This data has been gathered from old out-of-print material. While we make every effort to be accurate, the information shown is to be used for general reference only. It is always best to have the original service or operator's manual for your tractor before attempting any tuneup.

There is a legend at the bottom of the page describing some of the terms used here.

Model	Point Gap	Spark Plug Gap	Timing Mark On	Spark Occurs	Firing Order	Int. Valve Clearance	Exh. Valve Clearance	Comments
M,MT	.020	.025	FLY	TDC	1-2	.012C	.012C	For magneto set point gap to .015
L,LA	.020	.025	FLY	TDC	1-2	.006H	.008H	For magneto set point gap to .015
H (All Fuel)	.015	.030	FLY		1-2	.015H	.015H	Spark occurs when dot or "LH-Impluse" aligns with index on cover or case.
G (All Fuel)	.021	.030	FLY		1-2	.020H	.020H	For magneto set point gap to .015 - Spark occurs when dot or "LH-Impulse" aligns with index on cover or case.
D (All Fuel)	.015	.030	FLY		1-2	.030H	.030H	Spark occurs when dot or "LH-Impluse" aligns with index on cover or case.
B (All Fuel & Gas)	.015	.030	FLY		1-2	.020H	.020H	Spark occurs when dot or "LH-Impluse" aligns with index on cover or case.
A (All Fuel & Gas)	.021	.030	FLY		1-2	.020H	.020H	For magneto set point gap to .015 - Spark occurs when dot or "LH-Impulse" aligns with index on cover or case.
80 Cranking Engine	.020	.025	FLY	30 deg. BTDC	1-2-3-4
70 Cranking Engine	.020	.025	FLY	30 deg. BTDC	1-2-3-4	.020H	.020H
70 (LP), 60 (LP)	.022	.030	FLY	5 deg ATDC	1-2	.020H	.020H
70 (Gas)	.022	.030	FLY	10 deg. ATDC	1-2	.020H	.020H
70 (All Fuel), 60 (All Fuel)	.022	.030	FLY	TDC	1-2	.020H	.020H
50 & 60 (LP & Gas)	.022	.030	FLY	5 deg ATDC	1-2	.020H	.020H
50 (All Fuel)	.022	.030	FLY	TDC	1-2	.020H	.020H	For point gap, for LP set TDC.
40 (All Fuel)	.022	.025	FLY	3 deg ATDC	1-2	.012C	.012C	For point gap, for LP set TDC.

Legend
TDC - Top Dead Center FP - Crankshaft Fan Drive Pulley Exh - Exhaust Int - Intake ATDC - After Top Dead Center BTDC - Before Top Dead Center
Data collected from an old Niehoff tune-up chart.

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