Cleaning carburettors
Posted: 28 May 2018, 01:15
As a constant recurring theme is blocked up carburetors thought it worth sticking down a few thoughts on the subject.
On infrequently used bikes, or bikes that will not be used for a period of time, the carburetors should be drained before putting the bike away. It is the fuel evaporating out of the bowls as the engine sits idle that is the main cause of the problem. The fuel evaporates away leaving behind residues which set rock hard. This buildup continues each time till it completely blocks fine jets, sticks float valves etc. Ways to drain the carbies ....
1. Open the drain screws in the bottom of the four float bowls to drain them,
2. Disconnect the vacuum pipe at the back of the fuel tap and let the engine idle till it stops from running out of fuel (remember to turn off the ignition switch)
3. Fit a manual fuel tap, turn it to off, and let the engine idle till it stops.
Draining the carbies won't 100% eliminate the problem, but it will extend the interval between potential problems by a massive amount.
Cleaning carby jets. This buildup sets so hard that there is no guarantee that chemical or ultra sonic cleaners will remove it from inside the jets. Mechanical removal is the only sure way. That is easily done with main jets as they are large enough to run a piece of fine nylon fishing line through to scrape this crap off the internal walls of the jet. But the #35 pilot jets are so small that even the smallest diameter fishing line is near impossible to thread through. Just because you can see light through the jet if held up to the sun is no guarantee there is not buildup on the walls making the jet effectively a smaller size. So really replacement with new genuine Keihin pilot jets, easily obtained at about $5 each is the best solution.
On infrequently used bikes, or bikes that will not be used for a period of time, the carburetors should be drained before putting the bike away. It is the fuel evaporating out of the bowls as the engine sits idle that is the main cause of the problem. The fuel evaporates away leaving behind residues which set rock hard. This buildup continues each time till it completely blocks fine jets, sticks float valves etc. Ways to drain the carbies ....
1. Open the drain screws in the bottom of the four float bowls to drain them,
2. Disconnect the vacuum pipe at the back of the fuel tap and let the engine idle till it stops from running out of fuel (remember to turn off the ignition switch)
3. Fit a manual fuel tap, turn it to off, and let the engine idle till it stops.
Draining the carbies won't 100% eliminate the problem, but it will extend the interval between potential problems by a massive amount.
Cleaning carby jets. This buildup sets so hard that there is no guarantee that chemical or ultra sonic cleaners will remove it from inside the jets. Mechanical removal is the only sure way. That is easily done with main jets as they are large enough to run a piece of fine nylon fishing line through to scrape this crap off the internal walls of the jet. But the #35 pilot jets are so small that even the smallest diameter fishing line is near impossible to thread through. Just because you can see light through the jet if held up to the sun is no guarantee there is not buildup on the walls making the jet effectively a smaller size. So really replacement with new genuine Keihin pilot jets, easily obtained at about $5 each is the best solution.