I bought a bike that someone had obvously been messing with the throttle body stops. The paint was broken on one of the lock screws and they were being difficult to balance so I stripped them off and decided to give them a clean-up and set the stops so they were the same. This is important because it allows the idle to be adjusted using the air screw and prevents you from messing up the idle-up (choke lever) operation by having to over-adjust the cable adjusters for the second half of throttle body balancing.
Anyway the process is very simple. First, remove the throttle bodies from the bike, might as well give them a good clean-up whilst they are off I use brake cleaner to wash the dirt and grit out of the return spring and outside surfaces, and iron fallout remover (iron-x, iron-out) for cleaning the black residue that coats the throttle blades/inisdes, and don't forget to remove the brass air screw and clean the gunge out of there because they tend to get a coating of black gunge with time.
Here's my method for setting both of the throttle body so the blades are open the same amount when the throttle is 'shut'.
You might want to do this adjustment if you find that your throttles have been messed with or if you have a few miles on the bike and the throttles are a bit worn. On very high mileage bikes the throttles tend to rattle quite loudly because the bushes are worn in the throttle body. When this happens I strip out the butterflies and shafts and press in new poly bushes and then this procedure would be required to re-set the stops after that.
Once this was all done I adjusted the throttle body cable adjuster so that the idle-up lever was pulling the quadrants the same amount (by eye) then went on to balance the throttles via the usual procedure.
Anyway, I hope that someone finds this useful. if it heps one person it was worth the time to write it up.
Pete.
Anyway the process is very simple. First, remove the throttle bodies from the bike, might as well give them a good clean-up whilst they are off I use brake cleaner to wash the dirt and grit out of the return spring and outside surfaces, and iron fallout remover (iron-x, iron-out) for cleaning the black residue that coats the throttle blades/inisdes, and don't forget to remove the brass air screw and clean the gunge out of there because they tend to get a coating of black gunge with time.
Here's my method for setting both of the throttle body so the blades are open the same amount when the throttle is 'shut'.
- Back off the throttle stop so that there is a clear gap. Gently flick the quadrant so that the throttle blade shuts tight in the throttle body, but don't do it so hard that it sticks in place.
- Take your digital caliper and measure across the slot in the quadrant and the lug for the throttle stop screw as shown below. Once you have done that, zero the caliper. I measured tight in line with the middle of the screw, it doesn't matter so much where you measure so long as you take both measurements in the same place any try to hold the caliper as near as possible to level.
- Now adjust the stop so that your caliper is reading 1.3mm This was the ideal setting for my bike, you might want to go up or down a bit but the only real important thing is that 1. both throttle bodies are the same and 2. once fitted, you are able to adjust the idle on the air screws. I found that 1.3mm on the throttle stops and 1.5 turns on the air screws allowed my bike to start and idle right off the bat and only a tiny amount of adjustment was required on the vacuum gauges.
You might want to do this adjustment if you find that your throttles have been messed with or if you have a few miles on the bike and the throttles are a bit worn. On very high mileage bikes the throttles tend to rattle quite loudly because the bushes are worn in the throttle body. When this happens I strip out the butterflies and shafts and press in new poly bushes and then this procedure would be required to re-set the stops after that.
Once this was all done I adjusted the throttle body cable adjuster so that the idle-up lever was pulling the quadrants the same amount (by eye) then went on to balance the throttles via the usual procedure.
Anyway, I hope that someone finds this useful. if it heps one person it was worth the time to write it up.
Pete.
