2018 rtv-xg850 running like trash at only 125.5 hours

[lugbolt]

seat belt limiters are on all of the major SxS / UTV brands. I assume it's a mandate? (dunno)

they cut ignition and/or fuel injection pulse to one or more cylinders. On some machines the throttle is pulled way back electronically so that you only get maybe 25% power, keeps speed under 15 mph (give or take) if the unit sense forward gear (high or low) and seat belt not connected.

I don't remember if the sidekick uses an ETV (electronic throttle valve). I don't think they do.

excess fuel in the crankcase is not uncommon for machines that idle a lot and/or are used for frequent start/stops.. Oil cant get warm enough to boil off the contaminants that are normally produced by combustion. RPM warms the oil. Some machines use a water cooled oil cooler; which is also an oil heater since coolant warms up much faster than oil does.

 

[truckfixer]

Have you checked that your crankcase isn't overfilled with gas contamination. Seems to be a common problem with them.

yeah it kept getting oil changes

 

[truckfixer]

I keep thinking about how excessive un-burnt fuel ends up in the crank case which also makes me think of an ignition or timing issue.

This seatbelt issue - does the ECU just stop firing one or more of the cylinders to retard the engine while the fuel pumps and injects merrily away into the cylinders forcing the un-burnt fuel to get dumped in the exhaust stroke or squeeze past the rings in the compression stroke?

The ECU is just running software after all...who knows, maybe the ECU software is buggy and got orphaned between Subaru and Kubota when K tried putting a motor designed as a constant speed power unit into a variable speed application. Techs here in N.A. won't be able to diagnose these black box issues when the designer in Japan either gave up, dropped the ball or died during covid. Kubota Japan probably knows there's an issue but doesn't have or doesn't want to allocate the resources to fix the problem.

it's actually cutting both injectors like it does at redline otherwise it would explode the spark arrestor, at least a quad I had did when it cut its coil signal during driving it

 

[truckfixer]

seat belt limiters are on all of the major SxS / UTV brands. I assume it's a mandate? (dunno)

they cut ignition and/or fuel injection pulse to one or more cylinders. On some machines the throttle is pulled way back electronically so that you only get maybe 25% power, keeps speed under 15 mph (give or take) if the unit sense forward gear (high or low) and seat belt not connected.

I don't remember if the sidekick uses an ETV (electronic throttle valve). I don't think they do.

excess fuel in the crankcase is not uncommon for machines that idle a lot and/or are used for frequent start/stops.. Oil cant get warm enough to boil off the contaminants that are normally produced by combustion. RPM warms the oil. Some machines use a water cooled oil cooler; which is also an oil heater since coolant warms up much faster than oil does.

this one never idled for more than 5 minutes at a time but always would heat up in ~1 minute which isn't normal to my knowledge, my understanding is that the engine piston rings is a poor design based on how much oil it burned

 

[Torinodan]

Verify your plugs are properly gapped and then try a heat range or two hotter. Had one come through that had the wrong plugs in it. Plugs too cold.

 

[truckfixer]

Verify your plugs are properly gapped and then try a heat range or two hotter. Had one come through that had the wrong plugs in it. Plugs too cold.

first thing i checked just forgot to mention since at 125 hours they were perfectly fine, plugs are thr correct range and new ones changed nothing. choking the engine fully with a hand changes its running condition until the ecm adjusts

 

[lugbolt]

this one never idled for more than 5 minutes at a time but always would heat up in ~1 minute which isn't normal to my knowledge, my understanding is that the engine piston rings is a poor design based on how much oil it burned

define "heats up".

Engine oil does NOT have a temperature gauge anywhere, and to my knowledge is not even logged in the ECU, only coolant temp-which is totally different. Coolant temp can be 200 degrees but oil temp might still be 75 deg. Takes a LOT longer to warm the oil than coolant, and the oil temp needs to be 200+ for a good while to boil off contaminants.

if you think the rings are leaking, do a leakdown test and verify it. Then you know for sure.

