Question about 2003 Suzuki RM 125

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What size is the main jet in an 03 RM125 - 2003 Suzuki RM 125

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The stock plug is an NGK R6918B8. At only $22 each.
what size is the main jet in an 03 RM125 - 44ef13e.png

Posted on Jul 30, 2009

  • tombones Aug 14, 2009

    Man, did I mess up an answer or what. I am extremely sorry for my blunder. I gave you an answer to a question someone else had just asked. I am surprised you ranked he answer as "somewhat helpful". A better rank would have beed "not helpful". Let me try again.

    The RM125 has many choices for main jets. There are six models of the RM125 and a couple of "sub" models as well. The jet needle has just as many choices.

    Models K1 and K2 get a 460 stock jet. Optional jets range from 400 through 600

    Model K3 gets a 460 stock jet on the E3 and a 560 on the E28 Optional jets range from 400 through 600

    Model K4 gets a 390 stock jet on the E3 and a 460 on the E28 Optional jets range from 300 through 500

    Model K5 gets a 370 stock jet on the E3 and a 390 on the E28 Optional jets range from 300 through 500

    Model K6 gets a 370 stock jet. Optional jets range from 300 through 500


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Posted on Nov 08, 2009

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1 Answer

Main jet size

Bigger jet is not the problem. More fuel would be put in and you said that it runs well at the top end. So it is not a fuel shortage issue.

May 28, 2015 | 2005 Yamaha DT 125 RE

1 Answer

I have a 1980 rm125 and I have a 140 main jet on it is that the right jet or if not please tell me the right stock jetting.

You should really have the workshop manual if you are working on the carb. Not only will this tell you the correct main jet size, you will also get the pilot jet size, mixture screw, and jet needle positions. All of these should be checked if you're taking apart the carb yea?

Mar 10, 2015 | Motorcycles

1 Answer

Factory Jet Sizes

Front cylinder carburetor:

112.5 Main Jet

17.5 Pilot Jet

(1) 0.020" thick shim washer under the needle

PMS setting apparently varies from bike to bike... but it should be 2.5 turns

Rear cylinder carburetor:

110 Main Jet

17.5 Pilot Jet

(1) 0.020" thick shim washer under the needle

PMS setting apparently varies from bike to bike... but it should be 2.5 turns

May 23, 2013 | 2000 Yamaha V Star 1100 Classic

1 Answer

Fuel line routing



Fine tune your motorcycle before rejetting your carburetor. If it's still running too lean, you can replace the pilot jet as a first step

Remove the bowl at the base of the carburetor by unscrewing the screws holding it in place. Unscrew the pilot jet inside, but be careful not to strip it. The jet size will be on top.

5 Year/ unlimited mile warranty No up front core charge

Use a screwdriver to remove the main jet from the brass jet needle holder, which is also called the emulsion tube.

Put in a pilot jet that is one size larger. Replacing it with a jet two sizes larger will make your mixture too rich.

Tune the slow/idle settings before replacing the main jet. Replace the main jet with one size larger. The sizes are in increments of 5.

Put the bowl back on, and align the accelerator pump shaft and rubber boot.

Reinstall the carburetor on the motorcycle and retune it to finish the rejet procedure.

Jan 11, 2013 | 1998 Honda VT 600 C Shadow

1 Answer

I had the muffler baffles shortened on my 03 C2 to get a better sound but now it backfires badly.Is there some mod to the carbs i can do????

ok u have better fuel flow with the shortened exhaust you will most likely need to go up a main jet size ur running with too much air in ur mixture running hot and the backfires are when u get to top of ur gear range its starveing it of fuel runing too hot the exhaust is geting super heated and the backfires are as u decelerate right ? thats unburnt fuel hiting ur exhaust and going bang u may even notice flames at exhaust tip the new slightly larger main jet shuld fix this you may have to ajust the main needles up or down to compensate for the jet change asumeing they are adjustable the pilot jet shuld be fine no need to touch anything there

ok so as u running now ur fuel cat emission thing eats petrol and vice versa over fuel a lot the cat will be overwelmed and get eaten by the fuel ur at the other end too much air cat wont be effected but as ur running much hoter then needed your basicly eating your engine from the inside out from the aditional air the new main jet will allow more fuel from the start of midrange to top end u shuld find after this fix the bike will run stronger and faster and cooler from 600 rpm up primerily more at top end

the main jet is the fix as far as i see it but like i say ajusting that to allow more fuel means u also effect midrange to have more fuel more so the more u open the accelorator so you may need to make a minor adjustment positioning ur needles prehaps 1 clip up putting the needle its self a bit closer to the jet thus giving less fuel thats if you have ajustable needles if not u cant ajust midrange but to be honest just that pilot jet shuld put u so close to right u may not even need the midrange ajustment try it 1 size up on all main jets its at the least a big step in the right direction if not a total fix

hope this helps

Oct 29, 2012 | 2003 Honda VT 1100 C2 Shadow Sabre

1 Answer

Mileage problem

Hi Patrick, you can start by going to smaller main jets untill you notice poor performance then go up one size, and the usual suspects are:
1. Excessive use of enrichner system.
2. Enrichner valve not seated or leaking
3. Dirty air cleaner element.
4. Restricted fuel tank vent system.
5. High speed riding style.
6. Idle speed improperly adjusted.
7. Loose jets.
8. Float level too high.
9. Plugged or restricted bowl vent.
10. Worn or damaged needle or needle jet.
11. Vacuum piston assembly malfunction.
12. Plugged air jets or passages.
13. Excessive accelerator pump output.
Good luck and have nice day.

May 12, 2012 | Harley Davidson Motorcycles

1 Answer

What is the size of main jet of YZ125?

  • Main Jet: 410
  • Main Air Jet: 2.5
  • Jet Needle: 6BFY43-74
  • Needle Jet: S-1
  • Pilot Air Jet 1: #40
  • Pilot Outlet: 0.7
  • Pilot Jet: 40

Jun 05, 2011 | 2003 Yamaha YZ 125

1 Answer

Engine revs up while idling

Check the Exhaust Valve actuating rod is firmly in it's bush and the actuating arm is screwed to the valve actuator...the diagram on this link below refers.

Have you looked closely for air leaks between carby and engine, airbox obstructions or wrong sized pilot jet? Choke plunger thread not loose allowing extra fuel to surge through? Try turning air mixture screw IN half turn. The site below has the complete bike in exploded diagrams. Hope this all helps, good luck.

May 10, 2010 | 2003 Suzuki RM 125

1 Answer

My rm125 spews oil out of the exhaust

Are you running 32/1?
You should be, and then jet to match that.
If you pilot, or idle jet is too big, you will have a black plug at idle.
If your main jet is too big, you will have a black plug from 3/4 throttle to full. You want the plug color like chocolate brown. (White is too lean)
The needle jet clip cover between the pilot and main jet.

Mar 19, 2010 | 2003 Suzuki RM 125

1 Answer

Main jet sizes

The sizes are stamped on the Jet it self. For the Honda Shadow it is a 185. Not sure for the steed.

Jan 12, 2009 | 1990 Honda VT 600 C Shadow

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