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Discussion Starter #1
Okay so I just swapped my 04 rancher to 4x4. Today I went out to test the 4x4 (works great btw :D). I drove it for maybe an hour and then I checked the airbox, full of oil... Drained it, filled the motor back up to just below the upper line on dipstick, then went and rode it for another hour. Got back, check the oil. None on stick, all in breather box. There was also water in oil but I can't figure out where it came in. It's no grit in it tho, just iced coffee colored oil
 

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Hum....likely swallowed some water over pressurizing the engine and/or you are now getting blow by via pressure getting past the rings. You have caused some ring damage.
 

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I think your 2004 350 is made just like my 2002 450 , there is a crankcase vent tube that runs to the air box , that hose is thin and soft quality hose and it was was all cracked up at the connection when I got the bike , ------- I'd check that hose out
 

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Discussion Starter #4
That hose is in perfect condition. My bike has needed rings for 2 years now. I have the rebuild kit being shipped right now, but even before it has never done this. I have no idea where it would swallow water from though. The air box itself was never even submerged, maybe got water above the tires but that's it
 

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Discussion Starter #5
Any special tricks to figure out where it's taking in water?
 

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Any special tricks to figure out where it's taking in water?
if you got water above your tires ?, then i'd bet the drain tube hole in the breather box is open ?, is the tube plug on the bottom of the air box ??. if not ?, then that's how water is getting into the air box and motor.
 

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you need to check all your crank case vent tubes, see if they are cracked ?, not on tight ?.
 

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The neighbor's 350 I'm working on burps oil into the air box too.

I tore it down, cleaned out the bottom end, but on the top end I just honed it and put new rings in it. Figured if it worked, great. If not, not a big deal to take the top end back off and have it machined.

Supposedly some of these 350's will burp oil out if you run it with the dipstick showing full, but do fine with an oil level 1/2 way up the dipstick.

Having problems with the carb float leaking on this one too. Cleaned the carb and put a kit in it, and still leaks.

I'm torn between trying this (probably Chinese) set out or going G&H on the top end.

Cylinder Piston Gasket Top End Rebuild Kit For 2000-2006 Honda Rancher TRX350 | eBay

Undoubtedly G&H would be what I would do were it mine, but my neighbor is a tightwad, so he'll probably cringe at spending twice as much. Anyone tried these aftermarket cylinders?

Same with the carb. I've had good luck with Chinese carbs for some small Honda generator (GX) motors, but I'm betting the $40 350 carbs will be junk.
 

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Discussion Starter #9
As far as I know there's only one crankcase vent, on the right side of the motor behind the heat shield running into airbox, right? That vent line is fine.
My bike will burp out the oil until there's no oil touching the dipstick anymore...
I've flushed the motor and changed the oil but it's still doing this.
 

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Discussion Starter #10
Any special tricks to figure out where it's taking in water?
if you got water above your tires ?, then i'd bet the drain tube hole in the breather box is open ?, is the tube plug on the bottom of the air box ??. if not ?, then that's how water is getting into the air box and motor.

The water isn't coming through the airbox though. All the oil in the airbox was free of water. The bike never lost any power or anything. I would've never known anything was wrong if I had not decided to check the airbox
 

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Yeah, that's your piston getting pressure blowing past it into the bottom of the motor, and that pressure pushes the oil out of the crankcase into the airbox.

From what I've seen, only fix is to rebuild your top end.

I do find it strange that yours didn't do it before.

My neighbor's bike has new rings, but again, I just honed it, so probably needs to be bored out. I just find it weird that this bike has the burping oil into the crankcase but don't have any smoke/oil coming out of the exhaust.
 

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Discussion Starter #12
My top end rebuild kit (includes brand new cylinder) is estimated to arrive tomorrow. So when I rebuild it, it should stop?

Also, could water get in through bad gaskets on the top end? My cylinder has recently slowly become covered in a black, oil like gunk. Could this be a bad gasket on the cyclinder and could this be where water entered the motor?
 

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Discussion Starter #13
Because I've had the entire motor submerged before (before the "black gunk" started) and i had no problems. And I have not done anything to the motor since other than changed the front crankcase cover. But the new cover is on tight so that can't be where the water entered.
 

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My top end rebuild kit (includes brand new cylinder) is estimated to arrive tomorrow. So when I rebuild it, it should stop?

Also, could water get in through bad gaskets on the top end? My cylinder has recently slowly become covered in a black, oil like gunk. Could this be a bad gasket on the cyclinder and could this be where water entered the motor?
Should stop then. What kind of top end kit did you get? OEM or one of the ebay kits? (I'm asking because it looks like my neighbor is going to need a top end)

Because I've had the entire motor submerged before (before the "black gunk" started) and i had no problems. And I have not done anything to the motor since other than changed the front crankcase cover. But the new cover is on tight so that can't be where the water entered.

You have lots of potential places for water to get in. Crank seal, shifter seal, front and rear output seals, crankcase vent.

Since you just replaced your front cover, did you put a new front output seal in the cover when you installed it? Did you use a new gasket or Hondabond on the front cover? Any oil leaking out up there?
 

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Discussion Starter #15 (Edited)
No I did not use any kind of sealer when I put the cover on. I just put it on and torqued the bolts to +/- 25 lbs to where they felt like they weren't gonna break but they were right enough to make a good seal. It didn't appear as if any kind of sealant was used to install the front case and it doesn't say to use any sealant in the manual so I figured I would be fine. The swingarm boot is brand new so I don't see how water would enter through there. The front output seal seems fine, I inspected all the bearings and seals in the new case before I installed it. I feel like the water entered through the head gasket, it was letting oil see through (black gunk on cylinder) and when I pulled the head, there was a puddle of oil under the gasket. The rings seemed to be fine, although the piston had some pretty deep scratches in the side that was scaring the cylinder.


I bought an eBay kit for $114. The seller was first.racing. The kit includes brand new cylinder,piston,wrist pin, circlips, rings, gaskets, and a brand new NGK plug. The parts seem to be of good quality. I haven't side by side compared yet, but I think the new cylinder is actually heavier than the OEM one. The cylinder bore surface seems questionable, but I am inexperienced with what would be acceptable so I took plenty of pictures.In the photos you will see what looks like dust or sand on the parts, that is just styrofoam from shipping that I haven't cleaned off.


https://imgur.com/gallery/JuJed


As for as putting the kit on, do I need to use any kind of gasket sealer? And the inner bore of the cylinder feels very smooth, all of the visible marks are horizontal, not vertical. Would this cause any problems? and if so could I hone it or what should I do.
 

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I'll wait for shadetree or one if the other more knowledgeable guys to chime in, but I think I'd hone that. Isn't crosshatching supposed to be diamond patterned?

I've looked at those kits and wondered if they were workable or chinese junk. Cheaper to buy that kit new than to bore and go oversize with your old cylinder
 

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Discussion Starter #17
I compared the cross hatch in the new cylinder to what crosshatch was left in the bottom of the old cylinder and they look exactly the same. I think it'll work w/o and honing, but I will wait too to see what shadetree says. I'm not exactly in any hurry to put this kit on, it's freezing outside and I still have to go get some diesel to flush motor, and order valve cover gasket, exhaust gasket, and intake o-ring
 

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Discussion Starter #18
Okay so today i priced valve cover gasket. The cheapest way to do it is still gonna cost 30$ with everything else I've got to order, but I could get the other gaskets for 15. (yes I'm cheap) Could I get say with using permatex high temp gasket maker on the valve cover?
 
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