It's bad....

[BeartoothBaron]

I'll have to see how the Wossners work out for me, but I think I made the best possible choice. Obviously I have no prior experience with them, but a couple guys who know how to build a motor and ride hard recommended them. The OE piston is probably more tolerant of abuse (especially insufficient warm-up), but the Wossner is lighter, and being forged, likely to stand up to detonation better. I haven't heard of locator pin issues with Wossners, but I'm all ears if they have issues too.

I plan to have the crank trued, most likely by Dan. I couldn't find any other potential trouble with the crank, so I'm hoping it just needs a little massaging; a new PTO bearing wouldn't hurt though. It's only slightly out of spec, and the runout is well in spec, so I'm going to run it the rest of the season, but not going to chance it any longer than that. I'm hoping I can just pull the bottom off, pull the crank assembly, and send that in without having to disturb and replace the top end gaskets (again).

With regard to what caused it, @05rmksteve suggested the fuel filter, and I've got an OE filter on order. Because it's got an AXYS sock filter, and I'd read those should last a long time (never needing replacement, according to some), I didn't think that could be it. The trouble is, I've still got a bog- a little different from what I described earlier - and it would fit with the fuel filter. What it was doing last time I rode it was it'd pull like normal at WOT initially, then bog off after a second or two. Not every time; I backed off immediately and didn't push it after it did it a couple times though. The reason I think that fits with the fuel filter starting to block is because it can pull enough fuel up through mid throttle, but with a burst of WOT it's collapsing the filter, getting what bit of fuel it can from inside the filter, then dropping pressure after a second or two, resulting in a lean bog. If it's been doing that a while, it's almost certainly the cause of the failure. Could be something in that tank of gas blocked the filter, or contributed to the problem. I've got a spare set of injectors I'll clean and check out, then swap in. I'm not sure how I never got a det warning through all of this - if it's leaning enough to cause a significant bog, it's enough to detonate - but the det sensor ohms out. Maybe something to replace anyway. The sled has lots of life left in it, so for however long I keep it, it's worth getting it all squared away. I'm definitely not taking anything for granted anymore though: it's getting regular leakdown and crank runout checks. Meanwhile, my old 600 has to be shaking its head and thinking "seriously bro?"

 

[BeartoothBaron]

Just realized after looking at pictures of the crankcase that the idea of pulling the pistons out the bottom won't work... So it'll be a full engine tear-down. At least I should have my shop closed in this summer, so I'm not (further) cluttering up my garage.

 

[BeartoothBaron]

Bottom line up front: I've got some significant wear on my cylinder walls - will probably need replating before long unless it magically stops - would you even consider changing pistons, or just throw it back together as-is and run it until it gets worse?

Man, I just can't catch a good break on this sled, it seems. Took the engine down in Dec to have the crankshaft done by Indy Specialties (new rod bearings and thrust washers, turned out the rod side clearance was just worn thrust washers). Finally getting it back together (snow this year's been completely demotivating). I noticed some wear in the cylinders when I took it down; I think I should have dug deeper ASAP. Mag side is worse than PTO, but in both cases, you can feel it go from smooth to a discernible amount of roughness as you drag your fingernail across. I contacted both Millennium (who replated it) and Wossner. I was pleasantly surprised to hear back from both. Wossner wasn't helpful (sounded like a form response, basically we'd need to inspect it to say). Jason from Millennium responded that it did look like a problem, but that I could probably run it a bit. He asked about the ring gap, which I shared (.018 top; .022 bottom), and he said it was fine; also said it's probably not worth putting any new parts in it.

I'm scratching my head on this, because it's only got a few-hundred miles, and I was truly meticulous when I did the work. No other signs of trouble: the pistons look perfect except for a few very light score marks, looks like a good piston wash, and the rest of the cylinder walls look perfect. The oil pump is turned up and it's been using oil as expected, plus I've been mixing 100:1 in every tank. The rings do show uneven wear; makes me wonder about the cylinder roundness, but nothing I can do about that. Given the wear in the same spot across both cylinders, I'm leaning toward something off with the pistons/rings; I can't think of anything I did to tweak the rings, I was very careful filing them, deburring, and making sure everything was clean. If there is something wrong with the piston/rings though, I have to wonder if I'd get more out of it running different pistons - not that I'm expecting much, but you never know. I also think too little end gap can be eliminated, but I'll check that again.

Anyway, like I was saying, I'm wondering if anybody's seen this kind of wear and what they did. I plan to run it until it gets worse - checking it over frequently, of course. Eventually, I think I'll pay the (big) price for a pair of OE pistons and probably send the monoblock to @indydan, but given the time and money factor, that probably won't be right away. Just frustrating that my best efforts aren't yielding good results. Also, by the way, I've always been obsessive about warm-up: I start it up on the truck while I put my gear on, and don't move it until I feel heat in the coolers, and won't move it when I stop for a break until I see the temp come up and drop from the thermostat opening. For now, my plan is to put it back together, either with the pistons I've got, or with a cheap set of cast pistons (SPI or ProX, probably), oil it like crazy, baby it, and hope for the best.