"bad design". Explain. And where did you get that information from?

 

[truckfixer]

define "heats up".

Engine oil does NOT have a temperature gauge anywhere, and to my knowledge is not even logged in the ECU, only coolant temp-which is totally different. Coolant temp can be 200 degrees but oil temp might still be 75 deg. Takes a LOT longer to warm the oil than coolant, and the oil temp needs to be 200+ for a good while to boil off contaminants.

if you think the rings are leaking, do a leakdown test and verify it. Then you know for sure.

"bad design". Explain. And where did you get that information from?

coolant temp. rings from a friend's torn down engine (snapped crank because he tried to jump it) were weirdly thin and just not super well supported for scraping type oil control rings, I'm sure they work well at a single rpm but varying the rpm makes them not evacuate oil effectively it did pass a leakdown since its a fueling issue as confirmed by closing the intake tube off makes it run alot better, but injectors are clean and functional

 

[lugbolt]

coolant temp. rings from a friend's torn down engine (snapped crank because he tried to jump it) were weirdly thin and just not super well supported for scraping type oil control rings, I'm sure they work well at a single rpm but varying the rpm makes them not evacuate oil effectively it did pass a leakdown since its a fueling issue as confirmed by closing the intake tube off makes it run alot better, but injectors are clean and functional

ring thickness alone is meaningless. I have, still do, and will continue to use ring thickness to my advantage, just exactly the same as automotive manufacturers do. Back in the day, 5/64 rings were normal, big thick, heavy, and power robbing things. Hi-performance rings were 1/16-1/16-3/16. Then OMG the super stock guys were using 2mm rings, then 1.5, then 1.0mm, now they're getting them closer and closer to 0.5mm compression rings and 1.2 mm oil rings-if there is an oil ring (some guys are only using 2 rings per cylinder). The clearance between the ring and the ring groove is what's important, and just as important is the finish of the cylinder wall. But ring thickness alone is meaningless without knowing everything else.

The thin rings also break in quickly, but they are also VERY sensitive to dirt; IOW they wear out much faster if the engine is "dusted" even the least bit. Cylinders have gone almost exclusively to chrome liners (aluminum with a "sprayed on" coating of another alloy in the bore). This coating is pretty resiliiant but it's not intolerant of contamination. Basically the tech is nice, and it works, but the sensitivities to certain things have greatly increased the need for proper operation and proper maintenance. We don't want to do any of that since we just want to use our equipment. I'm guilty.

 

[truckfixer]

ring thickness alone is meaningless. I have, still do, and will continue to use ring thickness to my advantage, just exactly the same as automotive manufacturers do. Back in the day, 5/64 rings were normal, big thick, heavy, and power robbing things. Hi-performance rings were 1/16-1/16-3/16. Then OMG the super stock guys were using 2mm rings, then 1.5, then 1.0mm, now they're getting them closer and closer to 0.5mm compression rings and 1.2 mm oil rings-if there is an oil ring (some guys are only using 2 rings per cylinder). The clearance between the ring and the ring groove is what's important, and just as important is the finish of the cylinder wall. But ring thickness alone is meaningless without knowing everything else.

The thin rings also break in quickly, but they are also VERY sensitive to dirt; IOW they wear out much faster if the engine is "dusted" even the least bit. Cylinders have gone almost exclusively to chrome liners (aluminum with a "sprayed on" coating of another alloy in the bore). This coating is pretty resiliiant but it's not intolerant of contamination. Basically the tech is nice, and it works, but the sensitivities to certain things have greatly increased the need for proper operation and proper maintenance. We don't want to do any of that since we just want to use our equipment. I'm guilty.

