Hi I have a 2012 rmk pro 800 and I'm getting 100 psi on mag side and 115 on pro side. What is the correct compression for these motors? And also would this be the cause for it coding a de7 code
2012 rmk pro 800 compression
- Thread starter Hoops1985
- Start date
There's no solid number: it varies a lot depending on the gauge, elevation, how hard you can pull, and so on. Usually you kind of have to come up with a "good" number of your own to work off of: at 4000', 135 is the best I've got off one of my sleds. Usually more important is the difference between cylinders: the general rule is less than 5% variation, so that's enough of a difference that I'd be concerned. A leak-down check is far more accurate, but I've got a car that was within 5% on a compression check, but had two cylinders test bad and one very bad on leak-down, so I doubt the news would get better (compression is more of a rough check, leak-down is finer). If you're getting det codes, there's a pretty good chance you've got a blocked fuel filter, bad injector, or other issues to track down. I'd look into the fuel filter first, since those tend to need periodic replacement. Unfortunately, if you're seeing det and compression doesn't match, there's a good chance you need a top end. If you take the y-pipe, exhaust valve, and spark plug out, you can get a pretty good look.
No need to get crazy now dude. Thanks for the info though
So took the motor apart mag side broke a cyclinder skirt off the bottom that sticks down into the case. I think I might be kinda lucky as it didn't punch a hole through my crankcase. I can't find the chunk anywhere might of shot out the exhaust. What are the chances I'm in the clear?
If you can't find any damage and the crank turns smoothly, you're probably in the clear. That said, I don't know how a chunk of piston skirt finds it's way out without bouncing off the crank or rod unless it's pretty small - if it does get through the transfer port, then it can get sucked out the exhaust pretty easily. When I ate a piston, part of the crown broke off and somehow went straight out the exhaust without bouncing around and peening the dome like you often see. Obviously that's a big step closer to the exhaust port though. Anyway, I'd recommend a close inspection as well as (ideally) checking crankshaft runout and rod side clearance (you need a dial indicator and feeler gauges for that, but they're not expensive). If you can't find anything, put it back together and don't worry about it.
There's pitting on the head which I have a new one on the way along with new jugs and it destroyed my reeds but everything seems super smooth and in working condition in the crankcase
R
RHODESIE
Well-known member
how many miles on the crank? if you are planning on keeping it i would opt. for a recon crank. if it ate a cyl skirt chances are debris went through that lower rod bearing. you can also have the upper case machined to accept a 13 and newer monoblock. thicker skirts with less chance of that happening again. 3022352 part # of 2012. 3022449 is the number of the 13,14,15 monoblock. i would closely inspect those cases and the oil squirters.
Just a little over 3000 miles. The lower rod bearing seems very smooth
I'd consider getting the crank rebuilt at that many miles. I sent mine in a little over a year ago because the rod bearing side clearance was out of spec; turns out there wasn't anything terribly wrong with it, but the rod bearings were a little iffy, so those were replaced. It wasn't terribly expensive (I think less than $500), and worth it to me not to have to worry about it. On the other hand, if that's not in the budget and the runout is in spec, it may last you a while. The downside is, you're probably not going to get a warning if it decides to go...
