After reading a few posts on internet message boards, and talking to several fellow pilots, I seem to hear the same thing: "It's too hard to replace a clutch liner," or "I've tried, but can't get it correct, so I just replace the complete clutch bell." Well, this is okay, but expensive. Hopefully after reading this you'll be changing your own just like the pros.
There are several reasons clutch liners go out, but here are the 3 most common:
1) The hot start.
If not stopped very quickly, this is a sure clutch killer.
2) A crash with idle up on.
Come on, we've all done this at least once.
3) Worn out; great!
It takes a considerable amount of normal flying to wear out a clutch liner, and if this is the case, you're doing well!
NEW CLUTCH INSTALL: STEP-BY-STEP
1. Inspection
So there you sit with a box full of perfectly good clutch bells, with little or no liner. The first thing we want to do is clean and inspect the clutch bell, as there is no sense in putting a new liner in a bad clutch bell. Clean it thoroughly with alcohol, and wipe it dry. Now place the clutch inside it, and look around the complete circumference to see if the gap is the same all the way around. It doesn't have to be perfect, but any more than about .010" out of round is going to give you a less then perfect clutch engagement. If the old liner is still inside, and is in really bad shape, you will probably need to remove it before evaluating the bell.
2. Out With the Old
To remove the old liner and glue--and this is important--you must get the bell back down to bare metal. First, I like to protect the bearing, so if it's in place and in good condition I choose to leave it there and simply place a small piece of duct tape over it. Next, if all or most of the liner and glue are gone, I simply take coarse sand paper (I use 80 grit) and sand out any remaining liner and glue. If there is a considerable amount of material to remove I have found the following to work very well.
Gently chuck the pinion gear into a variable speed drill (I use my cordless), turn it on very slowly, and check that the bell runs true. If not, simply loosen it, rotate it slightly and try again. I have always been able to get it to run true after a few tries. DO NOT OVER TIGHTEN or you will damage your pinion. Now while slowly turning the clutch bell, sand the inside with the coarse sand paper. This usually only takes a few minutes, and will leave behind a clean and roughened surface to glue your new liner to.
NOTE: Never try to remove the liner with anything other than sand paper while spinning the bell in a drill.
3. In With the New
Start by test fitting your new liner. Some brands come pre-cut to the correct length, and some will need to be trimmed. I like to see a tiny gap, maybe 1 /32" or so. Now take your clutch and apply several wraps of electrical tape around it (6 to 8 should be fine), being careful to stay flush or close to flush on the side that goes into the bell first. On most clutches this will leave the tape hanging over the opposite side, and this is fine. Take a razor knife and cut a line through all the layers of the tape, right down to the clutch.
4. Easy Does It!
With the liner just lying in the bell, gently push the clutch into the bell, which should press the liner against the bell. DO NOT FORCE IT! It should go with just a light push. If it does not, simply go to the line you cut through the tape, remove one layer and try again. Keep doing this until you get a light push that is holding the liner to the bell without undue pressure being needed to insert the clutch. If on your first try it was too loose, remove all of the tape and re-wrap it using more layers. This may also indicate that either your clutch or clutch bell is excessively worn, and may need replacement.
5. Sticky Situation
We want to glue the liner into the bell. For this I use slow, medium thick CA glue. I brush it on the inner surface of the bell with one of those cheap throw away brushes, this way I am sure to get 100% coverage with a thin coat of CA. Now carefully put the liner in and push it against the glue. Next, push your clutch with the tape back in, and it should hold the liner in perfect position. Give it a good look--this is why I use SLOW CA--and adjust if necessary. Once you get it in place correctly, set it aside overnight.
6. Check Your work
Okay, it has sat overnight, now you want to see your work. Gently remove the clutch, and remove the remaining tape from it. Now wash the clutch with alcohol to be sure there is no sticky tape residue left on it. Place the clutch back into the bell and check clearance; the recommended clearance is slightly different for different models. However, I have found that if you can put 1 to 3 pieces of regular paper between the clutch and bell, it will work fine.
All Finshed!
That's it, you're done, and usually for less than 1/10 the price of a new clutch bell. After a few tries this entire procedure takes about 30 minutes, and you'll be doing it like an old pro.
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