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Discussion Starter · #1 ·
Picked this up a few days ago ... it's an ES & the owner said it had shifting issues & had been sitting for roughly 6-mos to a year. Battery was dead of course.

Got it home and checked it out ... seems to shift through all gears just fine & fired right up with a power pack. However, when idling, I'm hearing the noise in the video below .... what am I looking at, upper, lower, valves, or ???

 

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Sounds like the big end of the connecting rod is knocking. If so, at a minimum it'll need to be split for a crankshaft rebuild or replacement. Expect worse...

Its easy to verify whether it is the big end of the rod or not though.

Good luck,

Edit:
I've heard clutches sound that bad too, so its gotta be diagnosed...
 

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Discussion Starter · #3 ·
Its easy to verify whether it is the big end of the rod or not though.

Good luck,

Edit:
I've heard clutches sound that bad too, so its gotta be diagnosed...
Thanks for that; advice on how to verify the rod?

Can the clutch cover be pulled w/ the engine in? Or is removal necessary?
 

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Thanks for that; advice on how to verify the rod?

Can the clutch cover be pulled w/ the engine in? Or is removal necessary?
I verify without pulling anything off the motor except for the spark plug and flywheel plug. I use a dial indicator in the plug hole in the head to monitor piston movement while turning the crank back and forth.

You can also crank the motor by hand until it is halfway up into the compression stroke and then rock the crank back and forth a bit at that point, as the piston will tend to stay put well enough to allow you to feel (and hear) a sloppy rod bearing.

Your knocking is a bit too severe for it to be the wrist pin end of the rod, in my opinion. But you gotta learn yourself cause a video on a forum isn't worth anything... And as I said, I've heard clutches and a number of other bad parts make the same racket so ya gotta diagnose it to be certain.

Let us know what you learn,
 

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Discussion Starter · #5 ·
You can also crank the motor by hand until it is halfway up into the compression stroke and then rock the crank back and forth a bit at that point, as the piston will tend to stay put well enough to allow you to feel (and hear) a sloppy rod bearing.
"Crank by hand" ... I need some schooling on this - I can obviously use the starter button; but, its difficult to control the piston position. This model does not have a pull rope.

So far, I've bore-scoped the piston/cylinder - nothing looks abnormal. Engine fires right up easily - I happened to have the dipstick out when running & noticed air pushing out of the crankcase (normal?).
 

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There should be a plug that you can take out with a screwdriver in the middle of the engine side cover. Once that cover plug is out you can use a socket and a short breaker bar to rotate the crankshaft by hand. With the spark plug still in the head you'll be able to feel the compression stroke resistance as you crank the motor in its normal direction of rotation. Part way into the compression stroke... stop cranking and just rock the crankshaft back and forth with your socket. You should be able to "feel" a sloppy rod bearing doing this.

See the service manual for additional info... the cover plug should be mentioned in the camshaft/cam chain area (possibly the ignition area too) of the manual.

The SM for your model can be found HERE.

EDIT:
Yes, while the motor is running with the dipstick out you will see the crankcase breathing. This is normal behavior with the dipstick out on a running motor. You may get some oil spray/mist wetting your ear with an uncapped case too. :)
 

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Discussion Starter · #7 ·
It's a mystery still ... crank seems tight, valves look good, only thing I noticed was an audible "click" on the up compression stroke (cranking by hand/ratchet).

Guess the engines coming out for a more in depth look. =(
 

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Wow. I've never heard something that severe from a Rancher 420. Yowza. Tell us what comes of it!
 

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Discussion Starter · #11 ·
Finally got around to cleaning (pressure washing) the engine over the weekend; and, this afternoon, I removed the head & cylinder.

No evidence of water / sand in the crankcase. The head looks pretty good. No up/down movement on the rod that I can detect; but, there was some side-to-side (normal?). The piston skirts look bad to me; and, so do the adjacent cylinder walls. Rings look fine.

What do you see (sorry for the one blurry pic)???



















 

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Its done... The bore & piston is shot. The connecting rod is blue and black from getting smokin' hot... which means the wrist pin and upper end of the rod are shot at a minimum.

At this point the cases will have to be split for a replacement (or rebuild) crankshaft and rod assembly. The cost for a crankshaft may be cheap or expensive, depending on what you end up buying. The cylinder and the head can be sent to G&H for a fresh bore & piston kit & head/valves done. A lower end engine gasket set & any other parts you find bad in there, a few seals, bearings etc., along with your shop supplies will probably set you back between $600 - $1k, depending on your decisions...

