the screw out a half turn, and this will be its final setting. if you dont need to pass emissions and want to run a little richer setting (more power, cooler running at idle), turn the screw out until the idle drops 100 rpm, then turn it back in one half turn. repeat this process with all four carbs, and if its been done right your bike should be running great.
if you have very little experience tuning engines you may want to practice on a little single cylinder or a twin cylinder. this is actually a very accurate method of tuning your idle circuit, and i was taught by the pros at mmi. we used it on all the bikes at school.
this method works on all types of carbureted motorcycles, however, its much easier to do on a twin or a single because you can hear the idle drop much more easily. we called this the honda idle drop procedure at school, because only honda teaches it. other people may know it by a different name.
have fun!
1.first thing to do is make sure your bike is running well mechanically. good compression, good valves, clean carbs, carbs synchronized, etc etc. also it needs to be warmed and up to normal operating temperature. right around 200 to 215 degrees. make sure you use a fan to keep the engine from overheating.
2.next set your idle to the factory specs, around 1200 to 1400 rpm
3.now you will want to set all your screws to the factory setting, usually around 1.5 turns out. however i know these bikes were horribly lean from the factory, so i started at 2 turns for each carb.
4.now you go to the first carburetor (i went left to right, port to starboard, etc) and turn the pilot screw out a half turn at a time until you hear the idle hit its peak rpm. after about 4 or five full turns it will usually drop. after you have turned the pilot screw out til the idle drops, turn it in until the rpms peak(it should plateau for about one full turn) and reset your idle rpm. its probably best to do this to each carburetor before moving on to step 5. i didnt, but its a good idea. make sure your idle doesnt go over 1500 rpms, as your carbs will start drawing fuel from other circuits and throw all your settings off.
5.now if you are like me and need to pass emissions turn the pilot screw in a quarter turn at a time until the idle drops 50 to 100 rpm. when it does, back the screw out a half turn, and this will be its final setting. if you dont need to pass emissions and want to run a little richer setting (more power, cooler running at idle), turn the screw out until the idle drops 100 rpm, then turn it back in one half turn. repeat this process with all four carbs, and if its been done right your bike should be running great.
if you have very little experience tuning engines you may want to practice on a little single cylinder or a twin cylinder. this is actually a very accurate method of tuning your idle circuit, and i was taught by the pros at mmi. we used it on all the bikes at school.
this method works on all types of carbureted motorcycles, however, its much easier to do on a twin or a single because you can hear the idle drop much more easily. we called this the honda idle drop procedure at school, because only honda teaches it. other people may know it by a different name.
have fun!