What is the clutch liner clearance on an XCell 60
XCell specifies .007 to .008.
The clutch liner on an XCell is oversized and once installed the clutch will not fit into the clutch bell. XCell states that they will install a new liner and size it for the price of the liner. If you choose to perform the task yourself you should have a lathe available for turning the liner to the proper clearance.

What is causing my vibration or skid breakage
Skid mount breakage: Any engine vibration in an X-Cell 60 will show up in the front left skid. Miniature has known of this problem for years, but I guess it's just inherent to their design. The only item that Miniature ever stated was to ensure that the skid attachment holes were larger than the bolts and that the skids slid on the heli without any binding (I.e. make sure the holes in the skids are oversized for the bolts which attach them to the frames).

If you watch an X-Cell in hover, which has an engine vibration problem, you will see that the front left skid is a blur. The rear left and right side will be clearly visible. This is a sure sign that you have an engine vibration problem.

Fin vibration: A second sign would be vibration in the fins. Although this can also be caused by tail drive problems, it is a sure sign that you need to fix something. Some fin vibration will normally occur during spool-up but should completely disappear at hover speed.

If it is a high speed engine vibration then usually both the vertical and horizontal tail fins will be vibrating. Most people notice the vertical but if you look again you will probably see the horizontal is also vibrating. Altering head speed may increase or decrease the vibration but usually will not make it go away. You still need to find the reason.

The most common problem associated with engine vibration is the fan hub. If you are using a metal fan, they are notorious for being out of balance. All metal fans should be balanced prior to use. An airplane prop balancer works well for this. Use the engine mounting collets to center the fan on the balancer shaft. The plastic fan seldom seems to have a balance problem but it's worth checking anyway. Fan hub run out is also a known problem. With the fan mounted on the engine, the run out of the hub, at the point furthest from the engine, should be less than .001. See How do I adjust the run out of a fan hub? Below.

A bad clutch bearing or start shaft block bearing will also show up as engine vibration. The X-Cell start shaft is hardened and will not show wear from a bad bearing unless it has been there for a while. Inspect the bearings, and look for any discoloration on the shaft where it passes through a bearing.

Clutch alignment will cause a vibration problem as well as excessive wear on the drive parts. X-Cell provides a clutch spacer which is inserted between the hub and clutch to assist in alignment when mounting the engine. The hub is held compressed against the clutch to align the unit while the engine and start block bolts are tightened. One problem is if the engine shaft extends too far, it will bottom against the clutch ball preventing you from fully seating the clutch into the fan. This will also cause excessive pressure upward against the clutch and start shaft bearing. Early bearing failure is the result. To check this install the clutch on the engine with the rubber shock inserts removed. The clutch should slide down completely against the hub. If it will not then it is probably hitting the end of the engine shaft before seating. This is cured by either cutting a small amount off the end of the shaft or using a thicker spacer under the hub where it sits on the engine.

Check for wear on the delrin ball or the rubber shock inserts in the fan hub, An engine caused vibration will cause accelerated wear on these parts.

Aside from engine/drive problems, the tail boom and assembly is you next likely culprit.

Check your tail boom support(s). They must be tight with no play.

If you have a wire drive, I suggest that the tube supports not be evenly spaced as this may tune an oscillation. If you have a pipe drive then verify that the bearing and bearing holder is good. I have seen bearing holders come loose on the shaft and wear. (Yes even on the factory installed.)

One hard to set up item is the centering of the tail drive coupler in the tail boom support half shells. If you remove your tail boom and look into the hole you may see that the drive coupler is not centered in the hole. Quite often in setting up the gear lash the coupler is left offset in the tail boom. I center the coupler and align it horizontally and then adjust the gear lash with the bottom shaft collet.

If you are running one of the dampened tail hubs, the one with the rubber insert around the shaft, then make sure the rubber is good. If the rubber is cut to the shaft under the hub then you probably have a tail hub/blade problem.

If you have the dampened tail blade hub, then check that the blade axles are not bent. This hub is soft steel and bends easily. Remove the hub and tail blade grips. Place the hub against a flat surface and measure the distance from the surface to the end of the hubs axle, flip the hub over and measure from the other side. Due to their softness these hubs can be bent in normal handling, you don't need a crash. (They also can be straightened easily, but I usually do this in a lathe with a dial indicator.)

Finally, make sure you tail shaft is not bent. This should not occur in normal handling as the shaft is hardened.

How do I adjust the run out of a fan hub?
The following procedure is based on a procedure written by Ben Minor (RunRyder user Dr.Ben)

After years of hit or miss dialing of fans, Ben stated that he had finally came up with a process to get the job done well. Using this technique, He states that He consistently achieve a fan runout of under 1/2 thousand. Ben says that He won't run anything over 1/2 thousand. Ben further states, make no mistake, a model with a fan runout below 2 thousands will likely show little perceptible vibration and certainly shouldn't crack side frames. however, a model with a fan running with near zero runout has a special, sweet sound, and the bearing and other component life on the drivetrain are exceptional. (I myself shoot for a runout of .001 or less.)

Setup: I use a vise and a magnetic dial indicator base. A dial indicator with a precision of .0001 is best, however an indicator reading in steps of .001 will work. Prepare the engine by removing the glow plug and the backplate. Leave or mount the engine in the motor mount to prevent damage when clamping it in the vise. The engine should be mounted vertically into the jaws of the vise (crankshaft facing up) with the jaws against the side of the motor mount. Do not over tighten the vise. You need only enough pressure to firmly grip the engine. We will not be applying any heavy force to the unit. Now cut a spacer which will reach from the vise throat to the back of the crankshaft when installed in the vise. This may easily be made of a piece of ½" dowel. The dowel is placed between the back of the crankshaft and the throat of the vise to absorb all downward pressure against the end of the fan hub. (Ben also removes the piston and sleeve during this process but states that he does not force that step on people) I mount the dial indicator on the anvil of the vise and adjust the positioning so that it contacts the fan hub at the topmost position. This is the smooth portion of the fan hub above the fan and just below the top face of the hub.

Lightly oil the collects, and assemble the fan on the motor (I use anti-seize lubricant). Tighten the nut until the assembly just starts to draw down. Don't crank down on the nut. Now dial the fan and if the fan is out more than 1 thousandth, gently tap the fan's face with a plastic hammer. The tap should be down, against the hubs face, at the point reading closest to the crankshaft (the point which highest numeric reading on the dial indicator). I actually have a piece of flat aluminum with a thin piece of card glued on to it that I use to protect the fan face from dings. You don't have to tap hard at all to get the fan to dial true.

When you've got the fan back to within 1 thousandth or less, tighten the nut a little more. Redial and retap to retrue/align if needed. Never continue to tighten until you've gotten the rounout to less than .001. As the nut gets tighter, I generally work harder to get to 1/2 thou or below. You might have to tap more than once. You never have to hit hard. The whole reason for tapping as you go is to keep the fan straight on the collets as the assembly tightens down. When the assembly really starts to snug up, make final tap adjustments before completely locking the nut. Almost without exception, if I've reduced the fan runout to 3/4 of a thousandth, or less, just before the final torque, the runout either holds stable or actually improves to drop to below 1/2 thousandths.