the real problem is that the air system on these at some point (at least both of ours at very different times of the run of subaru motors that use honda African twin starters ) decide to bypass the filters entirely somehow and suck in dirt. his cylinders are also entirely gouged up from the poorly designed oil rings trapping contamination and they look to have been flexing in their grooves i know his made it to 300 hours but I'm wondering if mine will even get to 200 now based on what's already going wrong, his is getting a 670 v twin swap so it's a functional thing again

 

[Sidekick]

the real problem is that the air system on these at some point (at least both of ours at very different times of the run of subaru motors that use honda African twin starters ) decide to bypass the filters entirely somehow and suck in dirt. his cylinders are also entirely gouged up from the poorly designed oil rings trapping contamination and they look to have been flexing in their grooves i know his made it to 300 hours but I'm wondering if mine will even get to 200 now based on what's already going wrong, his is getting a 670 v twin swap so it's a functional thing again

If someone is doing an engine swap on a Sidekick, It would be nice if they document it because sounds like many will eventually need a replacement. Would be nice to have a more reliable option other then another $5k in a Subaru engine with the same problem. It would make a good thread on here even.

 

[lugbolt]

the real problem is that the air system on these at some point decide to bypass the filters entirely somehow

this will happen when the filter is neglected. Gotta maintain them, and properly. The location of the filter is not ideal, and it gets dirty quickly, so you have to keep an eye on them-often. Other manufacturers specifically design their air intake system such that the filters and intake system don't get that dirty nor nearly as quickly. This is one reason I have always said that Kubota's entrance into the sice-by-side market really needed a LOT more R&D.

also on air filters. They'll often "look" clean from the outside. Pull it out, tap it and if you see dirt falling out, replace it. Do not clean paper air filters, throw them out and replace them. It might cost you, but so does a new Subaru engine and I can almost guarantee that spending $40 or whatever on a filter is a whole lot less intrusive than spending $5000+ on a new engine. BUT-for some odd reason, people often tend to remember (and cuss) the cost of a a filter and/or oil, and often cheap out for aftermarket stuff, so they don't have to go to the "stealership" and get "bent over". I buy Ford parts at the dealer, Polaris parts at the dealer, Yamaha parts at the dealer-and I try to use as much OEM stuff as possible, including filters and fluids. after all, it IS designed specifically for the vehicle.

 

[truckfixer]

this will happen when the filter is neglected. Gotta maintain them, and properly. The location of the filter is not ideal, and it gets dirty quickly, so you have to keep an eye on them-often. Other manufacturers specifically design their air intake system such that the filters and intake system don't get that dirty nor nearly as quickly. This is one reason I have always said that Kubota's entrance into the sice-by-side market really needed a LOT more R&D.

also on air filters. They'll often "look" clean from the outside. Pull it out, tap it and if you see dirt falling out, replace it. Do not clean paper air filters, throw them out and replace them. It might cost you, but so does a new Subaru engine and I can almost guarantee that spending $40 or whatever on a filter is a whole lot less intrusive than spending $5000+ on a new engine. BUT-for some odd reason, people often tend to remember (and cuss) the cost of a a filter and/or oil, and often cheap out for aftermarket stuff, so they don't have to go to the "stealership" and get "bent over". I buy Ford parts at the dealer, Polaris parts at the dealer, Yamaha parts at the dealer-and I try to use as much OEM stuff as possible, including filters and fluids. after all, it IS designed specifically for the vehicle.

see that's just it. it was a new filter but the rubber tube seal is weaker than the suction needed for the filter

 

[truckfixer]

If someone is doing an engine swap on a Sidekick, It would be nice if they document it because sounds like many will eventually need a replacement. Would be nice to have a more reliable option other then another $5k in a Subaru engine with the same problem. It would make a good thread on here even.

I don't think you do, the entire harness is getting gutted so no speedo or anything but basically hardwired power to p/s, lift back and essential systems, and a toggle switch pump for the carb plus whatever jank is going to happen for the torque converter
it's basically going to be a more complicated 90s kawasaki mule with maybe more power