Why are 2 stroke 800cc motors so unreliable?
- Thread starter TIM
- Start date
May be some truth to this.
Lets face it, the Poo 800 has been the worst engine out there for what? 6 years running (not counting the Edge VES engines).
Poo gets a great chassis finally and they are selling like hotcakes. 3 years of bad motors in the Pros and everyone know about it thanks to the innerweb and they are still flyin out of the dealerships like they're on fire.
He!! even I, who typically will not buy something that is a known problem machine (be it sled, truck, weed whipper, toaster, etc) went and bought a '12 Pro. Granted I got a deal on it that was cheap enough that I could drop a new engine in it on my own dime and still be out less than a new sled, but Poo isn't completely crazy, just crazy like a fox!
Would be interesting to see their warranty expenses vs. their profit from non warranty repairs/replacements.
S
snengineer
Well-known member
My first thought when I read the title, why inst this thread in the Polaris section. Then I opened the thread and read it and thought, why isn't this thread in the Polaris section?
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snowmobiler
Well-known member
maybe the poo section is maxed out on broken threads?LOL
Just as many have already stated, these engines are high performance engines right out of the box. Essentially race engines. How long do you expect them to last? Sure they could make them more reliable, but it would cost a lot more and the manufacture isn't going to pay for that you are. Are you willing to pony another couple grand on a new sled so you get a few thousand more miles out of it. The bean counters have it figured out to the point where they know they will have some warranty claims, but the majority of engines will make it off warranty. After they what do they care what happens to it? This doesn't just apply to snowmobile engines, it applies to just about everything.
Also it seams that most of you guys never raced motocross back in the 2 stroke days. Top end every 10 hours, no one really complained about it either.
Also it seams that most of you guys never raced motocross back in the 2 stroke days. Top end every 10 hours, no one really complained about it either.
so if its mostly about the hp/cc of the engine, and i understand and agree these are pretty high strung small engines pulling severe duty, but once again why is it that the lowest powered engine in the class has the highest failure rate and engines like the m7 and D7 put out ruffly the same horsepower but in a smaller displacement which would intern raise the hp/cc ratio even higher seem to last alot longer? i dunno about the poo 700, but as far as the shorter strokes and all that stuff people are saying as why the 7s last long if i'm not mistaken the m7 is the same stroke as the m8 so that should take that theory out of the water shouldnt it?
my m7 has just under 4200 miles on all original internals and the majority of them miles are with the flipper held to the bars in off trail mountain riding and still runs like a raped ape. it has also had a modified head and SW single pipe on it for the majority of its life which "should" in turn create more ponies which would just increase the hp/cc ratio right?
so from my understanding the pro is ~800cc's putting down 135-145ish hp depending who you ask, and my m7 is ~700cc's putting down roughly the same hp then my hp/cc ratio would in turn be higher than the poo. soooo from my calculations, if you take the poo failure rate......carry the 1........ dot the T........ roll this # over..........add this #.......and round here, my sled should have blown up roughly 8 1/2-9 times by now.
guess what i'm sayin is i lean more towards its a manufacturer issue than simply hp and displacement issue with why some last and some dont.
P.S.-hopefully cat wont screw up the best thing goin for them when they start producing there own engines.
P.P.S.-i'm bored
my m7 has just under 4200 miles on all original internals and the majority of them miles are with the flipper held to the bars in off trail mountain riding and still runs like a raped ape. it has also had a modified head and SW single pipe on it for the majority of its life which "should" in turn create more ponies which would just increase the hp/cc ratio right?
so from my understanding the pro is ~800cc's putting down 135-145ish hp depending who you ask, and my m7 is ~700cc's putting down roughly the same hp then my hp/cc ratio would in turn be higher than the poo. soooo from my calculations, if you take the poo failure rate......carry the 1........ dot the T........ roll this # over..........add this #.......and round here, my sled should have blown up roughly 8 1/2-9 times by now.
guess what i'm sayin is i lean more towards its a manufacturer issue than simply hp and displacement issue with why some last and some dont.
