What will lean my bike out?

[nastyjones]

I remember last year before I put my 80 gs1100 away that it seemed to run rich when at steady throttle in the lower gears about 3 grand or so. I have pods & a free running pipe on an otherwise stock motor. I am running 130 mains, 160 pilots & 47.5 air jets. Should I go down a size on the pilots or air jets?

[tkent02]

It seemed to run rich, or it was running rich? Did you do a series of plug chops or are you just going by guess and by golly?

Try one size smaller on the pilots.

[nastyjones]

Did the plug chops & they indicated a rich mix.

[1_v8_merc]

I thought our bikes were barely out of the Pilots by 3k!

I would get the bike up to an average cruising Rpm like 4-7k.
Chop it, and see what you come up with.

My bike feels boggy as **** and runs fairly rich at 3k, as well.

Im wondering if you're getting a partial-pilot reading instead of Main?

[tkent02]

The main jet won't do anything until nearly full throttle. The needle and needle jet won't do much until 1/4 or so and above throttle up until where the main takes over.

Steady throttle in the low gears about three grand or so is all on the pilot.

[banditom]

mix up in numbers, smaller pilots

quote,,,,160 pilots & 47.5 air jets,, unquote

Not to belabor things, but I think you have the numbers mixed up as to airjets and pilot jets.

1,,And I think going up LARGER instead of smaller one size on the air jet will tend to lean it out a bit, but see below too. Check 2 and 3 first though.

2,,Are you sure that the floats are set correctly??

3,,Does your model carb have that rubber plug over the pilot jet, and is it still in place?? If its sposed to be there, and isnt, I think that could cause a rich run.

4,,If you can be sure that 1,, 2,, n 3 are right, and if you can be sure you have a rich run, below or at three thousand, me thinks you want to reduce the pilots one step, unless someone comes up with something that I am not thinking about.

[nastyjones]

quote,,,,160 pilots & 47.5 air jets,, unquote

Not to belabor things, but I think you have the numbers mixed up as to airjets and pilot jets.

1,,And I think going up LARGER instead of smaller one size on the air jet will tend to lean it out a bit, but see below too. Check 2 and 3 first though.

2,,Are you sure that the floats are set correctly??

3,,Does your model carb have that rubber plug over the pilot jet, and is it still in place?? If its sposed to be there, and isnt, I think that could cause a rich run.

4,,If you can be sure that 1,, 2,, n 3 are right, and if you can be sure you have a rich run, below or at three thousand, me thinks you want to reduce the pilots one step, unless someone comes up with something that I am not thinking about.

According to Bikecliff's website, I calling the pilot & air jets by their correct name.

Floats are set properly & rubber plugs are in place so you think installing 150 pilots will help?

Forgot to mention, needles have been raised 1 notch

[TheCafeKid]

Nope. 47.5 is the pilot. 160 is the air jet. And you're not going to get it run right with pods and a pipe with the stock needles. You can put whatever jets you want in there and somewhere you're going to have a problem. You've got it to run partly because you've put a very large main in there with a larger than stock pilot. But as you can see, you have wet sloggy bottom end. Bite the bullet and buy a DynoJet kit, install it, and realize that the bike has way more power than you thought because it's been either starving or drowning in one circuit or another. Believe me, I've been through this more than a time or two. The stock needles will NOT work with that set up.

[posplayr]

The main jet won't do anything until nearly full throttle. The needle and needle jet won't do much until 1/4 or so and above throttle up until where the main takes over.

Steady throttle in the low gears about three grand or so is all on the pilot.

I just finished jetting my 81 GS750EX, it is bone stock except for two items. It has a K&N filter in the stock airbox which made it tend to run on the lean side even though ridability was good and it started very well. After putting in a 1100EZ intake cam, the low end hesitation (2000-3000 or surging at 2500 rpm) and surging got much worse. Richening the needle up 1 groove (equivalent with spacers) did not seems to help much at all.

Finally I swapped out the stock Mikuni 112.5 and put in a Dynojet 124 which is close to a 116 Mikuni . Cleaned up almost the whole bottom end surging problem. I did not change anything else. New plugs now have a hint of soot at the bottom of the insulator. My AFR gauge would not work properly with that old R/R on the GS750.

Top end was still strong to 7K rpm which is about as high as I took it during break in.


So it seems that the bigger main had some effect even at the low end.

[posplayr]

Nope. 47.5 is the pilot. 160 is the air jet. And you're not going to get it run right with pods and a pipe with the stock needles. You can put whatever jets you want in there and somewhere you're going to have a problem. You've got it to run partly because you've put a very large main in there with a larger than stock pilot. But as you can see, you have wet sloggy bottom end. Bite the bullet and buy a DynoJet kit, install it, and realize that the bike has way more power than you thought because it's been either starving or drowning in one circuit or another. Believe me, I've been through this more than a time or two. The stock needles will NOT work with that set up.

Agree

Mikuni 130 is equivalent to Dynojet 138 which is the fatter jet in the jet kit. It is also standard to bump up the Pilot for 45 to 47.5 (if you have a 4:1; with my 4:2:1 I had to go back to a 45)


That setup is just about right except for the needles. Need to get some tappered needles; Rapidray will sell the needles alone.

[koolaid_kid]

I wondered about the main jet statement. My needle rides in the main jet as far as I can tell. The fuel outlet area is the difference between the inside diameter of the main and the outside diameter of the tapered needle, depending on its position. So I would expect a larger main jet to have an effect on the needle performance, even though the main is not the only source of fuel, such as WOT. I think of it as a hole we are sticking a tapered needle into. If the diameter of the hole ls larger, would it not have an effect on the throughput of the needle range, versus a smaller diameter hole?
IMHO, I believe this is the reason that we tune our carbs main jets first, then the needle, because the ID of the main has an effect on the needle performance.