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PENTON / KTM / SACHS / DKW motorcycles
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Working on Motors / Professional Services / Tech Tips
General Rules for Working on Motors:
If you are planning on repairing a motor, clean it thoroughly first before splitting any of the cases! This prevents dirt and crud from getting into the motor and make re-assembly faster and easier.
To simplify ordering the parts needed in rebuilding motors, I have gasket kits available. Each kit contains all of the gaskets, seals, o-rings, fiber washers, and metal lock washers needed to rebuild the following motors:
Sachs “A” motors / Sachs “B” motors
KTM 175 Black motors (72-73) / KTM 175 Silver motors
KTM 250 motors / KTM 400 motors
I also have a limited number of original gasket kits for the 1979 - 1982 KTM motors.
NOTE: The gasket kits do not have an ignition case gasket. Gaskets should not be used to prevent condensation build up in the ignition area. If you are planning to use your bike for submarine use, the ignition case can be sealed up with silicone, but it must be vented! A hole can be drilled into the top of the ignition case and a plastic elbow (part no. 51-30-022-0000) can be screwed in to allow a plastic vent line to be inserted and run up under the seat.
It is very important that moisture be kept away from the motors - especially the KTM’s. They are made of magnesium which will corrode (turn into a white powder) if kept wet or damp for long periods of time. If you wash your motor after riding it (a good habit especially if the motor is coated with wet mud), remove the ignition cover after washing, and run the motor to evaporate any moisture on the motor.
Read the owners manual before pulling the motor out of the frame to familiarize the proper way to remove and disassemble it. This will help prevent damage to any components.
Take your time when disassembling a motor. The center cases should come apart with a few gentle taps of a wood or plastic mallet. Do not force cases apart. If they are binding, check for a screw that may not have been removed.
When reassembling gaskets, do not use any form of gasket cement! The Sachs and KTM motors are precision built machines. Soak the case gasket in warm water before installing them. Use a thin film of grease on the case halves. The grease holds the gaskets in place and helps to seal them. Soaking the gaskets make them pliable and easily fit the contours of the motor.
A quick way to check for a worn or damaged crank bearing without tearing apart the motor - grab the flywheel and see if there is any noticeable up and down movement. There should be absolutely none. Any noticeable play could indicate damage to the Motoplat ignition if you are checking out a motor that is not in running condition. (Motoplat units have a very close tolerance between the flywheel and the lower unit).
When re-building a motor that looks like it has never been apart - replace the crank bearings whether it needs it or not.
When you replace the crank bearings, do not use a single piece bearing. Use the 3-piece bearings. They are more money, but they enable the cases to be opened and closed without damaging them. The 3-piece bearings are carried in stock.
Do not operate any 2-stroke motor without an air filter. Doing so will cause damage
to the crank bearings, cylinder walls, and rod bearings. Make sure that the air filte is kept clean and oiled after every use of your bike. I recommend the new generation of oils such as "No-Toil" which are alcohol based, dry quick and super tacky, and use a special soap powder when mixed with water clean the filter quickly, easily, and ecologically.
To drain oil from Sachs motors, do not use the drain plugs - remove the clutch case cover.
With the age of aluminum covers, when attempting to remove the drain plugs, the
threads on the covers will come out with the drain plug. If this happens to you, it can be
repaired by buying a larger size drain plug, and tapping a large size hole in the case.
The rule “if it isn't broke – don't fix it” applies to the Penton/ KTM motorcycles, however since these bikes are 25+ years old, the following items must be replaced during restoration, and checked on a regular basis if the bike is used for competition use: