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RL250 Serial Numbers

The RL250 was imported into the U.S. only for the two model years, 1974-75. The differences between the two models were few and generally quite insignificant. In many cases, a revised part number was just a hardware callout; longer screw or larger diameter washer. Other differences involved a change in materials, such as steel from aluminum.

In all cases except one, any RL250 part will fit either model. The exception is that the early '74 models had a 4.16:1 primary gear ratio (75Tx18T) and the later '74 and '75' models had a 4.23:1 ratio (72Tx17T). The gears for the two ratios cannot be mixed.

According to Suzuki, the serial number break between models is as follows:

bullet1974 RL250L - Frame - RL250-10001, Engine - RL250-10001
bullet1975 RL250M - Frame - RL250-18199, Engine - RL250-18223

In all my years of working with the RL250, I have never, ever, seen one with matching frame and engine serial numbers. I have RL250 frame serial number RL250-10026, the 26th RL250 off the line, with its original engine with serial number RL250-10061. So, right from the beginning, the engine and frame serial numbers did not match. My feeling is that the serial numbers are generally off by as much as 250. I've not been able to determine any reason why. Maybe it just wasn't important. I have a 1974 TM400L, though, with matching numbers.

Some differences between models are:

bulletFuel tanks - changed to steel from aluminum sometime in '74
bulletKick starter crank lever - identical except for plating, chrome for '74, silver cadmium for '75.
bulletTank decals - orange with white trim for aluminum tanks, gold with black trim for steel tanks
bulletControl lever perch clamp hardware - Phillips head screw for '74, hex head bolt for '75
bulletRear shock springs - very early '74 not progressive wound
bulletClutch Cover Case - three part numbers listed, two for '74, one for '75 with different quantities and filler plug types
bulletPrimary drive ratio - these are the gears on the right side crankshaft end and the clutch basket.
bulletChain guards - aluminum for '74, steel for late '74 and '75.
bulletLower fork outer tubes - drain screw location; on the bottom early '74, aft facing on late '74 and '75.
bulletRear brake cable - from RL specific cable to the same used on the TM400 and other bikes

It is impossible to distinguish when the more significant changes actually began to appear on new production bikes. Suzuki, like most manufacturers, will use up their old stocks before bringing in the newest part that will not necessarily be coincident with a new model introduction. The '74 model appeared in late winter/early spring of 1974. From an engineering viewpoint, changes were being made even before the first bikes hit the showroom.

Suzuki designers were tasked with the mandate that the bike had to weigh in under 200 lbs. The sales brochures for both the 1974 and 1975 RL250s indicate 199 lbs. even though the photos clearly show the 1974 has an aluminum tank and the 1975 has a steel tank. It is interesting to consider that the aluminum tanks and chain guards may have been incorporated just to make the target weight as they were quickly phased out after production began. Also, interesting, is that the weight did not change with the heavier steel tank and chain guard.

Please ask if you have any questions about part applicability.

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Last modified: 05/26/14