 

[BeartoothBaron]

I figure it might be hard to get a good sense of the damage from those photos, so I took another picture up close. I suppose even with that, it's pretty hard to predict how much more I might get out of it (short of someone who works with Nikasil on a daily basis), but any thoughts are appreciated - except from potato farmers.

 

[IDspud]

Oh poo

 

[PSI 800]

go with 2015 or newer stock poo pistons. that is weird looking wear for sure, no idea what would cause that other than something was not right when the cyls were recoated

 

[BeartoothBaron]

OE pistons are what I'm leaning toward down the road, but probably not for now. Not sure I'm up to spending even $650 for a pair of pistons at the moment, and it'd likely be a waste without replating. I thought about going with '15 OE Polaris pistons when I did the top end, but couldn't find them in stock; now they're superseded by the AXYS piston, so most likely they were in transition. Indy Specialty was selling SPI pistons at the time.

Anyway, the one thought that occurs to me is that it could be ring flutter. If it's only occurring near the locating ring, that would explain wear pattern; I don't know for a fact that ring flutter can cause that kind of damage, but it's about the only explanation that makes sense to my mind.

 

[BeartoothBaron]

So I guess I'm leaning towards slapping in a set of cheap cast pistons. For $200, it's not that big a deal if it makes no difference; not to say it couldn't just make things worse, but my gut says that's unlikely. Whatever is going on, it hasn't completely wiped the plating. I'm sure compression will be down a bit, but I could get some miles out of it if I eliminate the cause of the problem.

I'm leaning toward SPI pistons, or maybe ProX. ProX seems more like a brand I could trust, but Dan put out a warning about them several years ago and recommended (and sold some) SPIs. Unless something's changed, it'd probably be SPI. Might just be rearranging the deck chairs on the Titanic, but it gives me something to do...

 

[RHODESIE]

go with 2015 or newer stock poo pistons. that is weird looking wear for sure, no idea what would cause that other than something was not right when the cyls were recoated

those are typical marks that are left behind from wiseco rings. which i believe wossner uses. have seen many engines with those verticle marks and makes no difference in performance.

 

[IDspud]

Your spud farmer discount shows severe ignorance.
One of the best poo motor builders around deals with spuds daily.

 

[KootenayD]

I'm scratching my head on this, because it's only got a few-hundred miles, and I was truly meticulous when I did the work.

I used to feel this way all the time but after a few builds you see where you can move quickly and where you need to slow down and dial in.

It's tough for anyone to say for sure, but I would have a good look at your cylinder specs. Over the years, I've seen some variation in piston dimensions as well (next to none with OE). Worst I ever had was a variation from dome to wrist pin bore that I didn't catch... squish ended up too tight. All the magic happens within a few thou.

Make sure nothing is finding it's way into your intake... maybe a leak down test?

Sure hope you pin this down once and for all.

 

[BeartoothBaron]

those are typical marks that are left behind from wiseco rings. which i believe wossner uses. have seen many engines with those verticle marks and makes no difference in performance.

Yeah, something off with the rings is the only thing that makes sense to me. If the plating was poorly done, I'd think you'd see more random wear patterns, although it could be a combination of the two. Would you consider spending money on OE pistons and running them in the bores as-is?

I'm not sure what to say about Wossner, because some have had really good luck with them. That said, I do remember hearing something about their ring supplier switching at some point. Real bummer if it's a great piston with garbage rings. If the cylinders looked good, I would have put the pistons I've got back in without a second thought.

Your spud farmer discount shows severe ignorance.
One of the best poo motor builders around deals with spuds daily.

Yeah, I just had to poke you back a little! A good farmer has know-how that all the universities in the world couldn't teach.

I used to feel this way all the time but after a few builds you see where you can move quickly and where you need to slow down and dial in.

It's tough for anyone to say for sure, but I would have a good look at your cylinder specs. Over the years, I've seen some variation in piston dimensions as well. Worst I ever had was a variation from dome to wrist pin bore that I didn't catch... squish ended up too tight. All the magic happens within a few thou.

If you have anything gaining access to your intake, you'll want to deal with that. A leak down test wouldn't hurt either.

Sure hope you pin this down once and for all.

I think the intake track is sealed, but I'll definitely pay close attention to that. I did my best to check clearances, but all I had was feeler gauges. Everything was spec'd according to what Wossner calls for (they're set up to drop into the stock bore), and so that's what I told Millennium to hone it to. I've been thinking of buying a bore gauge and fine micrometer; more tools are never a bad investment... I do a lot of stuff most guys would never attempt (like rebuilding the transmission in my truck), and generally get good results, so when something does go sideways, I always want to know what went wrong and what I could have done better. Going back to the original failure, I should have been doing regular leak-down checks - I might have saved myself a lot of time and trouble. Anyway, for now it looks like I'll be trying different pistons and watching it closely. If it holds, it holds; otherwise, it'll probably be a full top-end job with OE pistons. Another $1500, but then the rest of the sled is tip-top. They say better to live with the devil you know...

 

[IDspud]

And meanwhile I was bleeding for you, biting my tongue with so many options to kick you while you’re down….

 

[KootenayD]

Another $1500, but then the rest of the sled is tip-top.

