Removing Rotor from Onan Engines

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So you have the Onan engine 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, that a year or two ago sold for over $125.00 I recall paying about $20.00 10 years ago.Option # 1 Buy the kit from a Lincoln dealer. This is the best way to go if possible.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. 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.Now you need to get another thru bolt identical to the original, Lincoln used several sizes over the years. Cut it about two inches shorter from the head end and then cut a slot in it that a screwdriver will fit in so you can thread it into the crank all the way then back one turn. Failure to do this will 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.Good luck! Attached ImagesMiller LegendMiller XMT 200Miller HF 251DMiller Spoolmatic 30AMillerTrailBlazer 250GLincoln LN 25Lincoln G9 ProLincWelder 225Lincoln Ranger 9Lincoln Ranger 275TJhttp://onanparts.com
Reply:Nice tool.  The last one I took off, I used a 5 lb dead blow plastic hammer.DavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Originally Posted by David RNice tool.  The last one I took off, I used a 5 lb dead blow plastic hammer.David
Reply:hit it with a rock till it smokes and seal it with a rock
Reply:Originally Posted by boilermakerhit it with a rock till it smokes and seal it with a rock
Reply:I have not done this but it seems to me if the through rod was loosened a few turns and a couple of swats with a BFH should loosen the crankshaft in the rotar.
Reply:Another thaught, could a new engine shaft be machined except a longer straight where the counter weinght is and then you would have about 3" of shaft to work another motor.
Reply:HI  I worked on the ranger 10000 line we would remove the rotor by backing up the through bolt 4 to5 turns and hit it wit hammer