Calling all engine builders/gurus/enthusiasts

[wnelax04sr5]

So i just rebuilt a 42ci, 700cc, polaris atv motor. It had bad rod knock on one of the connecting rods, and the rebuild consisted of new crank, rods, rings, bearings, valve seats and guides, and all the other accoutrement of an engine rebuild. Everything was put back together with new gaskets, torqued to factory spec with the correct thread locker, and reinstalled in the vehicle. the motor started immediately and idled very well after initial startup before it was shut down to finish the installation.

Since completing the rebuild and install, its been run up to temperature, varying rpms per break in procedure, however, it had not been under any load, just sitting and revving or driving around at moderate throttle on flat ground. Yesterday it went on its maiden voyage after about 1 hour of break in, and whenever it was under load it burnt oil, bad. lots of smoke out the exhaust, most of which came when riding up hills, but the smoke persisted even after the terrain leveled out. after about 1 hour of riding, it stopped smoking pretty much altogether, with just a faint smell of burnt oil coming out the exhaust.

fast forward to today, after being parked all night, i checked the oil level, and of the two quart capacity, it appears to have lost at least a 1/3 of that.

my question is, i know rings need time to seat, and some engines burn oil after rebuild, but is this amount normal? i planned on topping it off and riding again to see whether it happened again, but also don't want to be pushing a motor thats ripping through oil. i greatly appreciate any feedback on this, the atv is my fathers and getting it rebuilt and back together was a christmas present for him, so i want it to be right.

thanks in advance

 

[Gray trdpro]

You didnt say if you honned the cylinders. The rings need fresh walls for the rings to seat.

 

[wnelax04sr5]

You didnt say if you honned the cylinders. The rings need fresh walls for the rings to seat.

cylinders were honed

 

[02SE]

I'd say the oil usage sounds excessive. But there are too many unknowns to say if the rate of oil usage is acceptable, or if it will slow down or stop.

Was the bore honed with the appropriate finish for the rings used??
What rings were used?
What is the ring gap?
Were the rings positioned correctly?
What is the bore-to-piston clearance?
Did the head and block have the correct RA for the headgasket used?
Was the headgasket torqued correctly?
Were new headbolts/studs used?
What is the valve guide clearance?
Were new valve stem seals used?
What oil viscosity is being used?
Etc., etc.

At this point I'd run it, and see if the oil usage decreases.

 

[wnelax04sr5]

I'd say the oil usage sounds excessive. But there are too many unknowns to say if the rate of oil usage is acceptable, or if it will slow down or stop.

Was the bore honed with the appropriate finish for the rings used??
What rings were used?
What is the ring gap?
Were the rings positioned correctly?
What is the bore-to-piston clearance?
Did the head and block have the correct RA for the headgasket used?
Was the headgasket torqued correctly?
Were new headbolts/studs used?
What is the valve guide clearance?
Were new valve stem seals used?
What oil viscosity is being used?
Etc., etc.

At this point I'd run it, and see if the oil usage decreases.

to clarify, oil usage had stopped mid break in. however its been below 15* here and i haven't had a chance to refill and see if it continues.

to answer your questions to the best of my ability, cylinders and head were done by a machine shop. honed both and the head was rebuilt with new seals, clearances set at the machine shop. the rings are brand new oem, positioned correctly upon installation. the head was torqued to the correct spec in the correct pattern, with a new head gasket. i don't have the ring gap near me right now, the rings however come set with the correct gap for the pistons, and did not need to be oversized because no material was taken out of the cylinder walls.

 

[02SE]

Well, if the oil usage has stopped, then you should be good to go.

Also to clarify there are several different types of rings. Some of which can contribute to a quicker break-in.

I have not rebuilt a Polaris engine, so I'm not aware of what specific type of ring they use as OEM.

But there are still so many unknown variables, that a definitive answer, or even an educated guess as to what would be considered normal for THIS rebuilt engine, is impossible to say.

Just an example: Many OEM's these days are using low-tension rings to reduce frictional losses, thus improving fuel consumption. Sometimes they get it wrong, and end up with lots of oil burning engines.

Camry's of the recent past have been prone to using excess oil because of this.

In the Powersport industry, the BMW Boxer Twin was already prone to excess oil usage due to it's engine layout. Newer low-tension rings, and a lower viscosity spec oil in recent models, has made them even more prone for excess oil usage.

At any rate, I hope your ATV runs good from here on out.

 

[BlackWorksInc]

Well, if the oil usage has stopped, then you should be good to go.

Also to clarify there are several different types of rings. Some of which can contribute to a quicker break-in.

I have not rebuilt a Polaris engine, so I'm not aware of what specific type of ring they use as OEM.

