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Discussion Starter · #1 ·
I was running yesterday and started loosing power. Came home and did a compression test, 20 psi mag, 145 pto. I started tearing down the engine thinking I had melted a piston and noticed the decompression plug on the mag side was out against the fuel rail. The head was off and the piston and cylinder looked fine. I replaced the orings on both plugs, cleaned them and loctight, then reinstalled. Started it up and it runs alot better but still have a low idle (1100-1200 rpm). Rechecked the compression 145 pto, 110 mag. This explains the low idle but what happened? Did the rings get cooked from the plug falling out? Do I need a rebuild? Any info whould be great. Has anyone else had a decompression plug rattle out?
 

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Edit

If the decompression plug rattled out, that's because it was was not put in place properly. With 110 compression on the same side that the plug fell out, it's the likely cause.

I have no doubt you already know the price for a rebuild, and there is plenty of time and money to be invested. It sounds like you're planning on putting a set of rings and pistons to finish the season, and want to make sure there is nothing else but the plug to worry about. I wish it were that easy, but there is something you can do to put the chances on your side, and that's some basic testing and cleaning. A leak test for the engine would do, and you can buy the parts and build a basic test within a couple of hours for maybe $50. Also clean the gorunds.

With a little help from an ohm meter you can give the sensors a quick test. Then check the CTS and EGT wires are not wearing against any hot coolant hoses. Also check LP pump wires are not rubbing against the engine. With a volt meter you can check the battery. A very basic low pressure fuel pump test is easy to achieve. E-RAVE adjustment won't take long. There is lots of easy testing you could do in a day.
 

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Discussion Starter · #7 ·
I have the plug on the right. When I found it loose I cleaned it, replaced the o-ring and put locktight on the threads. I've pulled the head, piston and cylinder look like new. Could the rings be cooked from this falling out?
 

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I have the plug on the right. When I found it loose I cleaned it, replaced the o-ring and put locktight on the threads. I've pulled the head, piston and cylinder look like new. Could the rings be cooked from this falling out?
The one on the right is the plugs with the active decompression circuit. One of your plugs may be actually plugged and the other not and this is your difference in cranking compression. Just some thoughts. The plugs on the left are worth a couple of horsepower.
 

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I just edited my post because I realized you're probably anxious to finish the season without a total engine rebuild. If your cylinders and pistons don't have too much scoring, maybe you can get away with it. But a complete set of tests will go a long way to make it work.
 

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Discussion Starter · #10 ·
I removed both plugs and did the same to the plug on the pto side as the mag side. Is the plug on the left the upgrade plug? Any thoughts as to burnt rings? The rings and sides of the piston are the only thing I can't see. Just don't want to pull the jugs if I don't have to.
 

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You can count yourself lucky to have no scoring on the cylinders. With that low compression, I don't think you have a choice to pull the top end. The intake and exhaust side of the pistons and rings can be seen without removing the monoblock, but that won't help fix the low compression.
 

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Discussion Starter · #13 ·
My whole sled has had the grounds rewired with heavyer wire. E-raves have been removed and cleaned. Fuel pump is upgraded and relocated for easier access. How would any of this affect my compression in the cylinder?
 

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It doesn't. I'm thinking after putting rings or whatever it needs to fix the compression issue, might as well do a leak test to insure you're rebuild. By the sound of your last post, you seem to be on top of things.
 

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Discussion Starter · #15 ·
Pulled the block and found a broke ring and bad piston. Just placed my order for a top end kit, wiseco. Is there anything special I need to do other than hone the cylinder?
 

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leave some on the extra wiseco has a range measurement id go to the bigger side wisecos being of the forged material the will grow with heating. i think the lack of a thermostat in these engines also contributes to the wisecos seizure if the tempature could be more consistant. i noticed it dont take to long to warm up not nessacaryily overhear but one second your real cool then you sit for a bit, maybe pick a different line and it starts to climb a bit then you take off the powder cools it right off.
 

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Discussion Starter · #19 ·
Wisecos come with the correct cylinder measurement right in the box. They don't give you a range for bore size, at least the last ones I got didn't. My guestion was about honeing the cylinders. Do you just hone untill you reach the size wiseco states?
 
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