[shadetree]

To take all guesses out of the situation pull it apart and measure your piston to bore clearance, measure to see if the bore is out of round.

btw, you wont get a good gauge at whether or not your valves are leaking with oil, your best bet is using carb clean, brake clean, or even gas, dump it in the intake and exhaust ports and see if it seeps through.

My bet is the bore is out of round. even though its new, it should not consume that heavily.

Will try with regular unleaded tonight. But i'm now thinking the cylinder as well. If I had to guess something is up with the cylinder, the compression rings have enough pressure to seal up or meet the imperfection, but the oil ring does not and it is leaving a film of oil on the cylinder wall. That would explain the good compression, and no draw down on the oil I put in the cylinder last night, but still having some blow by during the compression stroke. On that note though, wouldn't the compression rings be tight enough against the cylinder to scrape the oil off?

nope, the oil rings keep the oil off the cylinder wall, they have nothing to do with the compression.

 

[shadetree]

in other words, if your oil rings are bad ?, they will let oil slip by, and bleed out the exhaust, the compression rings will not stop oil from getting by, this is why your getting a smoking engine.

 

[Jeepwm69]

welllllllllllllll...lol, first..yes..chit happens !. but if a person takes their time, uses the correct parts ( or just makes sure parts will work ? ), then you worry about if your work was done right ?. I've been down the same road as the OP many times !, it sucks to rebuild something, and it not run right ?, or something else pops up, that you had no clue there was a problem, or what caused it ?, until you discover it !..lol. had this problem on an old trx350 rancher many moons ago, damn thing ate my lunch and some !..lol. little did I know, that the valve seat could work it's way out of the head once warm/hot ?. I replaced almost everything new with oem, and it still made a rattle when warm/hot ?..that's when I looked into this matter deeper, and found out Honda had a defective head on some of their trx350 rancher heads !..lol.

Interesting and good to know.

The Rancher I've been rebuilding for my neighbor runs good now. It quit burping oil into the airbox (rings must have seated), carb quit leaking with a new float needle, and the disc brakes from a 420 Rancher stop it great.

It rattles like hell though, and I adjusted the valves before I ever tried to crank it.

He got a parts bike with this one, so maybe I'll swap the heads and see if it helps.

if the cam chain is good ?, and valves are set right ?, i'll bank on the valve seat coming out when it's warmed up !..lol. I know this for a fact !. I replaced cam, cam chain, valves were good as far as valve clearance , and it started up great, but once it got warmed up ?, i'd hear what sounded like a bad cam ?, bad cam chain ?, replaced all of that with new oem, still did the same thing. well, after it did it again, I shut it down, pulled the head, and after closely looking at the valve seat under the springs ?, I could see them sticking up ?..asked my bud at my dealership, he says '' oh yeah..those ranchers had a defective head on some of them '' ..now I learned something..lol.

Cam chain is new, valves were cleaned up with new seals, and set to specs.

It was quiet at first. Got loud after a couple of mins of riding it. Stayed loud, so isn't only rattling when hot.

Sorry for the hijack OP.

I had a 420 that did what you have going on. I took the cylinder off, ran a hone through it and put another set of rings in it and it's been fine since.

Not sure if I got a bad ring or what. I threw parts at it till it quit smoking (not recommended)

 

[lowbudget]

I was about to throw more parts at it by ordering a new piston and rings at .25 over and have it re-bored, but i'm going to take it to a second machine shop which specializes in atv and outboard motors and have them check the cylinder out. Will report back.

 

[lowbudget]

Went into the shop last night after work, the exhaust port was still full of oil with no leakage, same for the cylinder. I've pulled the jug and cylinder and my brother is dropping it off at the machine shop this morning for a bore measurement. Will see what comes of it.

 

[alloutdoors]

Went into the shop last night after work, the exhaust port was still full of oil with no leakage, same for the cylinder. I've pulled the jug and cylinder and my brother is dropping it off at the machine shop this morning for a bore measurement. Will see what comes of it.