P.S.-hopefully cat wont screw up the best thing goin for them when they start producing there own engines.
P.P.S.-i'm bored
J
Jaynelson
Well-known member
^ I think I already answered that about 5 times, but I'll try again....
It's not that engines can't live at this specific out put. They can....they do. They can live at significantly higher specific output levels, as evidenced by the many boosted 800's running around, some of which with lots of miles and minimal issues.
All I'm saying is that the higher the specific output, the more it exacerbates any small flaw (design or manufacturing), inconsistency, tolerance issue/tolerance stacking, lack of maintenance, improper fuel or lubrication, etc, etc, etc, etc.....so when the manufacturer's have a small "miss," it can easily lead to catastrophic engine failures. Even your M7....they were a reliable engine in general, but it's not like no one ever blew one up. It's not like the dealer never saw the odd one in for a motor job. My truck has a Toyota 4.7L V8 that is used in 5 different Toyota/Lexus models across 9 model years....I worked with Toyota for about those same 9 model years, and you know how many 4.7L engines we replaced or rebuilt? 0....as in 0 ever. Why can that happen and it has never happened with any sled motor? 2 things.....one is money, and the other is the nature of the beast. Why are some better than others? That's a technical question and you would really have to get into the math and materials of each to compare. Indy Dan had some great techincal discussion on the Pol 800 in the Pol section if anyone cares to look it up....
It's not that engines can't live at this specific out put. They can....they do. They can live at significantly higher specific output levels, as evidenced by the many boosted 800's running around, some of which with lots of miles and minimal issues.
All I'm saying is that the higher the specific output, the more it exacerbates any small flaw (design or manufacturing), inconsistency, tolerance issue/tolerance stacking, lack of maintenance, improper fuel or lubrication, etc, etc, etc, etc.....so when the manufacturer's have a small "miss," it can easily lead to catastrophic engine failures. Even your M7....they were a reliable engine in general, but it's not like no one ever blew one up. It's not like the dealer never saw the odd one in for a motor job. My truck has a Toyota 4.7L V8 that is used in 5 different Toyota/Lexus models across 9 model years....I worked with Toyota for about those same 9 model years, and you know how many 4.7L engines we replaced or rebuilt? 0....as in 0 ever. Why can that happen and it has never happened with any sled motor? 2 things.....one is money, and the other is the nature of the beast. Why are some better than others? That's a technical question and you would really have to get into the math and materials of each to compare. Indy Dan had some great techincal discussion on the Pol 800 in the Pol section if anyone cares to look it up....
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rmscustom
Well-known member
so if its mostly about the hp/cc of the engine, and i understand and agree these are pretty high strung small engines pulling severe duty, but once again why is it that the lowest powered engine in the class has the highest failure rate and engines like the m7 and D7 put out ruffly the same horsepower but in a smaller displacement which would intern raise the hp/cc ratio even higher seem to last alot longer? i dunno about the poo 700, but as far as the shorter strokes and all that stuff people are saying as why the 7s last long if i'm not mistaken the m7 is the same stroke as the m8 so that should take that theory out of the water shouldnt it?
my m7 has just under 4200 miles on all original internals and the majority of them miles are with the flipper held to the bars in off trail mountain riding and still runs like a raped ape. it has also had a modified head and SW single pipe on it for the majority of its life which "should" in turn create more ponies which would just increase the hp/cc ratio right?
so from my understanding the pro is ~800cc's putting down 135-145ish hp depending who you ask, and my m7 is ~700cc's putting down roughly the same hp then my hp/cc ratio would in turn be higher than the poo. soooo from my calculations, if you take the poo failure rate......carry the 1........ dot the T........ roll this # over..........add this #.......and round here, my sled should have blown up roughly 8 1/2-9 times by now.
guess what i'm sayin is i lean more towards its a manufacturer issue than simply hp and displacement issue with why some last and some dont.
P.S.-hopefully cat wont screw up the best thing goin for them when they start producing there own engines.