But there are still so many unknown variables, that a definitive answer, or even an educated guess as to what would be considered normal for THIS rebuilt engine, is impossible to say.

Just an example: Many OEM's these days are using low-tension rings to reduce frictional losses, thus improving fuel consumption. Sometimes they get it wrong, and end up with lots of oil burning engines.

Camry's of the recent past have been prone to using excess oil because of this.

In the Powersport industry, the BMW Boxer Twin was already prone to excess oil usage due to it's engine layout. Newer low-tension rings, and a lower viscosity spec oil in recent models, has made them even more prone for excess oil usage.

At any rate, I hope your ATV runs good from here on out.

I'm guessing the "one piece" design of the oil control rings is what you mean by Low Tension? So far a lot of manufacturers have been using these one-piece rings vs. the traditional 3-part ones and have been having oil consumption issues as a result (ironically the "fix" is installing 3 part rings.)

 

[02SE]

I'm guessing the "one piece" design of the oil control rings is what you mean by Low Tension? So far a lot of manufacturers have been using these one-piece rings vs. the traditional 3-part ones and have been having oil consumption issues as a result (ironically the "fix" is installing 3 part rings.)

Well, there are several aspects to consider in ring design, that affect ring tension.

Tangential tension, ring thickness, and unit pressure, are some of the considerations.

One-piece vs three-piece isn't really the determining factor. The three-piece "fix" is just a band-aid for what was an inadequate design initially.

Being a Toyota Tech, have you had to fix any of those late-model Camry oil burners?

 

[wnelax04sr5]

Well, if the oil usage has stopped, then you should be good to go.

Also to clarify there are several different types of rings. Some of which can contribute to a quicker break-in.

I have not rebuilt a Polaris engine, so I'm not aware of what specific type of ring they use as OEM.

But there are still so many unknown variables, that a definitive answer, or even an educated guess as to what would be considered normal for THIS rebuilt engine, is impossible to say.

Just an example: Many OEM's these days are using low-tension rings to reduce frictional losses, thus improving fuel consumption. Sometimes they get it wrong, and end up with lots of oil burning engines.

Camry's of the recent past have been prone to using excess oil because of this.

In the Powersport industry, the BMW Boxer Twin was already prone to excess oil usage due to it's engine layout. Newer low-tension rings, and a lower viscosity spec oil in recent models, has made them even more prone for excess oil usage.

At any rate, I hope your ATV runs good from here on out.

thanks for the help/advice, after a little digging i can't find the tensions of the stock three piece rings, ill be doing a compression test to try and rule out potential causes today or tomorrow.

 

[KidVermicious]

thanks for the help/advice, after a little digging i can't find the tensions of the stock three piece rings, ill be doing a compression test to try and rule out potential causes today or tomorrow.

I'm not near as smart as the other two guys in this thread, but that's what I was going to suggest. Make sure you've got a problem before you chase it.

 

[cashmoney]

Go to a Polaris forum and ask them. More than likely they'll know more about it than anyone here.

 

[wnelax04sr5]

Go to a Polaris forum and ask them. More than likely they'll know more about it than anyone here.

i already have. most replies consisted of "take it to the dealer" or "just buy a new one"

i was hoping for better, and thus returned to my homeland of t4r to seek better advice

 

[02SE]

thanks for the help/advice, after a little digging i can't find the tensions of the stock three piece rings, ill be doing a compression test to try and rule out potential causes today or tomorrow.

I should have been more specific. If the excess oil usage has stopped as you said, then I'd suggest not worrying about it.

The rings aren't the only determining factor in excess oil usage anyway.

As Kidv said: "Make sure you've got a problem before you chase it".

 

[BlackWorksInc]

Well, there are several aspects to consider in ring design, that affect ring tension.

Tangential tension, ring thickness, and unit pressure, are some of the considerations.

One-piece vs three-piece isn't really the determining factor. The three-piece "fix" is just a band-aid for what was an inadequate design initially.

Being a Toyota Tech, have you had to fix any of those late-model Camry oil burners?

Not me personally, I'm the fast guy for dashes. Got a couple guys who do those oil consumption engines fast, seen enough apart to know what you mean; though all the "low tension" rings I've seen including pictures from my friend in Seattle's shop and such have been one piece designs with a spring. The fix for the Toyota 2AZ-FEs has been a new ring and piston set with 3 part oil control rings like you'd normally see back in the day.

 

[wnelax04sr5]

I should have been more specific. If the excess oil usage has stopped as you said, then I'd suggest not worrying about it.

The rings aren't the only determining factor in excess oil usage anyway.

As Kidv said: "Make sure you've got a problem before you chase it".

I'm aware, just wanting to go through a motor i spent quite a bit of time/money rebuilding and rule everything out