Carburettor settings for your KTM 620 LC4

The correct carburettor setting is essential for a good-running KTM 620 LC4. So that you don't ruin your engine with an incorrect carburettor setting and get unrestricted riding pleasure from your Mattighofener bike, we would like to give you an understanding of the correct carburettor setting.

The basic setting

The basic setting of your carburettor is the starting point for any adjustment work. Especially in the case of heavily adjusted carburettor setups that do not work at all, it is therefore advisable to return to the standard and make any necessary adjustments from there.

	KTM 620 Super Competition (SC) 20 kW	KTM 620 SX / Super Competition (SC)	KTM 620 EGS Classic without SLS	KTM 620 EGS Classic with SLS
carburettor type	PHM 40 SD	PHM 40 SD	PHM 40 SD	PHM 40 SD
Main nozzle	155	195	170	155
needle nozzle	DR 268	DR 272	DR 268	DR 268
idle nozzle	45	45	45	45
jet needle	K51	K51	K51	K51
Needle position (from top)	III	II	III	III
Mixture adjusting screw (turns open)	1, 5	1, 5	1, 5	1, 5
gas slide	40	40	40	40
Start nozzle	45	45	45	45
throttling	Slide stop 26 mm	-	-	-

Adjustments

If you notice that your KTM 620 LC4 is not running properly, you may need to make adjustments. This is especially necessary in very warm and very cold temperatures, but also when riding at altitude or with tuning measures

Warm temperatures: the air contains less oxygen, the combustion in the engine runs worse. Now a smaller main jet can improve the driving performance. Adjust in individual stages according to the spare parts catalogue when the engine is warmed up.
Cold temperatures: the air now contains more oxygen, combustion in the engine now runs better. A larger main jet may now be necessary to avoid damage to the engine (often noticeable by the engine not revving properly).
Tuning measures: generally bring an increase in performance, for this it usually requires a richer jetting of the main jet (and rarely idle jet).
Altitude: the oxygen content of the air also varies depending on the altitude in which you are located. Therefore, at higher altitudes you should jet a little leaner, at lower altitudes a little richer, first try changes to the main jet.

The constants & tuning

As you can see, there are also many constants in the carburettor tuning. KTM itself never changes the throttle slide (always 40s), the air mixture screw (always 1.5 turns open) or the jet needle (always the K51 needle) in the different power classes. As a rule, you also do not touch the start nozzle.

In exceptional cases, if your motorbike does not run properly in the 0-1/4 throttle range, an adjustment of the idle nozzle can help. However, this is almost never the case. The tuning of your KTM 620 LC4 is almost exclusively done by adjusting the main jet, in a few cases a correspondingly larger or smaller needle jet may also be needed if the main jet is significantly larger or smaller.