T-Rex 600N (belt version) last updated 7-28-2007

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Fan - it looks assembled but it is not. The bolts holding the plastic fins to the hub need to have blue loctite put on them and be tightened. If you have a governor/limiter then install the magnets in the fan. Make sure one is the opposite direction of the other. And if you have a high point balancer then check the fan.

Fan hub install - remove the clutch so you can put the crank shaft nut on. Installing the fan hub on the crankshaft proved to be difficult. I measured the crankshaft and the fan hub to both be 0.375" so it seemed like it should fit but I only got it to go on a short distance then it was stuck! A good tight fit is nice but this was a bit too much... After a little more investigating I figured out the problem was the small hole of the hub as you can see in the picture on the left. The fan had an ID of 0.249". The section just below the thread on the crankshaft however was 0.003" larger. So I used a dremel with a grinding bit to grind the inside surface of this hole. This fit pefectly, the hub would slide on without a lot of force. If you cannot push it on with your hand then the hole is still too small. When you get the fit good then make sure you put the thin washer on the crankshaft (the washer that came with the engine). Place the fan hub on then put blue loctite on the crankshaft nut that came with the engine and install it. Then use M3x12mm bolts on the side of the hub to 'clamp' it to the crankshaft.

Install clutch - use the M4x8mm bolts to attach the clutch to the fan hub. If you have a dial point indicator like shown in the picture above then check the runout. I always aim for less then 0.001". If you get more then this then loosen the clutch bolts and try to move the clutch to center it up. Also try taking the clutch off and turning it around 180 degrees.

Next before you put the engine in, put the fan shroud on the engine. The shroud will fit loose on the engine. It does not bolt to the engine but you have to put it on now because you cannot add it afterwards with the engine in the frames.

Now remove the high speed needle from the engine and slide the engine with fan shroud up through the bottom of the frames. Use four M3x14mm bolts with M3 washers to bolt the engine to the engine mounts. Make sure you put some blue loctite on the threads. With the bolts just tight enough that you can still move the engine a small amount, test the alignment. To test it you turn the top of the start shaft. Try twisting the engine all directions to find the position that lets you turn the start coupler with the least amount of resistance. Once you find this position then tighten the four bolts that go into the engine mounting blocks. And re-install the main needle for the engine.

The next part is the fan shroud, Use the starter shaft from your starter motor to turn the engine and confirm that the fan is not hitting the shroud. Shift the shroud so that it does not touch the fan then use four T3x10mm button head bolts to secure the shroud to the frames. There are two per side (circled in red in the picture above).

And the final part to this section is adding the radio tray. Use four (two per side) T3x10mm button head screws with the specialy washers. Be careful not to over tighten the screws going into the fan shroud. If you do strip them then put some CA on the tip of the screw and that should hold it

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