I’m not trying to debate the merits of the SK meter over a 4-way manometer or vice-versa, but I did notice something odd that can cause false readings on cylinder 4. And since that’s the most critical reading, because you’re setting the other three carbs to match, it can cause you a headache.
In case you’re not familiar with the SK airflow meter, it has a rubber end that you stick into the carb venturi, a plastic body perforated with vents, and a sliding-scale meter in the middle. The carb draws air through, airflow disturbs the needle on the meter, which reads the value and you know how many kilograms/h of air are moving through. You then set the other 3 carbs to the same reading.
However, In the bottom of the air filter housing “box” is the crank case breather port. It bisects a tab of plastic that sticks straight up inside the perimeter of the air filter, presumably to keep blow-by oil from soaking the air filter so bad. Anyhow, If you have the lower lid still attached, or even if you have the lower portion removed and the crank case breather tube is just pointing up, that tube may be pointing directly at the back of the airflow meter when it’s connected to carb number four. And if the puffs of air from that breather tube blow across the meters intake vents, it can be enough to affect the meter.
In my case the meter read one full point higher when disturbed, and that reading dropped back down when I cupped my hand behind the intake vents (without blocking them in any way, of course) or when I stuffed a shop rag over the crankcase port.
I still think using the SK airflow meter can be a perfectly acceptable way to synchronize the carbs, this is just a ST1100 quirk to keep in mind when doing the job to protect yourself from false readings. Cheers!
In case you’re not familiar with the SK airflow meter, it has a rubber end that you stick into the carb venturi, a plastic body perforated with vents, and a sliding-scale meter in the middle. The carb draws air through, airflow disturbs the needle on the meter, which reads the value and you know how many kilograms/h of air are moving through. You then set the other 3 carbs to the same reading.
However, In the bottom of the air filter housing “box” is the crank case breather port. It bisects a tab of plastic that sticks straight up inside the perimeter of the air filter, presumably to keep blow-by oil from soaking the air filter so bad. Anyhow, If you have the lower lid still attached, or even if you have the lower portion removed and the crank case breather tube is just pointing up, that tube may be pointing directly at the back of the airflow meter when it’s connected to carb number four. And if the puffs of air from that breather tube blow across the meters intake vents, it can be enough to affect the meter.
In my case the meter read one full point higher when disturbed, and that reading dropped back down when I cupped my hand behind the intake vents (without blocking them in any way, of course) or when I stuffed a shop rag over the crankcase port.
I still think using the SK airflow meter can be a perfectly acceptable way to synchronize the carbs, this is just a ST1100 quirk to keep in mind when doing the job to protect yourself from false readings. Cheers!
