Pilot or Needle?

-D. Dwarf

Ok, I know it's a tad off topic, but how was that 5 seconds full throttle and then back to 3/4 throttle and see if it gains speed test again? That was done in top gear I remember, and if it gains speed after backing off a little the main jet is what? Too small or too big? And at what speed/rpm is it recommended to the test?

Ok I guess I did it right already. Couldn't feel any acceleration while backing off. So seems I'm fine with the stock 145. I had the 150 in before and it fouled the plug.

Routy wrote on 09/02/10 at 12:42:43:


I was under the impression that the exact opposite was true. The amount of fuel flowing through the main jet is being metered by the needle when the throttle is mostly closed. Increasing the size of the main jet shouldn't allow more fuel past the needle.

Of course, I'm usually wrong when it comes to carburetors.

-D. Dwarf

DrunkenDwarf wrote on 09/02/10 at 07:04:15:


the pilot jet is the primary control for idle to 1/4 throttle
needle jet & jet needle ... 1/4 to 3/4 throttle
main jet .... 3/4 throttle to W/O (wide open)

*there is of course overlap between the 3 major fuel circuits above, but for basic purposes that is the way a carb works

THIS IS THE GENERAL RULE OF THUMB FOR ALL MOTORCYCLE CARBURETORS

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1267299409

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1262724030/0

DrunkenDwarf wrote on 09/02/10 at 20:27:20:



YEP ...when talking about the stock carb, turning the pilot air adjusting screw 'out" (CCW) richens the mixture.  You never want to go more than 3 turns out lest the screw drop out on you.  If the engine still acts lean at 3 turns out then go up 1 size on the pilot jet and start over with the screw adjustments

ralfyguy wrote on 09/03/10 at 04:40:26:


not sure about a chart...I have vague shadows in my mind but have no idea if it is the chart you want
I do not have this info on hand right now but will try to find out.
...ever seen a drill bit small enough to use for a pilot jet ? ?   not me

there are sets of tiny files, some regular and some diamond coated, but the sets are basically the same size and shape
the round pointed file can be used VERY CAREFULLY to enlarge the hole in a jet
just keep in mind that the jet is made of brass and is very soft compared to the file
insert the point of the file in the hole of the jet and rotate the file with your finger tips GENTLY once or twice and then check it

I try to find a wire that just barely goes through the hole of the jet, so I have something to use to compare after each filing...does it go through about the same or is it easier ?
if it feels like the hole is slightly larger then install in the carb and test it.

the holes are so small to begin with that it does not take much at all to change the fuel flow a LOT, so go slow and easy

The first time I tried this I filed the hole until I could SEE that it was larger.....  at that point I had already jumped 3-4 jet sizes, so DO NOT GO BY HOW IT LOOKS ...find a wire that just barely fits and judge by how it feels going in and out.

LANCER wrote on 09/02/10 at 14:57:23:


I've got a couple questions about these links.

First, the stock white spacer in my carburetor was 2.8 mm and the washers you sent me were 0.5mm thick. The end result is the same number of suggested washers, but the thicknesses are different that you posted.

Second, what's 4000 rpm in 4th gear work out to be in mph (assume stock tire/belt/etc).

-D. Dwarf