XXitanium Posted February 17, 2022 Share Posted February 17, 2022 Carbureted an-air-wrecks-ia ...lean condition? Paired with snow dust, @varing rpms approx & 10F = concave piston head, melted? The compression went to 30 PSI in one jug. The other job was okay at about 130 PSI. The good pistonhead dings in the head from something bouncing through on its way out the exhaust. These engines have a thing on the exhaust called a rave valve. I think it's the same cylinder that the rave valve spring head popped off before we took it to the shop for the fall tune up. I guess I don't mind fixing it. My mechanic says it has been open before. The pistons are non-stock. It is at the first over-bore. I'd like to avoid future issues. I read a few threads and they seem to all agree that this model year, came from the factory with a stock lean condition. I've looked at a few different forms as well. Any of y'all care to chime in? https://www.snowmobileworld.com/threads/help-problems-w-500ss.51598/ I guess if you open up the bore and don't do anything with the carburetor you're probably making it just that little bit more lean too, right? Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted February 17, 2022 Share Posted February 17, 2022 I don't know these, but spent a fair bit of time playing with SeaDoos with the 800 Rave motor. By all accounts, it's a great motor. Damn near everyone says to run only the factory branded oil, or some other 'super premium' oil, crappy oil will gum up the Rave valve. I would possibly run Yamaha Ring Free in it also, it seems to do wonders on keeping things clean. A stuck or broken Rave could upset the air/fuel ratio and if it's already borderline it could push it over the edge. 1 Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 17, 2022 Author Share Posted February 17, 2022 (edited) I've been told Skidoo Mineral Oil. I had $52 per gallon Amsoil in it though. I also read that the rave valves relaxed and contacted the piston skirts after "some miles". Edited February 17, 2022 by XXitanium Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 17, 2022 Author Share Posted February 17, 2022 (edited) 4,000 miles should still be in break-in - my world. Could have still been in the rebuild break-in? Edited February 17, 2022 by XXitanium Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 17, 2022 Author Share Posted February 17, 2022 Some guy said a mouse nest in the muffler or collapsed baffles raise havoc as well. Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted February 17, 2022 Share Posted February 17, 2022 4 hours ago, XXitanium said: I also read that the rave valves relaxed and contacted the piston skirts after "some miles". My recollection is that the valve moves vertically in a channel in the exhaust port and can't make contact with the piston. I guess if a valve broke then pieces could go into the cylinder/piston, but I never heard of that happening. Quote Link to comment Share on other sites More sharing options...
XXBirdSlapper Posted February 17, 2022 Share Posted February 17, 2022 How soon after start up did it fail? Any symptoms before the failure? Hard starting or bogging/dying? Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 18, 2022 Author Share Posted February 18, 2022 It ran great all day, we put on about 70 miles. We were running twisted woods trails running on old fire lanes, and through swamps. There were a couple small lakes where we could open it up. It seemed to start and run well the whole time. A sign you are loosing compression.... These are designed to run the engine backwards for reverse. To get reverse, you blip the start button. The ECM stops the engine BTDC and that allows te compressed gas/air in the cylinder to start it backwards. When it doesn't start backwards, you've probably lost compression. When we got back to the trailer to load it, it had trouble starting in reverse. I took it to the shop to drop off for a hand warmer. I got it started on the trailer, but then I couldn't back it off, it died and wouldn't start again. Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 20, 2022 Author Share Posted February 20, 2022 ...detonation maybe? Piston Failue.pdf Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 20, 2022 Author Share Posted February 20, 2022 Piston on the left with the black spot was described as melted. The one on the right has little tiny pock marks. Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 20, 2022 Author Share Posted February 20, 2022 Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 20, 2022 Author Share Posted February 20, 2022 This was jambed in one of her ski hinges and caused an 18" tall rooster tail of snow. It went on for a couple hundred yards. Snow ingestion? Quote Link to comment Share on other sites More sharing options...
superhawk996 Posted February 20, 2022 Share Posted February 20, 2022 I don't see melted. The pock marks look like impacts from something that got in there, if the head has matching marks then it's likely what happened. Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 20, 2022 Author Share Posted February 20, 2022 Detonation is what the Ski-doo forum guys think. Bad gas? Glycol leak? One piston lean, one piston pre-igniting? It's weird. It seemed to run well on the rebuild though. 1 Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 21, 2022 Author Share Posted February 21, 2022 https://www.dynamicefi.com/SparkPlug.php Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 21, 2022 Author Share Posted February 21, 2022 "Two Stroke Detonation Story from Millenium Technologies – LINK HERE The most common mode of failure for 2-stroke engines is detonation. We asked 3 time AMA pro mechanic of the year, multiple SX/MX championship winning crew chief, and Millennium Technologies Technical Manager, Tom Morgan to put together brief guide on two stroke detonation and how to prevent it. We hope its helpful." http://www.tomdonneymotors.com/2019/06/11/2-stroke-detonation/ Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 21, 2022 Author Share Posted February 21, 2022 Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 21, 2022 Author Share Posted February 21, 2022 "Two Stroke Detonation Story from Millenium Technologies – LINK HERE The most common mode of failure for 2-stroke engines is detonation. We asked 3 time AMA pro mechanic of the year, multiple SX/MX championship winning crew chief, and Millennium Technologies Technical Manager, Tom Morgan to put together brief guide on two stroke detonation and how to prevent it. We hope its helpful." http://www.tomdonneymotors.com/2019/06/11/2-stroke-detonation/ Quote Link to comment Share on other sites More sharing options...
blackhawkxx Posted February 22, 2022 Share Posted February 22, 2022 On 2/20/2022 at 12:34 AM, XXitanium said: This was jambed in one of her ski hinges and caused an 18" tall rooster tail of snow. It went on for a couple hundred yards. Snow ingestion? Did you ever find the rest of him? Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 23, 2022 Author Share Posted February 23, 2022 I think maybe he caused the detonation as he went through the carbs and cylinders? Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 23, 2022 Author Share Posted February 23, 2022 (edited) ... Edited February 23, 2022 by XXitanium Quote Link to comment Share on other sites More sharing options...
XXitanium Posted February 23, 2022 Author Share Posted February 23, 2022 (edited) .... Edited February 23, 2022 by XXitanium Quote Link to comment Share on other sites More sharing options...
XXitanium Posted March 21 Author Share Posted March 21 Quote Link to comment Share on other sites More sharing options...
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