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Discussion Starter #1
Hi all, I've just began stripping my engine down for the 2nd time in the last 2 months or so. First time was transmission related - bevel gear upgrade. This time it's related to connecting rod bearing failure after low oil level.

Question is.....if I have no external oil leaks.....where did my engine oil go to (I lost about 2 liters!)? Topped it up last weekend, and after 4 or 5 hours of riding this weekend I ran dry. Lost the connecting rod bearing, hopefully nothing else.

I'm assuming that it has been burned off, it didn't leak through the clutch seals, so I'm assuming either bad rings or bad valve stem seals. Don't think I would lose oil through a bad cylinder head gasket? Strangely, engine did not appear to be smoking at all.

Any advice? Where do these things usually fail?

Thanks
 

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Discussion Starter #5
It's a 2006/650. Ring gaps were on opposite sides of the piston. No signs of oil in the coolant. No issues with performance at all (up until the time it died).

I'm at the point where I am about to split the case, and up to that point the only issue I see is at the connecting rod bearing, it's definitely toast. I was going to pull the piston rings off and have a closer look, checking ring gap, etc. The fact that it wasn't throwing blue smoke makes it a bit of a mystery, but there is no where else that the oil could have gone?!?
 

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It's a 2006/650. Ring gaps were on opposite sides of the piston. No signs of oil in the coolant. No issues with performance at all (up until the time it died).

I'm at the point where I am about to split the case, and up to that point the only issue I see is at the connecting rod bearing, it's definitely toast. I was going to pull the piston rings off and have a closer look, checking ring gap, etc. The fact that it wasn't throwing blue smoke makes it a bit of a mystery, but there is no where else that the oil could have gone?!?
On the ground from a leak in lines to oil cooler?
 

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Well the rings should be at thirds for the best blow by control. It could have made a bunch of crankcase pressure and pumped it past a seal somewhere and leaked out? I would pay attention to the ring gap positions when I took the cylinder off if I was you.♠
It's a 2006/650. Ring gaps were on opposite sides of the piston. No signs of oil in the coolant. No issues with performance at all (up until the time it died).

I'm at the point where I am about to split the case, and up to that point the only issue I see is at the connecting rod bearing, it's definitely toast. I was going to pull the piston rings off and have a closer look, checking ring gap, etc. The fact that it wasn't throwing blue smoke makes it a bit of a mystery, but there is no where else that the oil could have gone?!?


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Discussion Starter #8
No oil on the ground, or anywhere around the engine, including at any seals, and nothing at any of the gasket faces or between left and right engine casings. Clutch casing was 100% oil free. Drain plug was dry and tight. Checked oil lines and cooler, no signs of oil. No oil in the engine coolant. No signs of oil on any of the belly pans.

Worst of all - no oil in the engine!
 

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Discussion Starter #10
I fully agree...it doesn't make sense. And you're probably thinking...."must have leaked out - is this guy blind".....but it never, or if it did, it certainly never left any signs of leaking out.

Anyway, heading back out to the garage to finish the disassembly. Hopefully the crank removal doesn't cause me any grief.

PS. my dealer said he has never heard of an Arctic Cat burning oil?!??
 

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Discussion Starter #11
Looks like the rings may be the culprit (or a part thereof). Just checked the piston ring end gap, never had feeler gauges to make a measurement, but it looks like about 1.5 to 2mm. AC spec says it should be 0.36mm (.014"), even without feeler gauges I know I'm along way from that spec. Will bring feelers home from work tomorrow and measure properly. Should also check the cylinder for trueness I guess.

It's hard to believe that this engine has only about 3000 miles. I've got a 700 Maxim that has 75,000km and doesn't require this much attention.
 

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Not really thinking that just thinking that something has been overlooked. Cause thats what happens to me all the time. It can be staring me right in the face and it might take me awhile to see it.
I fully agree...it doesn't make sense. And you're probably thinking...."must have leaked out - is this guy blind".....but it never, or if it did, it certainly never left any signs of leaking out.

Anyway, heading back out to the garage to finish the disassembly. Hopefully the crank removal doesn't cause me any grief.

PS. my dealer said he has never heard of an Arctic Cat burning oil?!??


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Those are max specs right?
Looks like the rings may be the culprit (or a part thereof). Just checked the piston ring end gap, never had feeler gauges to make a measurement, but it looks like about 1.5 to 2mm. AC spec says it should be 0.36mm (.014"), even without feeler gauges I know I'm along way from that spec. Will bring feelers home from work tomorrow and measure properly. Should also check the cylinder for trueness I guess.

It's hard to believe that this engine has only about 3000 miles. I've got a 700 Maxim that has 75,000km and doesn't require this much attention.


