Iron Sportster bill of material

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Rear motor mount

Comes in steel or cracked versions.

There are frequent flashes of sheer brilliance in the design of the 1952 K-model and its sibling, the over-head valve Sportster.

But when you get to the rear motor mount system, you have to think "what where they smoking?"

The forces on the engine back here are primarily chain tension between the transmission sprocket and the rear wheel.

But the rear motor mount connects to the left case half, not the right one, where the forces are applied. Worse yet, it is captivated, you can only remove it by splitting the cases or removing the three studs it mounts with.

Sportster-Engine-Case-Cases_Rear-motor-mount-location

The aftermarket makes stronger mounts that are relieved to allow removal without splitting the cases or pulling the three studs.

The early mounts were made of cast steel. They rarely if ever crack. In the 1960s the engineers made the mount out of aluminum using what appears to be the same mold. These parts crack in the top flange near the bolt holes.

The designers also made a running change around 1962 where they used steel inserts where the bottom two frame attachment bolts go.

16201-52 1952-1961E all The original part had a small hole where the kickstarter shaft passes through. It captivates the shaft, so you have to split the cases to remove it.

Some time in the late 50's the engineers made the kickstarter shaft hole much bigger, see below. Here is the lower pad where the frame bolts attach. Since the entire mount is steel, the holes are threaded and resist stripping. The bolts are 3/8-24 UNF fine thread, with the 9/16 head. Length depends on whether there is rear foot pegs or center stand mounted.

Despite its shortcomings, at least this steel part has dignity. The part locates the rear of the engine vertically. Side-to-side location is done by the bolts..

Here is a comparison of the later steel mount with the bigger hole for the kickshaft to pass through (right). Although the casting is different, there is no call-out for this part in the parts book.

The parts books do not call this part out as a separate number. The folks over at Harley K Model hypothesize the part may have had an "R" suffix and use in KR race bikes. It is not certain that this part was used on production bikes, but if so, it would have been the 1957 Sportster and perhaps the very late K-models.

16201-58

E61-E62 all

The Harley K Model site also details the existence of this part, identical to the -58A below, only no steel inserts for the lower frame mounting bolts.

16201-58A

L62-66 all 67-69 XLCH

This part is documented in the parts books. It looks to be the same casting mold as the large-hole steel part, with the addition of the steel inserts where the lower frame bolts attach.

This part starts the legacy and tradition of cracking. It was a weight reduction for the Sportster models.

The cracks form in this flange, probably from dropping the bike or loose top and front mounts.

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16203-67

67-81 XLH 70-81 XLCH

This part is similar to the -58A only the top flange only accommodates two bolts. It is used with electric start bikes starting in 1967, and all bikes from 1970 to 1981.

The engine cases were different for kick and electric start bikes between 1967 and 1969. The kick-start cases had the four bolt holes on the top for the -58A mount. The earlier steel mounts will also fit this case.

You can also cut the front of the top flange off the steel motor mount and use it in place of this part.

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The frame bolts to this flange. You can see the threaded steel insert on the backside for those two bolts.

This flange is the one that cracks. The cracks can be on either side. Sometimes the crack is near the bottom (case) bolt holes. Other times the crack is near the frame bolt holes. There will be cracks, so inspect carefully. TIG welding will repair the crack if you cannot find a large-hole steel mount to replace the part with.

This bottom flange locates the engine both fore and aft and vertically. Tightening the top frame bolts should rotate the engine so that the front and top motor mount holes line up with the frame. The threaded steel insert is a press-fit. The insert is called out separately (16202-62) in the parts book, so you can replace the insert if it is stripped out.

16203-82A 82-84 all In 1982 the engineers adopted the superior Nippondenso starting system.

The engineers redesigned the 1982 case "hump" to mount that starter motor. They also removed any provision for a kickstarter. Therefore there was no need to have a hole in the rear motor mount for clearing the kickstarter shaft.

Sportster-Engine-Case-Cases-16203-82A_Rear-motor-mount-rt3-4

The superior strength and design of this part are admirable. It is still rather sad to see a Harley engine without a kickstarter. Its not just a Bronson-like cool thing. You can start a kickstarter bike when the battery is nearly dead.

Kickstarters are also nice when you service the bike. It provides a handy way to turn the motor over when you are looking for a flywheel timing mark, or pulling a replacement rear chain around the front sprocket.

A summary table for this part:

Part	Descript	Used on	Note
16201-52	Rear motor mount	1952-E62 all	Steel, both large-hole and small-hole versions.
16201-58A	Rear motor mount	L1962-66 all 67-69 XLCH	Same shape as -52 but aluminum material.
16203-67	Rear motor mount	1967-69 XLH 1970-81 all	Top flange only has two bolt holes for electric start case
16203-82A	Rear motor mount	1982-84 all	No hole for kick-starter shaft.

Rear motor mount

16201-52

16201-58

16201-58A

16203-67

16203-82A

Sub-assemblies