Folks, I got some very good responses from the UL group list for the post below, due to that decided maybe I should post it to this list with all the comments. You not done installing your Rotax engine until you safety wire the spring that hold the flex ball joints together and squirt a good stripe of automotive Red high temp (RTV) silicone gasket sealer down the length of the spring. The safety wire must pass thru the center of the spring and at least one of the loop (both loops preferred to hold things together) on the exhaust system. (Received a reply that you can use a more ascetic pleasing normal temp clear, claimed the springs don't get hot but mine look like they get hot.) The reason for the safety wire is to keep the spring out of the prop should it break or come unhooked. The RTV keeps the spring from vibrating which contributes to their breaking. Using pliers to install the springs causes nicks which contributes to their breaking later. Use of a spring puller is suggested. It is tool that looks some thing like a screw driver which has a hook on the blade end used to grab the hook end of the spring when installing or unhooking the spring. (They may be straight or L shape - the L gives you more leverage.) The tool could be fabricated our of some metal banding like they use to band crates for shipping or a flat blade screw driver by putting a notch in the side of the flat part. Depending upon kit manufacturer or engine supplier, the spring fastening loops may not be installed on the exhaust system or may have to be moved. As an alterative there now id a available a kit for fastening ball joints together that has some advantages over the use of spring but may eliminate need to weld loops on the exhaust pipes. Ask you kit manufacturer if any modifications are required to standard Rotax exhaust system. You may want to have your muffler coated to keep it from rusting. May people try high temp paints and so forth only to learn it doesn't work and usually bite the bullet later and have it done. We can recommend High Performance Coatings - they have several locations, we have experience with there OK outlet. We suggest the silver or aluminum color. Our 3 -year old FireFly still looks like new. Contact them at the URL below: When you request a quote tell them the number of pieces - Rotax exhaust system - don't say airplane or the cost may go up. State how you want it returned and what priority or they may send it air. http://www.hpcoatings.com/ jerryb Below are additional feedback received. A hockey skates-lace puller works really well for pulling the spring. Made my tool out of a pull handle for the emergency brake in the car. Cut it out of a junker. Leave it about 10" long. Bend a tight crook on the end of the wire. Done, cheap and simple. The molded plastic handle makes a great handle for pulling. I use a short piece of safety wire tied in a four inch end to end loop. The flexibility of the safety wire allows me to install and un-install springs with ease. For a handle, I use a medium size phillips screwdriver. The wire may also be removed easily from springs in difficult locations too. BTW, if the springs are stretched more than 1/4 of an inch, they are placing way too much load on the ball joints, creating wear that is unnecessary. be careful when welding the tabs on the various parts. Rather than use safety wire, I use one length of 1/16" flexible cable on each exhaust joint that I lace through each eyelet and spring, and then swage with a nico press. I find this much easier, and consider it to be stronger. I too make sure there is a bead on each spring, and at each junction of cable and eyelet to prevent chaffing by the cable. I also made a spring installer/removal out of an old flat blade screwdriver I cut a short slot at a 45 degree angle into the blade. I used a cutting blade on my small hand grinder and it took less than a minute to make. This tool works good, and virtually cost nothing but an old screwdriver that was only good for opening paint cans!