If you ever sync'ed the carbs on an old Honda we know what a difference it can make in smoothing out a engine. Why doesn't the Honda Service Manual have a procedure how to sync the throttle bodies? I doubt a Honda shop would try it, they would just buy new factory set throttle bodies ($$$).
Anyway, I've been researching it and have an idea on how to do it but would like any advice on how to do it without permanent regrets.
First off, pictures!
This is bottom side of the throttle bodies, cable connection of far left, TPS on the far right. The adjustment on the left will change both throttle plates and the TPS's position. The middle adjustment would only change the throttle plate on the right and the TPS's positon, so it must be what is used to sync the throttle bodies. Honda has painted the 2 adjustments and the TPS and warns not to adjust.
Also shown is the tubing for the MAP Sensor. It senses from both throttle body intake sides and routes to a 3 way tee and then to the MAP sensor. I would think this would be a good place to measure intake vacuum for each cylinder. I got gauges, tubing, splitters & tees. Another possible vacuum sensing points would be the Evap Vacuum hose line that is next to MAP Sensor line. To be honest, I may have labeling the wrong set as MAP sensor, it may be the Evap Vacuum line. It has a similar routing where it goes to each intake and it from a 3 way tee. Here is a pic of the top of throttle bodies that shows the 3 way tees.
So, my general procedure would be:
1. Measure TPS Volts on a idling warm engine at ECU....just in case.
2. Strip NT done to throttle bodies and route capped tubing to exterior for later vacuum gauge use. One cylinder would go a gauge only. The other cylinder would go to a gauge and the MAP Sensor. So now the MAP sensor would only have one cylinder operating it (Good? Bad?).
3. Determine method to reach a wrench/driver to operate middle adjustment screw. Taped or magnetic 1/4" drive with swivels and extension is my first idea. If this isn't possible, this adjustment will consume many days of trial and error.
4. Reassembly NT. Ride and warm up engine.
5. Connect vacuum gauges to each cylinder intake. Pop the throttle a few times to see how synced vacuum is and adjust at idle to match as close as possible.
6. If needed adjust TPS to volts measured in step 1.
Maybe some of the auto & motorcycle mechanics have some experience with this idea. Would I want to cap the Evap Vacuum line while sync'ing? It seems like it would act like an equalizing line between the two intakes if it remains connected.
Anyway, thanks for any help.
Anyway, I've been researching it and have an idea on how to do it but would like any advice on how to do it without permanent regrets.
First off, pictures!
This is bottom side of the throttle bodies, cable connection of far left, TPS on the far right. The adjustment on the left will change both throttle plates and the TPS's position. The middle adjustment would only change the throttle plate on the right and the TPS's positon, so it must be what is used to sync the throttle bodies. Honda has painted the 2 adjustments and the TPS and warns not to adjust.
Also shown is the tubing for the MAP Sensor. It senses from both throttle body intake sides and routes to a 3 way tee and then to the MAP sensor. I would think this would be a good place to measure intake vacuum for each cylinder. I got gauges, tubing, splitters & tees. Another possible vacuum sensing points would be the Evap Vacuum hose line that is next to MAP Sensor line. To be honest, I may have labeling the wrong set as MAP sensor, it may be the Evap Vacuum line. It has a similar routing where it goes to each intake and it from a 3 way tee. Here is a pic of the top of throttle bodies that shows the 3 way tees.
So, my general procedure would be:
1. Measure TPS Volts on a idling warm engine at ECU....just in case.
2. Strip NT done to throttle bodies and route capped tubing to exterior for later vacuum gauge use. One cylinder would go a gauge only. The other cylinder would go to a gauge and the MAP Sensor. So now the MAP sensor would only have one cylinder operating it (Good? Bad?).
3. Determine method to reach a wrench/driver to operate middle adjustment screw. Taped or magnetic 1/4" drive with swivels and extension is my first idea. If this isn't possible, this adjustment will consume many days of trial and error.
4. Reassembly NT. Ride and warm up engine.
5. Connect vacuum gauges to each cylinder intake. Pop the throttle a few times to see how synced vacuum is and adjust at idle to match as close as possible.
6. If needed adjust TPS to volts measured in step 1.
Maybe some of the auto & motorcycle mechanics have some experience with this idea. Would I want to cap the Evap Vacuum line while sync'ing? It seems like it would act like an equalizing line between the two intakes if it remains connected.
Anyway, thanks for any help.