Hey everyone, I’ve been browsing the forums here for some time but finally decided I needed to join. So, to my problem, I bought a 2013 KFX450r in hopes to upgrade from my 2001 Mojave 250 as I was getting left behind on straight aways on trails. When I got it, I changed the fluids and oil filter. Then, I took the quad for its first ride, put about 2-3 hours on it, and it started backfiring/after-firing and making a rattling noise. I brought it to a shop to get checked out, was told the bottom end is toast and needs a full rebuild. What I don’t understand is the shop only checked the compression (which was low) and the oil filter. So, does anyone know how this shop knows the rod bearings and bottom end are toast just by seeing low compression. I was also told the engine was knocking but like I said earlier, the only noise was a rattle coming from the top end/radiator area and was definitely not a knock. I apologize for the long post but this machine was a big purchase for me and it doesn’t make sense, according to the symptoms and based on my knowledge, that I need to drop $2,500 on a rebuild. I appreciate any insight.