Question about 1979 Harley Davidson XLH 1000 Sportster
Rebuilding the top end on your Ironhead is not really that difficult to do. You start by taking the tank off the frame, then the carb and intake manifold off. With those off, take the four bolts out of each head and remove the heads. With the heads off, take the four bolts out off of the studs to remove the cylinders from the engine cases. One word of caution. When you remove the cylinders, have the piston up high enough in the cylinder so that you can lift the cylinders and stuff shop towels or something into the case before completely removing the cylinder. This will keep bits of carbon, broken rings, or whatever from falling into the case.
Now, that you've got it torn down, no need in doing all this work and not refreshing the engine. I'd have the cylinders checked to see if they needed boring. If not, I'd still put a new set of rings in the engine. They don't cost that much. Have the machine shop break the glaze in your cylinders if you don't have a flexhone. If you have a lot of miles on the bike, a valve job would be in order as well. Clean all the old gaskets from everything. If you have a valve job done on the heads or you've got oil leaks at the rocker boxes, remove them and replace the gaskets. This is a good time to check the rocker arms and rocker arm bushings. Replace them if needed.
Once everything is ready, put the rocker boxes back on the heads. Use good gaskets and a good sealer. Put locktite on the bolts so that they don't come loose. Once you get the heads back on the engine, you probably won't be able to to get to the bolts. Install the base gasket on the cases. Put the new rings on the piston making sure you get the right ring in the right groove and you put them in with the right side up. Refer to the instructions that comes with the rings to determine which side of each ring should be installed in the up position. Oil the rings thoroughly and space the end gaps around the piston at 60° or so apart from each other, do not align the ring end gaps. Carefully slide the cylinder down over the piston and rings. Use your fingers to compress the rings so that the cylinder slides down over the rings easily. Do not use force or you may break a ring. Torque the cylinder base nuts to 35-40 foot pounds. Now, install the other cylinder using the same techniques.
Next comes the heads. Choose the head gasket you are going to use. They come in two thicknesses. I prefer the thicker gasket. It will cost you a bit of compression but they seal better. Spray each side of the copper gasket with CopperCoat spray adhesive and position the gasket so that the oil drain hole is properly aligned. Carefully set the head down on the cylinder without disturbing the head gasket. Install the four head bolts but only snug one of them down. Then install the other head the same way.
Now, the reason you only snugged one head bolt down was you must align the intake ports with the intake manifold. Hold the intake manifold in between the intake ports of the heads. Notice the gap at the intake ports. If it is wider or narrower at the front than it is at the back, you must "rotate" the heads until the gap is even. Once this is done, you can tighten the head bolts. Tighten them in a criss cross pattern to a torque of 60-70 foot pounds.
Now you can install and adjust your pushrods. Use new O-rings on the pushrod tubes. Bring the front piston to Top Dead Center. Use a common drinking straw in the spark plug hole to determine when the piston is at it's highest point. Do NOT use anything that is hard or that will break. You could damage the piston or break the tester off in the cylinder making you have to pull the head off again. With the piston at top center, adjust each pushrod longer until you can't turn it with you fingers, then back off until you can just turn it freely. Lock the locknut down tightly. It's better to leave the pushrod a bit loose than a too tight. Do the same with the other pushrod. Put the pushrod tube into it's proper position. Now, bring the rear piston to top center and install the pushrods and tubes on that cylinder. It makes no difference which pushrod goes in what position as they are all the same length on the Sportster.
Now you can install the carb. Use new "rubber bands" on the intake clamps. Make sure you position the intake so that the carb is level. Position the clamps and "rubber bands" so that you won't have any vacuum leaks and tighten them down. Once the carb is installed on the intake, check the throttle for proper operation. You don't want to start your bike only to find out that the throttle is wide open. Install the fuel tank and you should be ready to go.
Posted on May 31, 2010
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Posted on Jan 02, 2017
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