Untitled Document

Gone Fishin

Removing Lincoln Rotors

So you have the Onan engine & rotor removed from your Lincoln welder but how do you get that rotor separated from the crankshaft? It's on there tight and will not let go! You got the rotor to motor thru bolt out also but the rotor is STUCK tight to the crank.

Why? Because the crank is tapered and when the rotor is installed the thru bolt draws the crank and rotor together for a really nice tight fit that will not slip under load and at 3700 RPM

There is a right way, a wrong way and a cheap work around to solve the problem.
The wrong way will damage a very expensive rotor.

Lincoln makes a "rotor pulling kit" part number S20788. Current list price is $150.00 The kit includes the puller pictured below along with the three common sizes of modified rotor thru bolts they have used over the years.

Option # 1 Buy the kit from a Lincoln dealer. This is the best way to go.

Option # 2 Make your own.

The rotor has a Left Hand ACME style internal thread at the support bearing end and you will not find a bolt to fit it at any typical hardware store or nut & bolt house.

The ACME thread is very close to a 5/8 X 11 NC size. The work around is to get a 5/8 X 11 LH NC "left hand" tap and re-thread the rotor at least two inches. A piece of 5/8 X 11 LH all thread about three inches long and two nuts to go with it, lock the two nuts together at one end and you have a cheap rotor pulling tool.

The Hanson tap part # is 2152 & the H.W. co. part # is 54062. 5/8 X 11 Left hand nuts & allthread are easier to find than any left hand bolts.

Now you need to get another thru bolt identical to the original in length or longer. Lincoln used several sizes over the years. Cut it about 1 3/4 inches shorter than your original from the head end and then cut a slot in it that a screwdriver will fit in so you can thread it through the rotor into the crank all the way then back one turn. Failure to do this may damage the internal crankshaft threads!

Install the removal tool until it contacts the thru bolt and get it as tight as you can. Very carefully smack it with a big sledge hammer once or twice or three times etc. If the rotor does not "pop" off then tighten the tool a little and hit it again, repeat until it comes apart.

You need to be certain that the removal tool is actually contacting the modified thru bolt.

Make sure to place a block of wood under the rotor to support it and prevent damage when it lets go. I use a toothless three point style vise grip clamped to the crank to keep it from turning while tightening the removal tool.

On older Lincoln rotors with no internal thread at all this work around is the only way to get it done. Also works on Lincolns with B & S engines. Always replace the support bearing before putting it all back together. 6205RS double sealed type. The early rotors used a double shield type bearing that won't last as long as a double seal style.

Put some Loktite on the thru bolt when you are ready to put the rotor back on the crank.


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