P.P.S.-i'm bored
There is no way a m7 and the polaris 800 are putting out the same power.
I own both and in no way will my mildly modded 700 even compete with the stock cfi 800. I feel all the 800s are really close and the hp ratings are a joke and whatever the poo gives up on the top end it makes up for it in throttle response and low and mid range power (how you ride depends if you agree with that or not).
My 7 has over 6000 miles and has been flawless. I freshened up the top end at 4000 miles and once I got in there I realized it was just for fun... But with that being said I have no problems with putting new pistons and rings in my polaris every year for how good that sled works as an entire package.
C
cbc24
Well-known member
Either way I think all if your bantering is a bunch of bs lol. **** happens, it is what it is. 4stroke or not I know enough people whom have blown every brand and everything up. I've owned a cat, poos and a doo and its all the same crap 600 or not. Its inevitable if your going to be purchasing a sled to ride the crap out of it will blow up, that is a fact, its just a matter of when some cases sooner than others.
S
snowmobiler
Well-known member
a twin pipped m7 will hang with new 800's for 10k less and last 10 years longer.
At least they try to offer some kind of warranty. Pretty good for a racing engine if you ask me. The extra maintenance involved, is just par for the course when it comes to 2 stroke engines IMHO, And just has to be accepted if you ride these things.
Reason?
If you can not understand and it and makes no sense from any other prospective: The reason has to be MONEY. The crank is the single most costly assembly on the whole machine. Balanced cranks cost even more.
Then the ugly truth: The snowmobile industry currently does not have a big enough economy of scale to justify engine improvements beyond lawful emissions requirements the last 10 years. 3D Rave valves, CFI, Etec, case/ transfer / reed injection and the like have cleaned up the motors and improved fuel economy. However when you think about it; 800's 10 years ago still made 140 to 155 HP no problem.
If Rotax could afford to make their own 800 pistons instead of sourcing mostly good (but occasionally screwed up - 2001 and 2011 come to mind) product from Elka and other sub suppliers: They would, however the economy of scale is not there.
If you doubled the price of the engine to mandate reliabilty: snowmobile sales would go from 140,000 a year to 90,000. Yamaha and Cat would leave. Polaris and Ski Doo would charge 27k for a machine and it still would not be any different.
I think the engineers that design these things do the best they can with very limited resources and roll the dice. IMHO Where they make a bad call is on cranks. Balance the thing and charge me an extra $400. The engine will now last the 300 hours the engineer says it is supposed to. Balancing the primary for another 50 might not hurt either!
Jaynelson and 41racing make very good and valid points about parts replacement. I think replacement of the pistons on these motors at 100 to 150 hours (or the moment they have detectable slap) is reasonable. Being watchful and diligent about clutch rebuilds will also help. Finally, clutching the machine properly to avoid heat will also pay dividends in reliability.
Then we get to fuel, oil, warm up, fluid levels, proper service and personal habits that affect reliablity the MFR has no control of. Makes you wonder if these things really are better that we think!
Do not even ask about aftermarket performance parts - that is a very different discussion with even more unique issues!
If you can not understand and it and makes no sense from any other prospective: The reason has to be MONEY. The crank is the single most costly assembly on the whole machine. Balanced cranks cost even more.
Then the ugly truth: The snowmobile industry currently does not have a big enough economy of scale to justify engine improvements beyond lawful emissions requirements the last 10 years. 3D Rave valves, CFI, Etec, case/ transfer / reed injection and the like have cleaned up the motors and improved fuel economy. However when you think about it; 800's 10 years ago still made 140 to 155 HP no problem.
If Rotax could afford to make their own 800 pistons instead of sourcing mostly good (but occasionally screwed up - 2001 and 2011 come to mind) product from Elka and other sub suppliers: They would, however the economy of scale is not there.
If you doubled the price of the engine to mandate reliabilty: snowmobile sales would go from 140,000 a year to 90,000. Yamaha and Cat would leave. Polaris and Ski Doo would charge 27k for a machine and it still would not be any different.
