KTM 175 Cranks

What's the Difference?

By Alan Buehner and “Chicago” Jerry Grakauskas
Photos by “Chicago” Jerry Grakauskas

Just when you think that you know it all, something comes up to make you shake your head. I always knew that there were 2 types of 175 cranks. One for the “black” engines and one for the “silver” engines. “Chicago” Jerry informed me a couple of months ago that he has encountered a third type of 175 crank which is where these photos came from and why this article was written. He is quite certain that the newly discovered crank size came from the factory that way. It was not a conglomeration of mixed parts. He has three of them that are identical.

Now there is a possibility that this third type came about because someone screwed up the mag side threads and exchanged the crank half, but, anyone that is going to be dealing with rebuilding a Jackpiner engine needs to know what is out there and be ready to expect some problems. This article should help you deal with it.

Photo A. Black engine crank that uses 2 M-20 crank bearings.
Both shafts measure 20mm in diameter. Photo shows the inner races of the crank bearings in place.
Photo B. Silver engine crank that uses 1 M-20 & 1 L-25 crank bearings. The left shaft measures 25mm in diameter, the right shaft measures 20mm in diameter. Note that the right shaft is straight from the crank journal towards the end before it reduces in size.
Photo C. Silver engine crank that uses L-25 crank bearings
Both shafts measure 25mm in diameter.
Note that the right shaft is straight and then tapers down.

The first photo (A) shows the crank from a 1972 “Black” engine with the same small diameter shaft on both sides requiring two m-20 (small) three piece bearings that measure 20mm I.D. X 52mm O.D.
Both shafts measure 20mm in diameter.
The corresponding small seals are as follows:
The ignition side measures 20 x 30 x 7 mm .
The part number is #0760-203-070.

The primary side measures 20 x 35 x 10 mm.
The part number is #0760-203-510.

The second photo (B) shows a crank from a “silver” engine with the magneto side (left side in photo) being large and requiring a L-25 bearing but it still has a smaller clutch side (right side in photo) half requiring a M-20 bearing.
The corresponding seals are as follows:
the ignition side measures 25 x 35 x 7 mm
The part number is #0760-253-570.

The primary side measures 20 x 35 x 10 mm.
The part number is #0760-203-510.
NOTE: If you have one of these cranks, make sure that you measure the mag seal after removing it.

The third photo (C) shows the crank with the same larger diameter shaft on both sides, requiring two L-25 three piece bearings that measure 25mm I.D. X 52mm O.D.
Both shafts measure 25mm in diameter.
The corresponding seals are as follows:
the ignition side measures 25 x 35 x 7 mm
the primary side measures 25 x 35 x 7 mm.
The part number for both is #0760-253-570.

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