Pilot jets sorted the problem

[dickbarton]

I said I'd let this forum know how I got on with a new B12 that was running too lean. Well it took three weeks to get some new pilot jets ordered from Japan. They were 20's to replace the production 15's.

Its made all the difference in the world. It now runs much smoother on a partial throttle, and means I dont have to accelerate everywhere if I dont want to. Problem is, it now runs so well that I do!!!


The bike is standard apart from that, but hooo boy does it ever shift, and it goes round corners like a rat up a drainpipe.[/b]

[GSF1200S]

Do you have a 2005?  Do you have a slipon or stock exhaust?  Did they change the main jets?

Sorry for all the questions' I have an 05 that seems to run lean

[dickbarton]

Yes 2005 special edition.
Everything is standard.
Suzuki apparently changed pilot jet size from 20 to 15 a while ago on new bikes, to meet emission regs. All my dealer did is change them back.

[GSF1200S]

Did they cover it under Warranty?

[dickbarton]

Yes and they did the first service with no labour charge because of the inconvenience.

[GSF1200S]

Hi Dick,

Do you know know the suzuki (or aftermarket number) for the #20 Mikuni Pilot Jet?

Thanks,

Keith

[GSF1200S]

BUmp

[Red01]

Hi Dick,

Do you know know the suzuki (or aftermarket number) for the #20 Mikuni Pilot Jet?

Thanks,

Keith

Mikuni p/n: VM28/486 + size

I've heard good things about Carb Parts Warehouse - put couldn't find any specifics, like prices for various parts, so you'd have to contact them.

Also heard good things about Sudco and they list the VM28/486 #20 as p/n 004-030 ($3 each)

Also worth considering is the #27.5 recommended on Fast Larry's Bandit FAQ. (Sudco p/n 004-033, also $3/ea.)

[GSF1200S]

I'm using the stock muffler right now.  Do you think the 27.5's would be too rich?

Thanks for your reply!

Keith

[Red01]

The 27.5 is probably too much for a stock pipe.

[GSF1200S]

Hello All,

I followed Dick's advice on my 05 1200S.  Runs great with the 20's.  Main difference is there is no longer a lean spot off idle on acceleration.  Very noticable improvement in low speed cornering.

 

[Bazza]

I have installed 17.5 pilots in mine and a good rule to follow with pilot jets that someone posted here is.

If you can obtain a good idle with the a/f screws being no more than
3 1/2 turns out you don't need to change them. If you are anymore than 3 1/2 turns out go with the next size pilots.

From what I have seen, after 3 1/2 turns the metering of the a/f screws becomes less accurate. The 17.5's in mine work well, and would probably work great with a stock bike.

In essance going up a size in pilot jets is like opening up the a/f screws more.

Just as a comparo (and this is a rough example and by no means accurate) The larger pilots get you the same a/f mixture with less turns out on the screws.

15   Pilots 3 1/2 turns
17.5 Pilots 3 turns
20.0 Pilots 2 1/2 turns out

Larger Pilots do help you obtain a smoother idle.

[GSF1200S]

This advice is based on the assumption that the pilot jets only feed the idle circuit.  This advice, while well intentioned is incorrect.

There is also a transfer slot (Part of the low speed circuit) that straddles the bore opening at the throttle plate.  This bridges the gap between the Idle Cicuit (Mixture Screw) and the Main Circuit (Main Jet).  As the the throttle plate is opened is draws fuel from this slot (as well as the idle cicuit) until the slide lifts and fuel is delivered from the main jet.

A review of the carburetor design will show this.

[rspector]

my 05 bandit 1200, doesn't seem to be running lean or stumbling off the line?

[Dave 02 1200]

The Holeshot Stage 1 jet kit includes a #17.5 pilot jet.  However, Dale recommends starting with the stock #15 pilot jet and with the screws out 3.75 turns as a base setting for a stock motor with stock exhaust.  That is what I did, along with #107.5 main jets and 4 shims under the needles.  Results are great.