Jgoodsell 19 #1 Posted November 25, 2019 All, thanks for looking and please let me know your thoughts. I have a 518h year unknown and hours around 750 I think the last time I looked. I recently lost spark so I went on a replacement spree trying to locate the issue and solved that issue. But as soon as I fixed one, I get another. The new issue is that it seems it is running rich. I cannot get it to run smoothly wide open and if I try putting it under load (activating 2-stage blower just on and not pushing snow) it bogs down and sometimes backfires. It also sometimes backfires when just trying to run it wide open. I have so far replaced pickup coil, plugs, plug wires, coil, carb (working from another tractor and was cleaned before putting in place), and I'm sure there is something else I'm missing. I tried running it with each plug running one at a time and it run with each plug separately, be it not well on one cylinder but it does run. New gas was put in, no change. Tried adjusting the screw on the side of the carb facing the exhaust, but no change. Before summer the heads were de-carboned and the valves were checked. Tried running without air filter with no change. Running with no filter is what allowed me to notice that the gas was sometimes spraying out the top of the carb. Sometimes shooting flames if I try to run it with full throttle. Any suggestions appreciated!! Share this post Link to post Share on other sites
lynnmor 7,823 #2 Posted November 25, 2019 Check the compression first thing, report back. Sounds like it is running lean, not rich. A lean mixture can cause a backfire out the carb. Even though you swapped carbs, I would still disassemble and clean any carb before installation. You said the valves were checked, were they adjusted? That screw on the side of the carb is the idle mixture screw. 2 Share this post Link to post Share on other sites
