Honda ATV Forum banner

21 - 40 of 47 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter #21
Yes I did run it with the vent removed running into a water bottle and it almost filled the bottle before I shut it down, dropped the head off with a local machinist today waiting to here back if it checks out good I'm gonna check all the screens and oil pump I will keep everyone updated since this problem has already stumped 4 good small engine mechanics prior I am excited to figure out this gremlin and get er back to runnin tip top since the machine is absolutely mint besides this oil issue!
 

·
Premium Member
Joined
·
12,554 Posts
Yes I did run it with the vent removed running into a water bottle and it almost filled the bottle before I shut it down, dropped the head off with a local machinist today waiting to here back if it checks out good I'm gonna check all the screens and oil pump I will keep everyone updated since this problem has already stumped 4 good small engine mechanics prior I am excited to figure out this gremlin and get er back to runnin tip top since the machine is absolutely mint besides this oil issue!
I think maybe you should have dropped off the jug and piston
 

·
Super Moderator
Joined
·
5,956 Posts
Check that the connecting rod isn't bent too. If the motor ever got sunk and hydro-locked, the rod will bend and deflect to one side, which cocks and twists and binds the piston in the bore as it moves through its stroke. Piston rings can't handle any instabilities going on.... they'll pass combustion pressure. A bent rod can be very difficult to spot too.
 

·
Super Moderator
Joined
·
5,956 Posts
Also advise your machinist that a valve seat may have loosened up in the head casting, that happens occasionally on the 350 motors. They can be difficult to notice when you take the head off... but can be following the valve open as the motor is running. They'll generally make some noise though...
 

·
Registered
Joined
·
19 Posts
Discussion Starter #27
Everything checked out good with the entire top end although the machinist said it appeared the cylinder got pretty hot at one point but not enough to compromise the integrity of the cylinder/piston/rings. I'm thinking this all began with something disrupting the oil flow of the engine such as plugged passages/screens and/or a bad oil pump so now that I know the top end is good I'm pulling the bottom end and going through this entire engine to get to the bottom of this so things are about to get much more interesting I'm thinking haha I will keep you all posted on my findings over the next few days!
 

·
Registered
Joined
·
67 Posts
I don't know 350 Rancher motors in particular but if bottom is still in frame you can unhook return line and run to clear bottle
Kick it over a few times to make sure its pumping return oil
That will tell you if screens in sump are plugged/scavenger pump burnt out

Another thing to check is the cranckcase vent
As a wrench your familar with automotive PVC valves
Some bikes havea timed gear driven crankcase vent in them (HD)
If it has a vent like that make sure it's timed right

Other than those two issues the only other reason to pump oil out vent is excessive crankcase pressure
Just gotta see where its coming from

P.S. A burnt or bent valve would have blow by in exhaust or intake but not crankcase
You got a problem with the piston/rod or scavenger pump
RemMax
 

·
Super Moderator
Joined
·
5,956 Posts
This is an intriguing issue and I'm glad you are going after it! I'm sitting here wondering if oil spray is directed toward the vent area in the case from some sort of bad leak, be it a blown o-ring seal or a cracked or porous case... or similar fault? There is way too much oil being passed to be easily explained, since the topend checked out fine. Got my Popcorn and standing by....
 

·
Registered
Joined
·
19 Posts
Discussion Starter #30
The connecting rod is tight straight and true this atv has never been hydro-locked I am second owner and the original owner was an old man who used it to drive down gravel roads around his cabin it has never been road hard nor put away wet haha easily can tell by the age and its condition. Whatever is causing this condition does not appear to have been provoked by the operators misuse in anyway if I had to guess, but who knows he could have rarely changed the oil or ran it low on oil or something of that nature he is not a mechanically inclined fella from what he told me. BTW thanks for the link to the service manual Retro! Will come in very handy!
 

·
Registered
Joined
·
19 Posts
Discussion Starter #32
Well had to order a flywheel puller so been waitin on that till today I got the cases split and so far tonight all I found was the oil strainer in the bottom of the crankcase was partially plugged up with debris although I don't think bad enough to cause it to find another path out like through the breather. Another thing Im thinking I will do after I thoroughly inspect and clean the oil passages is install a new timing chain just thinking this one could be pretty stretched by the looks of it possibly so it can't hurt to eliminate that also I have yet to inspect the tolerances on the oil pump which will be done soon. Something has to be causing resistance to the oil flow causing it to take another path right out into the damn airbox but thinking that also if the timing chain is out of spec that will throw it out of time ever so slightly but maybe enough where it's causing a valve to slightly open enough where it's causing the crankcase to pressurize enough to blow the oil out the breather
 

·
Super Moderator
Joined
·
5,956 Posts
Is there any sort of baffle next to the crankcase vent exit? Were all of the screens in place (must be 3 of them, aren't there?) between the case halves?
 

·
Premium Member
Joined
·
6,515 Posts
Well had to order a flywheel puller so been waitin on that till today I got the cases split and so far tonight all I found was the oil strainer in the bottom of the crankcase was partially plugged up with debris although I don't think bad enough to cause it to find another path out like through the breather. Another thing Im thinking I will do after I thoroughly inspect and clean the oil passages is install a new timing chain just thinking this one could be pretty stretched by the looks of it possibly so it can't hurt to eliminate that also I have yet to inspect the tolerances on the oil pump which will be done soon. Something has to be causing resistance to the oil flow causing it to take another path right out into the damn airbox but thinking that also if the timing chain is out of spec that will throw it out of time ever so slightly but maybe enough where it's causing a valve to slightly open enough where it's causing the crankcase to pressurize enough to blow the oil out the breather
I would certainly replace the timing chain while you're in there, but I went through my neighbors bottom end, cleaned everything out well, and put a new timing chain on it. It still burped oil into the airbox.
 

·
Registered
Joined
·
19 Posts
Discussion Starter #35
No baffle anywhere next to the crankcase vent exit, 2 oil strainers and both in place one was partially covered with debris cleaned it up and inspecting and thoroughly cleaning the rest of the crankcase no definitive solutions as of now
 

·
Registered
Joined
·
19 Posts
Discussion Starter #37
this entire engine will be new when it goes back together cuz I'll be damned if I tore it completely down and fixed nothing haha
 

·
Registered
Joined
·
19 Posts
Discussion Starter #38
Lil update on this problem finally got parts and got er back together problem appears to be fixed! It was either the timing chain or the partially plugged oil strainer in the bottom of the crankcase, timing chain appeared a little stretched so I replaced it. Cleaned and inspected all oil passages and oil cooler but nothing was obviously plugged up. Put a new complete engine gasket, o ring, and oil seal kit in engine also and she purrs like a kitten without spittin oil
 

·
Super Moderator
Joined
·
5,956 Posts
Sweet! Congrats on the thorough assembly & fix! Thanks for keeping us in the loop!

I'll go with clogged scavenge oil strainer being the culprit if limited to just those two choices. Worn out Cam chain can't do that unless it were throwing oil at the vent as it stretched out. But that strainer can not explain Jeeps experience with oil in the airbox unless the scavenge pump were weakened or worn previously maybe? You put eyeballs on everything... Whaddya think?
 

·
Registered
Joined
·
19 Posts
Discussion Starter #40
Scavenge pump checked out within spec and everything else inside the engine looked like new one thing I did notice was before I ever took the bottom end apart I had the valve cover off I turned the engine over to check operation of the valves after setting lash and didn't notice oil coming into valve cover ever and now after doing it when she cranks with the cover off she makes one hell of a mess lol one other thing I forgot to mention was I replaced the oil filter also. Should be good as new now!
 
21 - 40 of 47 Posts
Top