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New Rebuild Ruined

2012 Pro RMK 800, rebuilt the engine myself. After 150 miles, why would a piston wrist pin circlip fall out, it was definitely seated in the groove properly?
 
It may have looked that way but it may have gotten bent putting in, I have had that happen with Polaris clips. Always caught it when it happened but that may be a possibility.
 
OK, so I've rebuilt the engine since my circlip incident, yesterday I went out for an easy trail ride to break it in, I put some oil in the gas at around 100/1, I let the engine warm up to about 120 degrees and started down the trail, about 1 mile from the truck I was just cruising at about 40 mph around 6000 rpm's and about 1/4 throttle, the temp was 129 and the scratchers were down when the engine just locked up. When I tried pulling on the starter, still locked up, about a minute and a half later I pulled on the starter and the engine turned so I gave it 2 good pulls and it started, idled and sounded just fine. So we decided to keep going, we did some heat cycles through the day and got in about 60 miles with no other problems. What could have possibly happened with the engine locking up? None of the oil lines were disconnected except the oil tank and when I reinstalled the oil tank I filled the tube to the top and reattached it to the tank, it didn't take much. I did check ring end gap clearance, I had to file down a little bit because it was to tight, I was very careful and all four are in spec. I also oiled all parts before installing.
 
Did you bleed the oil pump after reconnecting the oil line to get any air out of the line?
 
Did you bleed the oil pump after reconnecting the oil line to get any air out of the line?
I clamped the line when I removed it from the tank, then when it was time to reconnect it, I used a syringe to fill the tube up to the top, which didn't take much, and then reconnected to the tank. Do you think there should have been a reason to bleed the pump if none of the other lines around the engine were disconnected?
 
I had a whale of a time bleeding the oil line when I did my top end recently. I opened the bleed, took the bolt out completely even, and let it dribble onto a shop towel until it seemed to be flowing steadily. Then I noticed the line still looked dry. This was with Legend oil, which is pretty thin, so it must have been flowing down the tube. I ended up fishing a cap from some jug down there, taking the bolt out, and blowing into the oil tank and finally cleared the air out of the line. I'm not sure that's likely to be your problem, but making sure the line from the tank to the pump doesn't have the slightest bubble in it is critical. The lines from the pump to the engine aren't critical: they will clear on their own because they're downstream. I think Polaris even says the can have small air bubbles in them. Anyway, if it locked up, I'd pull the exhaust valves and Y-pipe and get a good look. There's probably some damage, but you might get some life out of it.
 
Its better safe than sorry on it. I bled mine and did not see any air, but I was steadily testing because I was not getting sufficient oil. Mine ended up being the mag side bearing and mag side cylinder oil lines being hooked up backwards. Also when you fire up a new engine, you should hook a metal coat hanger up to the oil pump level and pull it wide open while its running for a couple minutes to ensure you get all air out and bubbles out of the system.
 
Its better safe than sorry on it. I bled mine and did not see any air, but I was steadily testing because I was not getting sufficient oil. Mine ended up being the mag side bearing and mag side cylinder oil lines being hooked up backwards. Also when you fire up a new engine, you should hook a metal coat hanger up to the oil pump level and pull it wide open while its running for a couple minutes to ensure you get all air out and bubbles out of the sy
OK, so I've rebuilt the engine since my circlip incident, yesterday I went out for an easy trail ride to break it in, I put some oil in the gas at around 100/1, I let the engine warm up to about 120 degrees and started down the trail, about 1 mile from the truck I was just cruising at about 40 mph around 6000 rpm's and about 1/4 throttle, the temp was 129 and the scratchers were down when the engine just locked up. When I tried pulling on the starter, still locked up, about a minute and a half later I pulled on the starter and the engine turned so I gave it 2 good pulls and it started, idled and sounded just fine. So we decided to keep going, we did some heat cycles through the day and got in about 60 miles with no other problems. What could have possibly happened with the engine locking up? None of the oil lines were disconnected except the oil tank and when I reinstalled the oil tank I filled the tube to the top and reattached it to the tank, it didn't take much. I did check ring end gap clearance, I had to file down a little bit because it was to tight, I was very careful and all four are in spec. I also oiled all parts before installing.
Here's the video of it locking up.
 
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