RG500 Carb Balancing
The Rick Lance Way
Adjust all 4 Throttle Stop Screws
Front screw, flush w/ carb body—slot pointing straight up & down.
Back knob, set 3mm gap between knob & carb body.
Slacken all 4 Throttle Cables
That means make them loose. When the twist grip is used to pull on the main throttle cable a little bit the carb slides do NOT move.
Adjust Throttle Cable Free Play
Adjust Throttle Cable ¾ open setting
Rick Lance says it is Very Important to adjust the right side first.
Adjust Oil Pump Cable. Some people like to adjust this so less oil flows to the engine. I think this is a coping mechanism for crappy spark plugs. I think it is false economy to save money on plugs and then spend it on pistons because insufficient lubrication caused them to wear out prematurely.
Gordon Jennings published the only dyno study I’ve even seen comparing oil mix ratios and horsepower. The results were very clear. The results were consistent regardless of oil type. More oil gives more power. Right up to the ratio that starts fouling plugs. There is choice to be made between less oil or better plugs.
My solution is to run premium plugs. The best I’ve found are made by ND. Specifically ND IW-27 Iridium plugs. Do not be fooled by cheap imitators! Other brands have “Iridium” plugs with radically less Iridium than ND has in theirs. Use ND plugs and run the stock oil cable adjustment.
Personally, when I’m going on a really fast ride I add a bit of castor oil to my gas tank, 150:1. It adds a bit of extra protection for when I’m revving the tits off the thing. It also gives everyone behind me a pleasant reminder of my Gamma. People love the smell of burned castor oil.
Screw all 4 Idle Air Screws all the way in.
Set all 4 Idle Air Screws to 1 ½ turn out.
Start engine.
Feel all exhaust pulses & adjust Throttle Stop Screws until each cylinder is working as hard as all the others, while adjusting the Throttle Stop Screws as necessary to obtain good idle.
Perform Final Idle Air Screw adjustment:
a. Ride bike on straight flat level surface at idle with throttle completely shut. Idle along on the carbs only; Throttle Cable must be completely slack.
b. Crack Throttle the least little bit possible and note how the bike responds. Repeat a few times so you are sure of what is happening.
c. Screw all 4 Idle Air Screws all the way in.
d. Turn back out to new setting.
e. Repeat ride test (a-d) until optimal throttle opening behavior is exhibited.
Here’s a detailed writeup on this very important procedure:
It takes a long time. It’s totally worth it.
After Wade Boyd made extensive repairs to three of my four pipes I figured the carbs would need a bit of fiddling. It’s always best to start at the bottom of the carb performance and work towards WFO. So I removed the side panels and went at the air screws.
First off I balanced the throttle cables and screws, just to take those variables out of the equation.
I found a place that is totally flat and has negligible traffic. OK, no place on earth is totally flat, everywhere has some tilt to it. I found a place where the terrain is as flat as a cookie sheet tilted a little bit. This is important because in order to adjust the air screws the bike must be able to move under it’s own power with the throttles TOTALLY closed.
I ran all the tests rolling “downhill” as it is easier to run on a closed throttle that way.
Talk about an exercise in self control. It is hard for me to even think about riding my Gamma at 3mph. Must do it, though.
The trick about air screws is they affect the first little bit of throttle opening. Even 1/8 throttle is too much. In order to test air screws one must be idling in first gear with the throttle totally closed BEFORE the test starts.
I had to open my throttle stop screws another 90 degrees a bit to even reach that point. Once it would roll along with the throttle closed the air screw adjusting began.
The trick is to open the throttle the LEAST LITTLE BIT POSSIBLE and then HOLD IT THERE to see what the bike does. It is really tempting to give a little bit more throttle twist to get it to act normally. Can’t do it or the test is invalidated.
I started out by turning the air screws all the way in then backing them out 1 ½ turns, stock setting. I ride along at idle then crack the throttle a little and see what happens. I have to do this at least ten times to get a reliable reading.
Then I go back and turn the screws all the way in then back them out to the next setting to be tried.
My bike has bigger pilot jets, 27.5, so my next test was to lean it a bit to test if maybe the pilots are a touch too big. I went to 1 ¾ turns out. Stumble was a little worse.
So I went to 1 ¼ turns out. Much better.
Next was 1 turn out. Worse.
Back to 1 ½. Better than 1, still a bit of unevenness though.
1 ¾ again proved going leaner was a mistake.
1 ¼ again and it pulls smoothly.
Put the side panels back on. Went for a ride the next day and initial throttle pickup was much improved. Having the air screws set right really makes coming out of every corner more fun.