Lean idle fix/concerns

[Travis Moore]

This year on my Bender II RX1, my idle A/F ratio seems to be very lean (somewhere around 18/1), although from the VERY limited riding I have been able to the WOT a/f ratio seems to be fine-not sure about the midrange. I have number 15 pilot jets in the carbs and 132.5 main jets. I do have the stock 17.5 pilot jets set aside also. Should I put those back in, make a diffrent adjustment, or just leave it alone?

Definitly not a carb expert

Thanks!
T

 

[BigDog05]

Travis: It totally confuses me how all these sleds run different jetting.

Mine ran lean with 17.5's at 2 1/2 turns. I thought for sure it was a clogged pilot jet.

When I first put mine together and it was popping out the exhaust, Bender told me to run 15's at 2 turns. Tried that for about 1 hour. I was up around
19's at idle.

I then went to 20's @ 2 turns and it idles @ about 16.5 until it warms up to about 175-180 then it settles in at about 14.7-15.0.

Only thought would be if it was ok last year, then it might me a clogged pilot jet.

This is just running sled on the stand this year. I always let it run up to about 195-200 when running on the stand to get all moisture out of it.

 

[Travis Moore]

Travis: It totally confuses me how all these sleds run different jetting.

Mine ran lean with 17.5's at 2 1/2 turns. I thought for sure it was a clogged pilot jet.

When I first put mine together and it was popping out the exhaust, Bender told me to run 15's at 2 turns. Tried that for about 1 hour. I was up around
19's at idle.

I then went to 20's @ 2 turns and it idles @ about 16.5 until it warms up to about 175-180 then it settles in at about 14.7-15.0.

Only thought would be if it was ok last year, then it might me a clogged pilot jet.

This is just running sled on the stand this year. I always let it run up to about 195-200 when running on the stand to get all moisture out of it.

My idle AF ratio was fine last year. This year I ran the air filter out the back of the sled and gave each pair of carb slide their own dedicated vaccum source.

I guess I'll try putting the 17.5's back in. I know this is a newbie question, but where are the screws you speak of ("2 turns), what do they do, and are you talking about 2 turns out from bottoming the screw?

T

 

[BigDog05]

Travis: In the Yamaha book they are called pilot screws. Book calls for 2 turns off seat.

I don't know of any way to get to them unless you take the carb rack off and turn carbs upside down.

When you have the carbs upside down, you will see them next to where the carb heater wires attach.

I can see how putting the intake filter outside the seat would lean out higher reving mixture, because you aren't pulling in hot air anymore from the turbo side. I don't know how much it would effect idle though, but it might.

I too added the second line to the slides and I didn't notice at idle, but it did help my lean midrange condition.

I also added green springs last season, but did not get any snow time to check them.

1/2 turn on the pilot screws will make a difference at idle. My understanding from Bender is that they have no effect after 2 an 3/4 turns off seat. That you would have to go to the next size pilot jet at that point.

Problem is that they are such a pain to test and tune.