3/4 throttle responds better than full throttle on highway.

[Johnny K]

My sig is my bike. Everything is great, but just out of curiosity when I am on the highway in 5th gear and click down to 4th, full throttle then click it back to 5th and full throttle after about 10 seconds or so if I back the throttle to about 3/4, it responds better than full throttle. How come?

[andmoon]

OH OH I know I know. Finally a non Q post for me!


I just became an expert on the last 1/4 of the throttle.

Go down one size on the main jet.


My 83 went from not taking full throttle to stumbling, surging, accelerating, accelerating as hard as almost full throttle and finally accelerating as hard as she will (I think/hope)....each step going down main jet size.

Ballpark... issues when you are asking the bike for power ...rich
issues when you are asking to maintain speed ...lean

By the end of the series of throttle inputs you described, starting ~ 65mph, my bike is well into triple digit speeds.

[tkent02]

Because your main jet is too small. It runs better without all the airflow of full throttle, it only gets enough gas for 3/4.

It could also be the other way, main too large so it runs better when the needle is part way down, reducing the fuel.

I had both of these conditions last week, playing with the jetting on a GS1100E up in the mountains. They both feel similar. They sound different, too rich will be likely sputtering and popping, too lean more like surging. My 1100 has the stock exhaust and airbox, so could not really hear the difference, had to pull plugs to determine rich or lean.

What color are your plugs after doing this and chopping the engine?

You have pods and a pipe, it will take lots of plug chops to get it just right.

[chef1366]

Because your main jet is too small. It runs better without all the airflow of full throttle, it only gets enough gas for 3/4.

It could also be the other way, main too large so it runs better when the needle is part way down, reducing the fuel.

I had both of these conditions last week, playing with the jetting on a GS1100E up in the mountains. They both feel similar. They sound different, too rich will be likely sputtering and popping, too lean more like surging. My 1100 has the stock exhaust and airbox, so could not really hear the difference, had to pull plugs to determine rich or lean.

What color are your plugs after doing this and chopping the engine?

You have pods and a pipe, it will take lots of plug chops to get it just right.

Couldn't of said it any better.
Bingo

[Johnny K]

Yeah, I know that having pods and a pipe is a PITA to get right, haven't checked the plugs and have been turning out the mixture screws a tiny bit out because I have had slight popping on decal. I'm pretty sure they are at least 3 turns out. I have reached a rich stage because of the tiny "gas smell" out of the exhaust. Better rich than lean I go for. I have always had a slight stumble when giving it tiny throttle when letting out the clutch. I blip a tiny bit before letting out the clutch and it's fine. When going I can blip the throttle and the response is a crisp jerking due to quickly throttling off and on (it's a good thing). So I am not sure if these two are related to the main jet size or not.

[jabberjoe87]

i agree on the jet size as well, full throttle is the main jet squirting. the screws are the off idle screws i beleive and will not help at full throttle