M6 BT-17-M8 Frequently Asked Questions << M6 BT07 Is there any initial break-in time? Yes. Due to the links in the primary chain gliding over our nylon shoe, you will notice 3 groves slightly wearing on the shoe until the chain 'seats' itself and the rollers come in contact with the top of the shoe. This is normal and usually happens within 400-500 miles. We suggest rechecking the spring compression measurement once this has occured. You may or may not need to add a shim. My M6 came with a lot of different SHIMS, what do I use? Your M6 box should have 2 shims in it. The shims are shaped like a capital "U" one is thin (0.063") and the other is thick (0.125"), you only use the shim or shims necessary to acheive the 3/8" measurement. Keep in mind, you may not need any shims at all. Depending on your primary chain condition, the M6 may be installed without any shims. Is there a specifc primary fluid that needs to be used with the M6 and it's components? No. The M6 does not require any special pirmary fluid. The "shoe" material is designed to be used with any "normal" primary fluid. Not only do we follow Harley with their suggested primary fluid, but we also recommend popular after market brands and have had no instances of brittlness or premature wear when other primary fluids are used. "The primary fluid you are currently running will work fine with the M6". The M6 appears to 'hang out' over the edge of the primary case. Is that normal? In some cases, the M6 actually extends out past the primary case. This is normal. Do the SPRINGS ever wear out of get weak? What if I break a spring? Our SPRINGS are custom made for us. You cannot buy them in a hardware store. It is unusual that we ever have to replace springs but they can always be purchased directly from us. How long will the M6 last? One of our first installations (over 13 years ago) now is approaching 600,000 miles on the M6. He has installed 3 primary chains during that time, but figures when you can get over 100,000 miles on a chain you are doing real darn good. AND, he's still on his first SHOE. What is the measurement for the SPRING COMPRESSION area? 3/8" from the bottom of the SHOE to the top of the SHIM pack. If you are installing the M6 on a stroker or in conjunction with a Fisher Damper, you may need additional spring pressure, so we recommend the distance be set a little tighter. How many SHIMS do I use? Depending on the amount of miles on your primary chain, the number of shims will vary. What is important is to achieve the 3/8" measurement in the spring compression area. Start with one shim, then measure the area between the BOTTOM of the nylon shoe and the TOP of the shim. If you have a 3/8" measurement, you are done. If not, add another shim and measure again. The more miles on your primary chain, the more chain "stretch" you may have had. Keep in mind it will depend also on how those miles were put on. Once you are certain you have reached the 3/8 " measurement you will need to keep your extra shims for future use. As you have chain "break-in" time or "stretch" you will need to add additional shims to maintain the 3/8" clearance. How long can I expect the SHOE to last? It is not unusual to see well over 100K miles on an M6 shoe. As long as the correct lubricate is used in the primary case and the M6 is checked for wear every 20,000 miles, you should expect to have a long shoe life. Replacement SHOES can always be purchased directly from us. You do NOT need to purchase a 'complete' M6. What if I loose my extra SHIMS? You can always purchase any of the pieces of the M6 directly from us. When will I know I need a new PRIMARY CHAIN? Over the years you will continue to add additional shims as your chain stretches. When you get to the point that you need more than 2 SHIMS, it is an indication that your primary chain is worn and should be replaced. Once you replace your chain, back off the M6 and start over with a minimal amount of SHIMS to achieve the 3/8" measurement. My bike is making a WHIRLING sound. What is it? The M6 does not have any 'hooks' into your system. We are merely providing a surface for the chain to glide over. In some cases, we have had a 'whirling' sound reported to us. If the M6 is installed properly and the 3/8" measurement is achieved this sound is simply the chain gliding over this shoe. It will generally subside within the first 200-300 miles. Most installations don't hear this at all. If you should, don't be alarmed. It is not causing any pre-mature wear on your chain or our shoe. How often should I check the M6? Check the unit for wear every 20,000 miles...always keep clean oil. << M6 BT17