This list is an unverified listing of Husqvarna engine and frame numbers to be used as a guide in checking older Husqvarna motorcycles for correct number ranges. If you have a Husky that does not match this list and you have good knowledge that it is original, write me an e-mail. 

The second section consists of five characters (VIN positions four to eight) and identify the attributes of the vehicle. For each type of vehicle (passenger cars, MPVs, trucks, buses, trailers, motorcycles or incomplete vehicles other than trailers), different
information is reported.
position 4+5 indicate model like WR, TX, TC, etc
position 6, 7, 8 indicate husky engine size 125, 250, 610,

The third section of the VIN consists of one character which is the "check" digit, a security feature of this numbering system. This character can be numeric or the letter X.

The fourth section consists of eight characters, positions 10-17 of the VIN. The first character, position number 10, represents the vehicle model year.
the following is for 10th position and is the letter designation for year of manufacture -
B=1981, C=1982, D=1983, E=1984, F=1985, G=1986, H=1987, J=1988, K=1989, L=1990, M=1991, N=1992, P=1993, R=1994, S=1995, T=1996, V=1997, W=1998,  X=1999, Y=2000, 1=2001, 2=2002, 3=2003
(NOTE:  I,O,Q, & U are not used! Anytime you see the digit "0" it is a zero, anytime you see the digit "1" it is a one)

Position 11 represents the plant of manufacture.
Positions 12 through 17 form a sequential production number.

Husqvarna Motorcyklar - Kodlista för ramnummer
 

Bokstäver	Nummerserie	Års- modell	Anm.
MF	Alla	1968
MG	"	1969
MH	"	1970
MI	"	1971
MJ	"	1972
MK	00001-10500	1973
MK	10501-19500	1974
MK	19501-	1975	250 WP 125 SE
ML	01000-5999	1975	Övr. 75 års mod.
ML	6000-15999	1976
ML	16000-21999	1977
ML	22000-30999	1978
ML	31000-	1979	125 CR/WR
MM	01000-	1979	Övr. 79 års mod.
MN	01000-	1980
CN/WN/XN	01000-10999	1981	C=CR, W=WR, X=XC
CN/WN/XN	11000-	1982
CO/WO/XO	01000-10999	1983
CO/WO/XO	11000-19599	1984
WO	19600-	1985	WR-mod. med 2 stötdämpare
CP/WP	01000-07999	1985	Övr. 85 års mod.
WP	01000-07999	1985	WR-mod. med "single-shock"
CP/XP/WP	08000-	1986	White tank, white forks
CP/XP/WP	20,000 -	1987	Black tank , grey forks
		1988
		1989
		1990

My thanks to Sven Olof Persson for providing the above listing.

Brief primer on Husqvarna frame/motor number series:

1966 - HVA numbered their 250 motocross bikes with matching frame and engine numbers. The first was #66001and with 300 bikes in the 250 series the last was #66300. The 360 series was started at #66901 and with 50 bikes in this series, the last was #66950. There were at least 50 extra 250 engines produced and given numbers differing from the above. Also several 360 extra engines were produced with unique numbers.

1967 - Husqvarna numbered their 250 motocross bikes with matching frame and engine numbers. The first was #670001 and with many more produced than planned, a 250 could be as high as #671394. The 360 series was started at #6700xx(best guess from my records) and ran thru approximately #671776. The 250T Commandos that were sold in '67 began with number#167001 with the 167 signifying Commando Sportsman and my records show #167155 the last for '67.

1968- Husqvarna initiated a new numbering system to coincide with the new frames, however there were 67's of both sizes leftover and the practice was to overstamp the the 7 in 67 with an 8 and sell in early '68. When the new Huskys arrived these new welded frame models had frame numbers for motocross models that began with MF0001 and the engine numbers did not match the frame anymore. The 250 engines started with 250001, the 360 engines started with 360001 . The Commandos that were sold in 68 started with 168156 and went over 234. Any 67 Commandos were overstamped with an 8.

1969 - The frame numbering system moved up to MG0001 while the engine numbers continued. The new 360 Sportsman had a new series SG0001. The new 400 engines started with 400001.

1970 - The frame numbers moved on to MH and SH. Somewhere in 69-70 the practice of stamping the engine number on the topside at the split line was initiated. The 8 speed option on a factory installed unit was marked with an 8S in the same area as the serial number.

1971 - The frame numbers moved on to MI and SI. Last series of 4 speed and right hand shift.

1972 - The frame numbers moved on to MJ and SJ. New generation 5 speed engines, left hand shift, intro of 125.

1973 - The frame numbers moved on to MK and SK. In 1973 Husqvarna changed the name of the company from Husqvarna Vapenfabriks Aktiebolag (HVA) to Husqvarna AB. The company logo changed as well from the
classic "crown circle" to the modern "gunsight" logo of today(shown on my background).

1974 - The frame numbers remained at MK and SK. Introduction of the "Mag" 250CR

1975 - The new generation Huskys with GP frames were numbered ML, the MK designation was continued on the trail, desert and enduro with the existing standard frame.

I am wanting to improve the accuracy of the above serial number data. All of this above info is from my own experience, contacts with other experienced collectors and factory data from Husqvarna. Please help me add to it for the benefit of all Husky hobbyists. My thanks to Torbjörn Flinck for his help in these and other HVA matters.

Detail facts on 4 speed Husqvarna (please e-mail me more of these):

Ignition coils , flywheel , sparkplug - Bosch, Femsa, Motoplat
Steel wheel rims - Dunlop or Radelli
Alloy rims - Akront
Control levers, throttle, hand grips - Magura levers, Magura #304/305 throttle, Magura small grips w/name.
Tires front and rear - Dunlop Sports 3.00x19 and 4.00x18, Trelleborg T544 3.00x21 and 4.00x18.
Carburetor - Bing 32 mm side float 1/32/5, Bing 54 36mm
Rear suspension units - Girling w/chrome covers and unshrouded adjusters #?
Chain rear drive - Renolds 428
Spokes and nipples -Berg Union
Air filter element - Filtron, Uni, TwinAir