Pilot Screws

[GaryZ]

Recently I sealed a fuel leak on one carb. During testing I noticed one carb slide was lagging behind the others (bad diaphragm). For the moment I have repaired the diaphragm with silicone. The bike was running rough after the repair, leading me to believe the synch was probably off.

 

My home-made synch tool verified that the carbs were off and I made adjustments. The bike did not seem to properly respond to these adjustments. I decided to pull the pilot screws caps and check the settings. It has been said that a general setting for the pilot screws would be 2.25 turns out. I found mine to be between 3.25 and 3.75!

 

My thinking is that after 24 years and 63,000+ miles, these screws must have backed out on their own. I adjusted all of them to 2.5 turns out and took my wife to dinner (45 mile round-trip). The bike is running much smoother below 4k and seems to have better torque.

 

Comments from the gallery?

[Shamue]

just information, unless silicone is specifically made to seal fuel areas it should not be used. I know permatex used to make one. If it does not specifically say for fuel, the silicone WILL ALWAYS get saturated by the fuel and turn into very very small beads and infiltrate you carbs and intake into the engine causing what you describe and even worse.

How Do I Know This,,, talked to a permatex rep. that verified as much after a friend of mine used permatex to seal up a carburator on a drag car as a quick fix instead of a gasket. Car ran like Crap. Had to dip and rebuild the carb, clean out the intake and flushed the fuel system. Found alot of pin head size silicone bee bees plugging up the carb not much in the intake, none in the fuel system, but changed the fuel filter anyway.

Car was back on the track, that afternoon.

Just a thought

[camos]

When it comes to pilot screw adjustments, 2 1/2 turns out is not a particularly magic number. That number of turns out is only broadly meant to get the motor running. Fine tuning by 1/4 or 1/8 turns from there to find the sweet spot. Do one carb at a time turning in or out as it may require until hearing a roughness in the engine then turn it back 1/8 turn should get to the right spot.

 

The pilot jet sets the air/fuel mix for the idle circuit. For this adjustment to be most effective the carbs need to be in sync and clean with no gobbed up o-rings.

 

If the adjustment is way off the 2 1/2 turns then there are at the very least, minor problems with the air or fuel delivery. I think more often than not, some crud and somewhat degraded o-rings cause over compensation when adjusting the pilot jets.

 

Cheers

Clive

[GaryZ]

Checked fuel mileage this morning. After the adjustments and the smoother running I expected an improvement . . . No change! Maybe its my right wrist