Best of luck. Are you putting it back together or the shop taking a crack at it?

 

[lowbudget]

Went into the shop last night after work, the exhaust port was still full of oil with no leakage, same for the cylinder. I've pulled the jug and cylinder and my brother is dropping it off at the machine shop this morning for a bore measurement. Will see what comes of it.

Best of luck. Are you putting it back together or the shop taking a crack at it?

I'll be putting it back together. The machine shop is just checking the cylinder at this point. I dont have micrometers or bore measuring tools, nor do I feel confident using them if i did own them. So i'm handing that over to a professional. If they tell me its out of round, or scarred, then i'll bore it over. If they say its good, then I'll track down a new head and try that.

 

[Manny]

before you try to replace the head, take it to that machine shop, let them do a full rebuild. or at least cut the seats, 3 angle valve grind, and check the guides.

this is what I do with every rebuild to just cancel out the chance that I would need to tear it down a second time. cheap insurance in my opinion.

 

[HondaGav]

Don't do alot of rebuilds but can these problems be attributed to the oil ring being installed up side down? I know one side of them is rounded and the other sort of cupped to scrape oil off the wall.

 

[shadetree]

Don't do alot of rebuilds but can these problems be attributed to the oil ring being installed up side down? I know one side of them is rounded and the other sort of cupped to scrape oil off the wall.

nope, impossible to install oil rings up side down, the smaller rings will go either way, then you have the center expansion ring, it too will fit on either way, no way of installing them wrong ?..butttttttttt !!!!!!!!!!.it is posb to damage the oil rings when installing the cylinder and piston !..lol.

 

[lowbudget]

Well, machine shop check the cylinder, said one place up top was a smidgen out of round, by just a couple thousandsth. Also said cylinder looked good with no scratches that should affect anything. But he did check my oil ring, it was too small. We pulled the compression rings off and just left the oil rings on the piston and it would pass right through the cylinder barely touching the walls.

I have no idea if this was caused by me grabbing the wrong rings off the work bench, maybe I grabbed my old one. Or by being supplied an out of spec ring. Can not say for sure but knowing me, I probably screwed it up.

Got a new set of rings, put it all together and it fired right up with no smoke. Installed the muffler, and it began smoking as the muffler got hot, just burning off all the old oil inside.

I feel like an idiot for missing something so simple, but its taken care of now, and i'll thoroughly examine my oil rings from this point forward. Lesson Learned.

 

[hodge5]

Well, machine shop check the cylinder, said one place up top was a smidgen out of round, by just a couple thousandsth. Also said cylinder looked good with no scratches that should affect anything. But he did check my oil ring, it was too small. We pulled the compression rings off and just left the oil rings on the piston and it would pass right through the cylinder barely touching the walls.

I have no idea if this was caused by me grabbing the wrong rings off the work bench, maybe I grabbed my old one. Or by being supplied an out of spec ring. Can not say for sure but knowing me, I probably screwed it up.

Got a new set of rings, put it all together and it fired right up with no smoke. Installed the muffler, and it began smoking as the muffler got hot, just burning off all the old oil inside.

I feel like an idiot for missing something so simple, but its taken care of now, and i'll thoroughly examine my oil rings from this point forward. Lesson Learned.

Life is a learning curve. They caught it, your wiser, and you've shared your experience for others to learn from. Could have been a lot worse.

 

[Manny]

hey cheap fix! good to know you didn't have to have it rebored.

 

[lowbudget]

Yep, new $20 set of rings, and I took the old ones off, and placed them on the other side of the shop prior to even opening the new ones. I'm just glad it was cheap and easy, I was not looking forward to buying a new overbore.

 

[mac102004]

What threw me off was I thought you said you had already changed the rings a second time? LOL I was thinking problem with rings but there was no way it would happen twice! haha Glad you got it fixed.

 

[shadetree]

i'd rather toss 20 bucks at a motor, instead of 600 like me !..lmaoo.