Shhhhhh, your sled is listening!

 

[BBP]

Is it possible that the cylinders weren't clean enough? I wipe the bore with a clean oily rag over & over until there is no residue getting on the rag.

 

[BeartoothBaron]

Well, seems this sled is snakebit. I got it together, running really nice with SPI Hyperdrive pistons, and then yesterday I installed an aftermarket suspension mod and clutch vent, which I strongly recommend against! Maybe it would have been different if I'd speared a genuine Polaris log instead of the aftermarket one... It's a testament to this crummy snow season: I never go out early because I can't afford to be tearing stuff up on a regular basis, but the snowpack is so low you can't take a chance on anything. I did see a lump the log was under and tried to steer around it, but too late. Next thing I know, I'm bucked off, and I hear a split second of grinding followed by sudden silence; it stabbed into the clutch and stopped the engine cold.

Stepping back a bit - I forgot to take a picture, but I noticed something else on the cylinders, a faint square mark opposite the piston pins, maybe a very light four-corner seizure. I bought a bore gauge and micrometer, and one thing I can say is Millennium did a great job. The taper and roundness varied no more than .0005 (tolerance is .002), and the bore is as near 85mm as I can measure. The clearance on the Wossner pistons was .007 and .008. As best I can find, spec is .0048; not sure if something is going on there. The new pistons measure .0046 and .0043 clearance - right in Polaris's tolerances.

With the new pistons, the engine seems to run as strong as ever. I'm nowhere near broken in, so I didn't do any long pulls, and it's still on the eth setting, but it snapped right to 8100-8200 when I went WOT. One thing I did find that's interesting is that the squish is pretty tight - .050 or just a touch under. Indy Specialty's instructions say .060 and more is safe, any less could be a problem. I'm pretty sure I've got aftermarket domes, but don't know from whom. I never have gotten a det warning on this sled at any time, FWIW. If the engine is ok despite having a tree branch jammed into the spinning clutch, I might run some avgas. Maybe it's just on the edge of det but not tripping it. About the only negative with the new pistons is I'm pretty sure it vibrates more; not surprising considering the weight for piston and pin is 20oz vs. 17.1 for the Wossners.

Anyway, for now I need some parts (please PM me if you've got the lower plastic fender, a spare shock, sway bar and link), and even though it seemed to run like nothing happened after, I'm definitely checking crank runout and cylinder phasing. Even with that, I almost wonder if at least replacing the PTO bearings would be wise, but I just can't bear to take it apart again this season. If the runout and phasing checks out, I'm just going to run it.

 

[BeartoothBaron]

I just finished checking out the crankshaft, and it looks like my sled took a bullet to the chest without doing any vital damage. The runout checks just the same as when I put the crank in (right at .001), and the phasing appears to be within a degree or so. I can't find anything broken or cracked structurally, motor mounts look fine, yada yada yada. If blowing a belt can throw out a crank, then I'm really lucky jamming a log into the clutch didn't damage it. For sure, the suspension took the brunt of the impact, but it did jam the clutch pretty hard too. Judging by the scuffing on the clutch, it did spin at least a full revolution (probably a few) before it stopped, so apparently it didn't crash to a stop too badly. I'm still concerned about the health of the bearings, but hopefully if it crashed hard enough to damage some bearings, it'd also cause runout issues. Maybe the upgraded bearing setup saved my bacon... I can't be sure I'm out of the woods yet, but it's a small miracle it didn't do some major engine damage on the spot!

 

[KootenayD]

I just finished checking out the crankshaft, and it looks like my sled took a bullet to the chest without doing any vital damage. The runout checks just the same as when I put the crank in (right at .001), and the phasing appears to be within a degree or so. I can't find anything broken or cracked structurally, motor mounts look fine, yada yada yada. If blowing a belt can throw out a crank, then I'm really lucky jamming a log into the clutch didn't damage it. For sure, the suspension took the brunt of the impact, but it did jam the clutch pretty hard too. Judging by the scuffing on the clutch, it did spin at least a full revolution (probably a few) before it stopped, so apparently it didn't crash to a stop too badly. I'm still concerned about the health of the bearings, but hopefully if it crashed hard enough to damage some bearings, it'd also cause runout issues. Maybe the upgraded bearing setup saved my bacon... I can't be sure I'm out of the woods yet, but it's a small miracle it didn't do some major engine damage on the spot!

I was trying to find a minute to reply to your first post but been mad busy...

I was just going to say that if you mangled the crank or did any damage to those PTO bearings or the case, you'd see it on the runout. .001 is a nice digit. Piece her back together and ride the piss out of what's left of winter!

 

[Blancheeron]

I experienced a similar subtle hesitation on a turbo 4 stroke sled with forge pistons. I scoped the motor after the ride and found it seized the ring in the ringland and scarred the entire cylinder. I fixed the hard parts and never had another issue.

 

[Blancheeron]

I experienced a similar subtle hesitation on a turbo 4 stroke sled with forge pistons. I scoped the motor after the ride and found it seized the ring in the ringland and scarred the entire cylinder. I fixed the hard parts and never had another issue.

jiofi.local.html tplinklogin​