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how to make a right diagnostic for seized motor?

31K views 23 replies 7 participants last post by  Dunsmoor 
#1 ·
Hi everybody!I need your advise,plz.I heritated "Rancher 350" 2004 with seized motor,what should i do before tearing a motor a-part?When i puling a string of starter,crank is moving a litle bit (1-2 INCH),so my "?" is-what is stuck:top end,bottom end or transmition? Thanks for any opinion!
 
#2 ·
Welcome to the forums. Someone will come along soon who has rebuilt many of the older four stroke engines..One person comes to mind who just did a complete rebuild on one..:) I myself have torn down many an older two stroke engine for top ends, and splt cases for bottom ends that were bad, but they would still turn over fine,,not recommended though,lol! I would get the machine up in the air first and check and make sure that nothing is froze in the drivetrain first, and check for being able to shift the machine into neutral to let the wheels turn to take that off my list, even go as far to having a known good battery in the machine so it will light up the neutral light to help diagnose the issue. Then go to the top end from there would be how I would do it. Any top end that I ever had a meltdown with I could still turn over, it was just scuffed in the cylinder, or a hole in the piston that caused the issue. I've had bad crank bearings also where the engine would still turn also so I would start with what I suggested, unless someone who has worked on these allot has another suggestion. If the piston were actually stuck in the bore from sitting a long time and possibly rusted tight, it could be tough to get the cylinder off. I would get some oil down into the cylinder through the plug hole in the meantime. Good luck.
 
#3 ·
Thank you,"stu5969" for quick response."Neutral" light is "on" ,and transmission shifting manually to "Neutral" easy.ATV rolls easy.Most likely transmission is OK.What do you think,would be wise to get a special scope to look inside of cylinder for rust?I have been told to drain oil from crank case and see,if there is any sign of metal from bearing wear. Thanks again.
 
#7 ·
Thank you,"stu5969" for quick response."Neutral" light is "on" ,and transmission shifting manually to "Neutral" easy.ATV rolls easy.Most likely transmission is OK.What do you think,would be wise to get a special scope to look inside of cylinder for rust?I have been told to drain oil from crank case and see,if there is any sign of metal from bearing wear. Thanks again.
don't know who told you too drain the oil from the crank case ?????????..buttttttt..they are full of it !!.lmfaooo..no need to drain your oil..just to see what your piston looks like !!!..lol..remove the top end ..( the rocker box and head for now )..do what i said with the pull rope..if you can pull the rope...but only so far ????..then i'd say your piston is hitting a bad valve !.
 
#4 ·
i think stu is talking about me..in front of my back !..lmfaooooooo..pull the top end off the motor bro..if the piston is not seized ?..it will turn over when you pull the start rope. let us know how it goes ?. then we'll take it from there.
 
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#5 ·
another way to check it..remove the pull rope from the back of the motor..( yes..it's a bit__h to get to ! )..17mm socket on the crank bolt..turn it clockwise..if you can turn it a good ways ?..then your piston is fine..it's probally hitting a bent or broken valve ?...this will keep you from turning the motor over by hand all the way around.
 
#6 ·
too sum it up ?..there are a few reasons a motor will not turn all the way over..sooo..start with the easy stuff..before you go tearing the motor out of the frame.
 
#8 ·
#11 ·
X2, you won't really know what's wrong until you start taking it apart. Like Shadetree said, remove the top end first.
 
#12 ·
And welcome to the forums.
 
#13 ·
Took the head and cylinder off,big screch on the mirror and jumed rings seats at piston.Any opinion,what would be better,to replace entire standart set of cylinder /piston/rings,or rebore old sleeve and use next size of piston/rings? tnx in advence.
 
#14 ·
well..if the scratch isn't very deep ? ( you can test this with your finger nail )..if you can grab it with your finger nail ?..then it's too deep !..if you can't ?..then you can get buy with just new ring's..and a honing..and it will be fine. hard to tell you what to do here ?..as we can't see the cylinder and so forth. follow my advice..and then you will know which way to go ?. oh..and food for thought..anytime you have it bored out ?..your looking at more cash to rebuild it ( machine work is not cheap ).
 
#15 ·
Thanks again "Shadtree" for advise,but scretch is too deep,so no doubt need to replace the sleeve.Now a have a dilema,how to get a pin out of piston(it's stuck)? 2 stopers had been removed.
Should i take off intire motor to replace top end?thx.
 
#16 · (Edited)
Welcome to da forums...After covering the lower case openings below the piston very well,simply take a propane torch,and heat the piston up on both ends of the wrist pin right at where the piston,and pin meet,just get it too hot to touch,not glowing,or melting hot,and then after turning torch off,spray pb blaster into each end of wrist pin bore,and up through the underside of the piston...Wait until it gets cold,then tap the pin out the side of the piston if you've removed both spring clips from the wrist pin...You also need to check to see if the pistons wrist pin is rotating in the connecting rod end ,or not,and now is the time to figure it out..Take the cylinder to a good machine shop,have them see how much it will need boring,and order the appropriate sized piston and ring kit,along with a top end gasket set...No need for a sleeve unless the one in your cylinder now is bored to the max,loose,or cracked...
 
#18 ·
if yer piston is stuck on the connecting rod ?..i always just take the right size socket..and an exstension..and whack it out from one side or the other. i've never used a torch to heat them ..not saying it won't work !!!..as deep said..yeah..your gonna need your cylinder bored over to one size larger. yu'll need a new piston and ring's. who ever is gonna bore it ?..they need to tell you what the next size piston and ring's you will need ??..VERY IMPORTANT : if you go with a wiseco piston ?..MAKE DAMN SURE YOU GET THE COMPLETE PISTON KIT !!!..i say this..because if you buy just a wiseco piston..and some other ring's from someone else ?..the ring's will NOT FIT THE PISTON !!..ONLY WISECO RING'S WILL FIT ON A WISECO PISTON !!!.
 
#21 ·
How desperet i need to take the piston out from a rod? I made deeper reserch and looks like cylinder has no deep scretches.As "Shedtree" saes -"not feelable with nail".Should i replace the rings for sure,or i can use old ones?They looks good to me.Tnx.
remove the top ring from the piston..slide it down inside the cylinder..then turn it inside the cylinder as if it were on the piston..then see what your end gap look's like ?. if it's too big ?..then replace the rings.
 
#22 ·
OK,guys,i'v been able to assamble the motor and started up.Conclusion:somebody was so smart to put oil filter up-side down,and that coused the problem.You will be surprised,but all of my expenses is one piston pin stoper and new oil filter with 2 Q.of oil.
Looks like i was lucky that time.Any way i would like to thank you for your advises and wish you good luck as well.TNX.
 
#23 ·
STOP! STOP! STOP!

Before you do anything. Pull the spark plug and turn it over to dry the pool of gasoline that has settled in the cylinder leaking through the bad float valve on the carburetor. After drying the cylinder by turning the engine over with no spark plug in the hole, put a new spark plug in place start it up. As long as the engine is running it will run perfectly (probably) until you get to your destination where you can rebuild the carburetor or, if you are really good, clean the float valve and get on with the ride.
 
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