Best of luck,
 

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Its done... The bore & piston is shot. The connecting rod is blue and black from getting smokin' hot... which means the wrist pin and upper end of the rod are shot at a minimum.

At this point the cases will have to be split for a replacement (or rebuild) crankshaft and rod assembly. The cost for a crankshaft may be cheap or expensive, depending on what you end up buying. The cylinder and the head can be sent to G&H for a fresh bore & piston kit & head/valves done. A lower end engine gasket set & any other parts you find bad in there, a few seals, bearings etc., along with your shop supplies will probably set you back between $600 - $1k, depending on your decisions...

Best of luck,
just a heads up ?, all connecting rods are blue from the factory !. they are this color because they temper them. but !!..you are correct !, the piston , bore, and more than likely, the connecting rod is toasted. a complete engine tear down is on the list for this motor.
 
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OP, count on a crank ( unless you can get a new connecting rod pressed on ?, new piston kit, complete engine gasket kit, may as well replace all the oil seals while your tearing it apart !. cylinder will need to be bored over if it's not maxed out already ?. if it's still within specs ?, calls for a bored cylinder to the next size up. if I had to guess by looking at this damage ?, I would say it was either sank ?, or ran low on oil ?.
 

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Thanks for correcting me shadetree! I know some are blue, others are blue somewhat near the ends etc., wasn't completely sure about this one.... But like you said, its probably toast judging from the piston damage and the unknowns yet to be discovered in the crankcase. I wonder if the coolant system failed (blown seal/pump?) and took it all down or if it was sunk or run out of oil...?

@ OxFactor
Was the motor (and system) completely full of coolant or was it low/empty when you tore it down? Was it full of oil? Clean or...?

Thanks,
 

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Discussion Starter · #16 ·
@ OxFactor
Was the motor (and system) completely full of coolant or was it low/empty when you tore it down? Was it full of oil? Clean or...?

Thanks,
Previous owner sold it to me as having a "trans issue" - not cranked in 6-mths or more. I assumed it was ES related & took the bait. In my own ignorance, I took a power pack & cranked the engine before buying & heard the knock clearly - but, knowing it hadn't ran in several months, I shut it off quick & wrote it off as being dry. I didn't get much info outside of that ... it was a teenager.

The ATV was low on oil, and it was dark. No fragments were in the filter. Coolant was full & green - fan works, but can't say if it was coming on properly or if the coolant was actually circulating. There's evidence that the ATV may have tipped on its side or rolled. It was muddy, like most - may have been swamped. Based on the piston apron condition - I say starved of oil, or water got in.

More pics & videos ... note in the video the side-to-side movement of the rod; I can't detect by hand any up & down movement.










 

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take the wrist pin, stick the very end of it, just enough to go the full length of the connecting rod, then lift and push down from the outside end of the wrist pin, got play ?, if so ?, your connecting rod is bad. if not ?, then your connecting rod is good to run, but you will still need the cylinder bored, new piston kit.
 

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the reason I say to use the very end of the wrist pin ?, is because this area of the wrist pin does not see wear like the very middle does !.
 

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^^^^ What shadetree says! ^^^^ Very wise words indeed!

You'll also appreciate having that length of wrist pin stuck in the top of the rod to use to apply some extra force and leverage on the lower rod bearing while looking for play in that too! You can miss some loose lower rod bearing problems using just your fingers to pull and push on them... I can anyway...

As shadetree generously shared, the wrist pin wears the most in the center of it, in the bore at the top of the rod. If it fits good in the rod using the end of it it will probably measure as being good too.

You can check the lower rod bearing endplay clearance with some feeler gauges, if ya got some that go thin enough. The specs for all are in the FSM at the beginning of the appropriate chapter/section for each component.

Come back and share what you find out...
 

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Discussion Starter · #20 ·
take the wrist pin, stick the very end of it, just enough to go the full length of the connecting rod, then lift and push down from the outside end of the wrist pin, got play ?, if so ?, your connecting rod is bad. if not ?, then your connecting rod is good to run, but you will still need the cylinder bored, new piston kit.
Yes ... performed this test this afternoon - there is a very small amount of play up/down when the wrist pin is inserted into the con rod as you described. Not a lot of play, but I can detect movement. :eek
 
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