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mavgrab302

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Not the place to really ask the question but I have more confidence ppl in here rather than a bunch of kids on an ATV forum that will tell me to check the jetting...lol

Ok so I bought a 2008 trx450er that I couldnt test as I normally would being it was an apartment complex, I get home and kick myself after riding and hearing the engine. It had a pretty noticeable knocking, sounded like crank hitting the case/piston slap/rod or something along that line, getting progressively worse after five min of riding clutch in or out didnt matter so. it is a consistant mechanical knock, not erratic. The obvious next step, dig in to it. I get to the point where I pull the cylinder off and notice the middle of piston skirt (forward side) had a nice shiny spot like it was machined down to shine lol, I checked rod journal it was within spec, no wiggle in crank everything smooth so thought well heck I guess it was just time to change the piston.
I buy a new athena 96mm kit (used athena before on KFX) and just go back std bore, mind you this is a cylinder and piston kit. put it all back together and within minutes same noise, after about 15 minutes I decided to tear back into it. And what the heck after 15 minutes of running the athena kit (carillo piston) had already started to displace material on piston skirt in pretty much the same spot ( wore coating off carillo piston) right in the center lower part of skirt so much so that while not shiny YET it was removing the small machined lining.
Long story short I figured wth I'm just going to build it all over a mindset of process of elimination I thought I'll just replace linked parts with new piston/rod/crank/bearings etc.. It has to be crank bearing, rod crank or something, no vavle contact, timed correct so then bought 510cc kit (+3mm crank, 100 mm piston, all new bearings for crank, tranny, clutches, seals everything new except cases, actual tranny gears, clutch basket, cam since (clearances are good). I get it all back together and this same noise. Now I know I have heard some videos very similar to mine and comments say "oh it's normal" but I just know from experience something is not, it is quite at first then gets louder as engine heats up it seems, then is noticeable even at idle. That all said it is a thick sounding noise, not a noise you'd get from valves, cam/vavle slap etc. I did notice the clutch basket that is connected to fly wheel wiggles slightly (other vids I have seen says this is normal/bad design which I agree) can that send out a noise that reverberates through the entire motor? I don't believe it is the basket but as I have stated I am getting desperate. Using a stethoscope it is very hard to nail down where the sound is coming from too. Being everything has been replaced except, cam, valves, clutch basket/flywheel I am just at a lose and never really been defeated when it comes to this sort of stuff. To be clear it is not anything to do with valve train (cam,valves,etc) and the piston was correct for bore and rings were all filed or in spec... I have even put 110 octane just to eliminate if it was detonation and it still did it...So my question is this since in basic theory all piston combustion engines are basically the same it has done the same exact thing to the new kit (wearing piston skirt out within minutes) what would cause this?
from AMC 410 jet boat build to a 347 maverick to several KFX400/450 I have never ran into this problem and I am at a loss at this point..A big thanks to anyone that can help..What would cause a piston skirt to wear like this?
 

Pighuntingpuppy

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Whats the transmission like? Worn bearing in one of the mainshafts sound EXACTLY like an engine knock(ask me how I know-dont ask me how long it took to nail that noise down and how many times I had that engine out and torn down, LOL).
 

mavgrab302

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No the crank bearings thrust washers rod journals wrist pin everything was within spec or new. I actually found out what it was yesterday by a process of elimination manually running the motor with the piston and cylinder off with the engine cases on and seeing if I was getting oil flow The oil squirter was stopped up. So unknowingly I actually helped Carrillo with this issue that’s happened a few times with this quad. Which might lead me into a little bit of money if I can mock up and 3-D print a prototype oil rail instead of just one singular squirter. I guess nobody has tested this because this particular four wheeler has a oil pressure valve below the cylinder that lets oil back into the case cavity that holds the oil so it’s kind of tough to test But that’s what it ended up being. but that’s what it ended up being
 

mavgrab302

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I tell you though it sure makes me hate honda. I never felt defeated before this damn thing. These bikes had huge issues back in 04-05 with cranks failing..Anyways while it is much quieter the knock has returned after a night of riding. So going to strip it all down for the third time. Just so many bad ideas on this engine from it only holding .8 qts of oil, one piston jet on a single cyl engine, oil relief valve and I believe the crank is actually not even centered in bore but offset 1-3mm which is why they shove the piston into the wall. Theyre noisey new but dont leave shavings..so after 5 hours of riding very very little but still bugs me
 
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