toolucky Posted February 8, 2009 Report Posted February 8, 2009 I have a 421 cheetah PV motor built and broken in by Trinity. Ive been running 155 mains and 50 pilots with needle on middle clip. 1 1\2 turns out on the air fuel screw. the temperature has ben in the 40s here and im at 850 elevation. Running the 35 pwks 111 race fuel and Belray H1R synthetic. havnt really had any complaints until yesterday, the temp got up in the mid 60s but i just left the jetting like it was and rode. The water temp gauge never gets above 160. later in the evening the bike was having a WOT bog almost like it was staving for fuel so i headed home checkd the plugs and they were a dark tan almost chocalate but i put in new ones anyway. started the bike up and let it idle for a minute then it just seized. couldnt budge the kick starter. finally freed it up and it kicks over just fine. what would have made it do that? Quote
lowbuckracing Posted February 8, 2009 Report Posted February 8, 2009 Do a compression test...before running it again..Keep us posted. Quote
blaster2006 Posted February 8, 2009 Report Posted February 8, 2009 I have a 421 cheetah PV motor built and broken in by Trinity. Ive been running 155 mains and 50 pilots with needle on middle clip. 1 1\2 turns out on the air fuel screw. the temperature has ben in the 40s here and im at 850 elevation. Running the 35 pwks 111 race fuel and Belray H1R synthetic. havnt really had any complaints until yesterday, the temp got up in the mid 60s but i just left the jetting like it was and rode. The water temp gauge never gets above 160. later in the evening the bike was having a WOT bog almost like it was staving for fuel so i headed home checkd the plugs and they were a dark tan almost chocalate but i put in new ones anyway. started the bike up and let it idle for a minute then it just seized. couldnt budge the kick starter. finally freed it up and it kicks over just fine. what would have made it do that? exactly the same thing happened to a friend of mine, the kicker seized then it would kick over again, and when it kicks he described it as "you dont feel its trying to start at all anymore when you kick it" the problem was he needed a new bore + pistons, they could not tell exactly what the problem was for but they think water came in from the radiator into the cylinders and blew it up. his bike runs fine now after overbore + pistons. Quote
locogato11283 Posted February 8, 2009 Report Posted February 8, 2009 your jetting should be rich now after going from 40 degrees to 60. the dark tan or chocolate indicates it is rich. new plugs wont fix this, only rejetting will. maybe you busted a ring and it caused it to jam up. sounds like you might need to pull the cylinders to see whats going on. Quote
sleeper06 Posted February 8, 2009 Report Posted February 8, 2009 At least take the head off . Ive seen some crappy powervalve installs on dirtbikes thatcause seizure do to contact with power valve,Wot bog could be powervalve hanging up,im also not sure if thePV set up on cheetahs is the same on KXs. Definitally worth a shot Quote
dragbanshee Posted February 8, 2009 Report Posted February 8, 2009 Wasn't toolucky yesterday huh, may have been lean from the start, and just caught up with ya. Like loco said, it would have richened up if anything. Welcome to the site, and good luck! Quote
Snopczynski Posted February 8, 2009 Report Posted February 8, 2009 From what you describe it sounds like it seized, so heat would cause that. Usually if they get hot, they seize up, and then cool off and loosen up. FOLKS when you say what clip position your needles on, we also usually should know what size needle it is. You always give us main, and pilot size, lets finish it off with the needle size. Quote
blowit Posted February 8, 2009 Report Posted February 8, 2009 We do not believe in just running an engine after seizure unless in a race situation. You are assured damage of some sort in the engine and the jugs need pulled to determine the source. I am leaning towards over heat at this time. Not sure what caused it yet but get it apart and show pics and we can help from there. Where is the water temp sensor at? Should be reading water coming out of the head. Brandon Quote
toolucky Posted February 8, 2009 Author Report Posted February 8, 2009 Do a compression test...before running it again..Keep us posted. did a comp test and one side messures 140 and one side measures 130. i saw some stamping on the top of the head were the plug goes in and it 68.5-----19-----10. im assuming the 19 means dome size Quote
toolucky Posted February 8, 2009 Author Report Posted February 8, 2009 We do not believe in just running an engine after seizure unless in a race situation. You are assured damage of some sort in the engine and the jugs need pulled to determine the source. I am leaning towards over heat at this time. Not sure what caused it yet but get it apart and show pics and we can help from there. Where is the water temp sensor at? Should be reading water coming out of the head. Brandon water temp sensor is actually located between the case cover and the bottem of rhe radiator Quote
toolucky Posted February 8, 2009 Author Report Posted February 8, 2009 your jetting should be rich now after going from 40 degrees to 60. the dark tan or chocolate indicates it is rich. new plugs wont fix this, only rejetting will. maybe you busted a ring and it caused it to jam up. sounds like you might need to pull the cylinders to see whats going on. i knew the jetting would be rich with this temp change but would that cause it to sieze Quote
toolucky Posted February 8, 2009 Author Report Posted February 8, 2009 From what you describe it sounds like it seized, so heat would cause that. Usually if they get hot, they seize up, and then cool off and loosen up. FOLKS when you say what clip position your needles on, we also usually should know what size needle it is. You always give us main, and pilot size, lets finish it off with the needle size. the needle says CEL Quote
blowit Posted February 8, 2009 Report Posted February 8, 2009 (edited) My previous post sounded a bit assish. sorry for that. I would recommend removing the cylinders and see what you have. Because of where the water temp sensor was, it was reading cooled water going back into the engine, not the hot water coming from the engine. I suspect the engine simply overheated. An engine will bog and run weak when hot. Overheat could have been caused by a number of things. Leaking coolant system, lack of air flow, low coolant level, etc. Hopefully you can get away with some piston cleanup if the rings are not welded into the pistons. Brandon Edited February 8, 2009 by blowit Quote
toolucky Posted February 9, 2009 Author Report Posted February 9, 2009 My previous post sounded a bit assish. sorry for that. I would recommend removing the cylinders and see what you have. Because of where the water temp sensor was, it was reading cooled water going back into the engine, not the hot water coming from the engine. I suspect the engine simply overheated. An engine will bog and run weak when hot. Overheat could have been caused by a number of things. Leaking coolant system, lack of air flow, low coolant level, etc. Hopefully you can get away with some piston cleanup if the rings are not welded into the pistons. Brandon thanks for all the info everyone i will pull the cylinders and see whats up and try to post pics. Quote
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