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Why do Rx-1/Apex like to throw #3 Rod out?

sledfvr

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Apr 7, 2008
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NW MT
I bought an Boondocker '03 Rx-1 recently and on my second ride it threw the #3 rod out of the case. I was only running 12-14lbs boost with 30% 110 and 6500ft in elevation with 11.5-12 afr's. And its got a .063 headshim in it. The guy I bought it from had bought the sled as a box of parts and had to put the motor together. He put it together and put the turbo on it at 1000 miles and it only has 1800 miles on it now.
I've been doing lots of reading and it sounds like #3 is usually the rod that lets loose on these motors. It was full of oil and only had 250 miles on an oil change with semi synthetic 0w-30 yamalube. It blew at about 1/4 throttle and made no noise or ticking or vibration prior to that. I'm guessing that maybe the rod bearings had gotten switched around when it was reinstalled, but why is it always #3?
 
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LOYTOY

Member
Nov 29, 2007
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marsden, sk
i have taken the #3 rod out on a boondocker apex three times within 900 km!!! cant figure out why... strait c-16 everytime... no detonation... simply an oil problem to the bearing
 

sledfvr

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Apr 7, 2008
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I wonder if there is an oiling issue on #3. I was also wondering if the header design gets #3 hotter than the rest, I wouldn't think that would result in lower end problems though. I'm not trying to point fingers or anything, I'd just like for it not to happen again.
 
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LOYTOY

Member
Nov 29, 2007
112
19
18
marsden, sk
yeah tell me about it! omg!!! its getting very very expensive for me... I'm on fourth motor! I have friends that have thousands of miles on their boondockers with no problems and I'm on 4th engine! You didnt have a kinked vent line from the case to the oil box by chance did you? I noticed mine was kinked bad and was wondering if it would pressure up a bit and push oil away from that bearing?
 

sledfvr

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When the rod blew out of the block it knocked the vent line out. I will check that when I put it back together though.
 
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BigFish BC

Well-known member
Jan 27, 2005
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kitimat b.c
it is almost always the #3 on apexs center bering on the nytro always the hottest one goes first i know there is a few apexs that have gone over the years at 14-16lbs boost most that i have herd of have been with the boondocker not sure if its the turbo location causing to much heat soak in the block or just bad luck on the boondocker guys.it seems more like a heat issue but thats just a guess ,yet some guys run way more boost & never have a issue.
 
0
Nov 28, 2007
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Vernon
Its a weird thing with engines, if it get's to the point where it's overstressed or oil starved it will usually fail in a predictable way
It's not a weakness in the engine, it was going down anyway due to some setup issue
If a factory were able to make that cylinder tougher, it would just chose the next in line for reasons only an engineer could explain
Same deal with every engine
 
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