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Discussion Starter #14
LOL....I hear ya sandchris!! Not sure if they are "maximum specs" or "new specs", the AC service manual didn't specify. I did go back and reconfirm the recommended ring spacing though. The 1st/2nd compression rings should be 180 degrees opposite, and the upper/lower of the oil control rings should be staggered about 10-20 degrees from the position of the upper ring. there was a graphic of it, I'll post it later when I get home.
 

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I cant see how this happened this way. If you had little to no oil it should of took out the top end first. We have seen several 650 h1 motors loose the teeth on the oil pump drive gear and the top end really makes noise when there is no oil up there. The crank will get some oil just from the splash effect. Each of the motors with the oil pump not working took out the top first and the crank was still ok. Do you ride in dusty conditions? If that is the case we have seen over one third of the prowlers sold have had the crank fail.
 

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Discussion Starter #16
There may be some truth in what you suggest then. I've only had the machine about a year and ride it in dusty conditions (except for when the snow is on the ground - no dust then). The guy that had it before me drove it in similar conditions.

Of course, a recent bevel gear failure may have contributed to premature failure of the connecting rod bearing as well, ended up with alot of metal filings in the engine. I didn't pay alot of attention to it when I had done the bevel gear work, was concentrating on the transmission. Changed several bearings in the process, but of course the rod bearing isn't very serviceable. That might have been the beginning of the end for the rod bearing though. Couple that with low oil.....and the rest is sad history.

How would you lose teeth on the oil pump drive gear? Do they crack off? Sounds like you're speaking with a great deal of AC experience?
 

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Discussion Starter #17
Well the cylinder measurments were within spec, finally some good news :). Forgot the feeler gauges but used one of the rings to give me an idea of the ring end gap. One was a shade over 1.2mm, the other just a shade less, spec suggests 0.35mm.

I've attached the piston ring placement diagram as provided by AC. The # 5 shows the location of the exhaust valves with respect to the ring placement.
 

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There is a better way in my opinion. I will post up a diagram later.
Well the cylinder measurments were within spec, finally some good news :). Forgot the feeler gauges but used one of the rings to give me an idea of the ring end gap. One was a shade over 1.2mm, the other just a shade less, spec suggests 0.35mm.

I've attached the piston ring placement diagram as provided by AC. The # 5 shows the location of the exhaust valves with respect to the ring placement.


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Big difference on the load on the top end verses the bottom. You are correct about the cranks living even after the oil pump gear is gone. The top ends can still live a little longer that the bottom end with no or little oil. The top end does turn slower than the bottom too. Not as many revolutions right. My guess is that there where some debris left in it from the bevel gear change. And those got into the rod bearing assembly and caused the failure kinda like really dirty from dust oil would. Not that it was not cleaned prior to putting it back together but the pieces or damage was being done as it was nearing the end of the bevel gear. Unless you had the crank rebuilt there could have been some junk hiding in there.
I cant see how this happened this way. If you had little to no oil it should of took out the top end first. We have seen several 650 h1 motors loose the teeth on the oil pump drive gear and the top end really makes noise when there is no oil up there. The crank will get some oil just from the splash effect. Each of the motors with the oil pump not working took out the top first and the crank was still ok. Do you ride in dusty conditions? If that is the case we have seen over one third of the prowlers sold have had the crank fail.


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There may be some truth in what you suggest then. I've only had the machine about a year and ride it in dusty conditions (except for when the snow is on the ground - no dust then). The guy that had it before me drove it in similar conditions.

Of course, a recent bevel gear failure may have contributed to premature failure of the connecting rod bearing as well, ended up with alot of metal filings in the engine. I didn't pay alot of attention to it when I had done the bevel gear work, was concentrating on the transmission. Changed several bearings in the process, but of course the rod bearing isn't very serviceable. That might have been the beginning of the end for the rod bearing though. Couple that with low oil.....and the rest is sad history.

How would you lose teeth on the oil pump drive gear? Do they crack off? Sounds like you're speaking with a great deal of AC experience?
The two that came into the shop did not have any teeth left on the drive gear. If you are working on a 650 H1 06 07 range I would replace it with the new part number Cat has. The Prowlers that have came into my shop with crank failure have all been because of dust. The cylinder also was out of spec so it had to be replaced. Here is one for you. The new price on the 650 H1 motors is low enough that you might look into that. I have bid several and if you do a new cylinder and crank, piston, gaskets labor to split you can put 300 or so more dollars and have a brand new motor. The motors are complete new starter clutch etc. Bolt her in and go, they even have oil in the new motors.
 
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