Machining AMS 105" Big Bore Jug Kit for Harley Twin Cam

Описание: This is an older video showing how we bore and hone Harley jugs for our AMS H-Torque Pork Big Bore kits. Depending upon other parameters of the engine, we use either forged pistons, made to our specs by Wiseco, or Hypereutectic KB pistons made to our specs. We also source pistons from CP, and Arias. We start by miking the pistons at their gage line, and recording their diameters. Next we place the jug in our lathe's Accu-true chuck and shave .002" off the gasket deck surface. This ensures the surface is not warped, has the proper Ra/Rz surface finish (so the head gasket will seal perfectly), and is aligned parallel with the jug's base.

Torque plates are installed on each jug. Torque plates simulate the clamping loads placed on the jugs when installed in the engine. These forced actually distort and squeeze the jugs out-of-round by as much as 0.008", creating "lobes" near each head bolt, top and bottom. By using torque plates to simulate this deformed condition, while we bore and hone the jugs, it will ensure the bore is round and true when the engine is in operation. A round/true bore delivers more power, and helps prevent the dreaded "oil puking" experienced by many Harleys built with brand X big bore jug kits. Since this video was made, we have designed a newer production torque plate system ... it does the same job, but lets us clamp the jugs much faster. We'll try to get a new video showing it and our new Sunnen SV 10 Hone Machine posted soon.

We bore the jugs on an air-floating pneumatic self-centering heavy duty boring stand that uses the previously trued gasket surface to "square" the jug to the bore. The self-center, air float feature eliminate operator error, ensuring each jug bore is properly located and "square to the world". Many shops use smaller boring machines, sold for doing smaller motorcycle jugs - we have one too - but when dealing with nearly 4" diameter Harley jugs, our 50+ years of experience has taught us that a much heavier and more rigid machine will deliver greater accuracy. An old rule of thumb in the machine shop industry is heavy rigid machines = greater precision. Since this video was made, we now use an even larger, heavier and more rigid CNC Vertical mill to bore cylinder. This was necessary to keep up with demand for our AMS big bore kits.

While boring the jugs, we take several small cutting passes, to avoid micro fracturing the underlying sleeve's metal. We use CBN inserts which help maintain a nice parallel and round bore. We also monitor the jugs temperature when miking the bore and making any adjustments to the cutter. The heat from boring can bake the jug grow and distort within the torque plates, leading to tool compensation errors and out-of-round rough bores.

Once the jugs are bored to within a few thousandths of an inch from finished size, we move to a Sunnen diamond hone. Honing will remove the machining marks, and leave the proper "cross-hatch" surface finish for quick break-in and oil control. We prefer diamond hone shoes over less expensive vitrified hone "stones", because the diamond hones hold a more precise cylinder shape, and do not heat or distort the jug as much as stones.They also bring the cylinder to finished size, with a +/-0.0001" tolerance. The piston diameter data recorded earlier is now used to ensure that each individual piston is optimally fit to the jug. Most pistons, today, are manufactured with very little variance, and many shops omit this step - however, it only takes a few minutes to include, and it makes sure the pistons / jugs have the proper clearance... so your AMS big bore kit delivers quiet, rock-solid reliable power, without puking oil :-) Since this video was made, we now Diamond hone the jugs on a CNC controlled Sunnen SV-10 Hone Machine, with power-stroking... which allows us to produce more cylinders in less time, while still maintaining top quality precision bores.

After diamond and plateau honing, the jugs are thoroughly washed and rinsed several times with hot water. Then we test the surface finish Ra/Rz. Next we check rings' end gaps. We use a diamond wheel grinder equipped with a dial indicator to precisely set the ring gaps. You'll note in the video that we also gently chamfer the edge of the ring's end. This step is often overlooked by many builders. By chamfering the end's edges, we remove any tiny metal burrs that could damage your pistons and cylinders. Each ring is checked, fit, and and rechecked before being packed up with the piston and jug for shipment.

We offer exchange 105" Big bore kit for 2007 and up Harley Twin Cams, and 96" Big Bore Kit for '99 - '06 Twin Cams. We'll also custom bore and hone your original jugs if desired. Our shop uses the same precise process when boring Shovel, Evo,and Sportster jugs as well. For more info about our AMS Big Bore Kits or having your Harley jugs bored and honed, give us a call at 1-800-210-8675.