Re: 82 CB750C smoking and missing a little. Need help plz.
Posted by GreenSkullCB750C on Jan 11, 2019; 1:14am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/82-CB750C-smoking-and-missing-a-little-Need-help-plz-tp4063611p4063900.html
Hey guys back with that update I promised. So this has been a journey for me but I learned a great deal about the bike and what essentially was happening. Starting off I want to first and foremost exaggerate the fact that these things called "SPECS" actually mean something when it comes to certain models. Okay with that out of the way let's begin. I had a nasty little "DUO" of problems going on. First thing was not the Ignition Coils like I first presumed. No, It just so happen be this little thing called the "Air Cut-off Valve". Basically this operates with a rubber diaphragm located on the left side of each carburetor. When the throttle is open i.e. demanding more air the diaphragm due to the vortex of pressure change, closes so when cruising or gettin on it, it's closed allowing more fuel trim from the jets. Now when you close the throttle i.e. slowing down, the closing of the throttle butterfly changes pressure therefore opening certain fuel passages that allow the cylinder to keep getting fuel while the butterfly is closed. This "Air Cut-off Valve" being bad was making the cylinder basically run dry through the cycle of combustion. Now on to the Second part of this fiasco. The second problem I encountered was I absolutely had the wrong type of Spark Plugs!!! This was the icing that topped the cake and let me explain why. At first glance when the problems all started, I went off what kind of plugs the previous owner had had in the motor. Total mistake on my part! the plugs he had were platinum or iridium center electrodes. When I bought new ones the first time they were still wrong smh. Finally I discovered that there are Canadian models of CB that require a specific plug I guess for a certain reasons I'm unaware of BUT, My model calls for a copper center electrode spark plug. So with the number 4 carburetors "Air Cut-off Vlave" blown the cylinder wasn't getting any fuel but the other 3 were! Then the spark due to the wrong material the spark plug had, caused weak firing of the spark and it was erratic not consistent which in turn was also creating a misfire. So 1 misfire caused by 2 seperate problems! Now she purrs like a kitten but growls like a tiger! Hope this helps! Cheers
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/82-CB750C-smoking-and-missing-a-little-Need-help-plz-tp4063611p4063900.html
Hey guys back with that update I promised. So this has been a journey for me but I learned a great deal about the bike and what essentially was happening. Starting off I want to first and foremost exaggerate the fact that these things called "SPECS" actually mean something when it comes to certain models. Okay with that out of the way let's begin. I had a nasty little "DUO" of problems going on. First thing was not the Ignition Coils like I first presumed. No, It just so happen be this little thing called the "Air Cut-off Valve". Basically this operates with a rubber diaphragm located on the left side of each carburetor. When the throttle is open i.e. demanding more air the diaphragm due to the vortex of pressure change, closes so when cruising or gettin on it, it's closed allowing more fuel trim from the jets. Now when you close the throttle i.e. slowing down, the closing of the throttle butterfly changes pressure therefore opening certain fuel passages that allow the cylinder to keep getting fuel while the butterfly is closed. This "Air Cut-off Valve" being bad was making the cylinder basically run dry through the cycle of combustion. Now on to the Second part of this fiasco. The second problem I encountered was I absolutely had the wrong type of Spark Plugs!!! This was the icing that topped the cake and let me explain why. At first glance when the problems all started, I went off what kind of plugs the previous owner had had in the motor. Total mistake on my part! the plugs he had were platinum or iridium center electrodes. When I bought new ones the first time they were still wrong smh. Finally I discovered that there are Canadian models of CB that require a specific plug I guess for a certain reasons I'm unaware of BUT, My model calls for a copper center electrode spark plug. So with the number 4 carburetors "Air Cut-off Vlave" blown the cylinder wasn't getting any fuel but the other 3 were! Then the spark due to the wrong material the spark plug had, caused weak firing of the spark and it was erratic not consistent which in turn was also creating a misfire. So 1 misfire caused by 2 seperate problems! Now she purrs like a kitten but growls like a tiger! Hope this helps! Cheers
| Free forum by Nabble | Disable Popup Ads | Edit this page |