Raptor pilots and fuel screws
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07-26-2002, 04:02 PM
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Ok, for those who care to know...
When I did the cam break in on my Trinity 686 my jetting was stock 22.5 pilots, 3 turns out on the screws, 180/185 main jets, needles in 4th clip position.
after 20 minutes at 2,000 rpm for the cam break in I changed oil and filter and checked the plug. Plug was dark brown.
next I rode up and down the street a few times and had the notorious backfire on deceleration. I backed out the screws some more and it was slightly better.
Even though the 2,000 rpm cam break in told me the pilot circuit was ok...I decided to up my pilots to 25's to see if it would run better due to the backfire on decel.
I rode at 3,000 feet and my plug was black and I played with the fuel screws to the point things got worse. Also had a slight stumble at mid throttle.
Back home at sea level I decided to go back to stock pilots and lower my mains to 175/180 for some higher altitude riding tomorrow.
Guess what!!! When I had the carbs off I could see that the needle of one of my fuel screws had lodged in the hole and broken off!! When I turn the fuel screw the screw would turn but the needle was stuck in the hole and blocking the circuit entirely!!
Moral of the story....LIGHTLY turn your screws in until they stop. I obviously went too far and lodged the needle in the hole and when I backed the screw out the needle snaped off and stayed in the hole. [img]i/expressions/face-icon-small-sad.gif[/img]
If you use a flexible screwdriver you lose "feeling and touch" because of all the angles and girth of the screwdirver.
I think the 22.5 pilots will be rich enough for sea level at 3-4 turns out and can be adjusted for altitude.
Now I have to wait 3 business days for Yamaha to ship my $10 screw [img]i/expressions/face-icon-small-sad.gif[/img]
Picture of pilot/fuel screw
When I did the cam break in on my Trinity 686 my jetting was stock 22.5 pilots, 3 turns out on the screws, 180/185 main jets, needles in 4th clip position.
after 20 minutes at 2,000 rpm for the cam break in I changed oil and filter and checked the plug. Plug was dark brown.
next I rode up and down the street a few times and had the notorious backfire on deceleration. I backed out the screws some more and it was slightly better.
Even though the 2,000 rpm cam break in told me the pilot circuit was ok...I decided to up my pilots to 25's to see if it would run better due to the backfire on decel.
I rode at 3,000 feet and my plug was black and I played with the fuel screws to the point things got worse. Also had a slight stumble at mid throttle.
Back home at sea level I decided to go back to stock pilots and lower my mains to 175/180 for some higher altitude riding tomorrow.
Guess what!!! When I had the carbs off I could see that the needle of one of my fuel screws had lodged in the hole and broken off!! When I turn the fuel screw the screw would turn but the needle was stuck in the hole and blocking the circuit entirely!!
Moral of the story....LIGHTLY turn your screws in until they stop. I obviously went too far and lodged the needle in the hole and when I backed the screw out the needle snaped off and stayed in the hole. [img]i/expressions/face-icon-small-sad.gif[/img]
If you use a flexible screwdriver you lose "feeling and touch" because of all the angles and girth of the screwdirver.
I think the 22.5 pilots will be rich enough for sea level at 3-4 turns out and can be adjusted for altitude.
Now I have to wait 3 business days for Yamaha to ship my $10 screw [img]i/expressions/face-icon-small-sad.gif[/img]
Picture of pilot/fuel screw
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