I think the engineers that design these things do the best they can with very limited resources and roll the dice. IMHO Where they make a bad call is on cranks. Balance the thing and charge me an extra $400. The engine will now last the 300 hours the engineer says it is supposed to. Balancing the primary for another 50 might not hurt either!
Jaynelson and 41racing make very good and valid points about parts replacement. I think replacement of the pistons on these motors at 100 to 150 hours (or the moment they have detectable slap) is reasonable. Being watchful and diligent about clutch rebuilds will also help. Finally, clutching the machine properly to avoid heat will also pay dividends in reliability.
Then we get to fuel, oil, warm up, fluid levels, proper service and personal habits that affect reliablity the MFR has no control of. Makes you wonder if these things really are better that we think!
Do not even ask about aftermarket performance parts - that is a very different discussion with even more unique issues!
its because cat blew their wad on motor design and durability. skipped the CLUTCHES, steering components, DD bearing, clutch longevity, fit/finish, cutches (did I say that already?) This is coming from a someone that has 8 various years, models in the shed. Still take the reliable motor over everything.
How about the oil being used? I'm talking synthetic vs dino. Back in the late 90's and early 2000's, running dino oil was the norm. Now it seems that most everyone is running semi-synthetic or full synthetic.
I've heard that full synthetic does not do the crank well for storage because it tends to lose the film, kinda like water on a waxed surface will pool up, only it takes longer for the oil to exhibit that characteristic.
I also spoke with the Valvoline Tech Hotline approx 2 years ago and they told me the reason they don't offer a synthetic 2-stroke for snowmobiles is because it wasn't needed, saying the 2-stroke oil is burned up so fast it wouldn't serve any purpose to use a synthetic, something like that.
I've heard that full synthetic does not do the crank well for storage because it tends to lose the film, kinda like water on a waxed surface will pool up, only it takes longer for the oil to exhibit that characteristic.
I also spoke with the Valvoline Tech Hotline approx 2 years ago and they told me the reason they don't offer a synthetic 2-stroke for snowmobiles is because it wasn't needed, saying the 2-stroke oil is burned up so fast it wouldn't serve any purpose to use a synthetic, something like that.
i wasn't tryin to argue any points with my post, and agree with most of what has been said. more or less was just thinking out loud. i agree there are lots of factors to concider with all this and that all brands can and do have there bad eggs, just some more than others.
i have also heard from a few folks that dino oil does actually do a better job at coating and protecting vital parts, but tend to create more ash and carbon which tends to gum up the exhaust valves on the modern 2 smokes so that's why the synthetic is recommended. in the auto world it is usually recommended to break-in engines on dino oil so it must do something better than the synthetics besides cost less money.
i have also heard from a few folks that dino oil does actually do a better job at coating and protecting vital parts, but tend to create more ash and carbon which tends to gum up the exhaust valves on the modern 2 smokes so that's why the synthetic is recommended. in the auto world it is usually recommended to break-in engines on dino oil so it must do something better than the synthetics besides cost less money.
backcountry
you will be in for a rube awaking when your doo motor goes, down. Doo or poo doesn't really matter. Both have motors with 2 short of a lifespan.
I will say thank you to allsport for stepping up to the plate and doing the right thing.
you will be in for a rube awaking when your doo motor goes, down. Doo or poo doesn't really matter. Both have motors with 2 short of a lifespan.
I will say thank you to allsport for stepping up to the plate and doing the right thing.
Ya, he will. I gave him one
True.
That being said, I now have 1500 miles on my motor with a turbo on my 09 XP motor and all is well. Reliability goes hand in hand with proper tuning, care and maintenance.
U
Unklsnomobile
Active member
I'm not disagreeing with your posts, but you compare the 2 stroke to a 4 stroke in a couple posts. A 4 stroke boosted Yamaha motor can put out 250-300hp/litre and go 10000 miles. Is that because of more money or better tolerances? I think the answer to Tim's question is yes, it's a 2 stroke thing. Having said that, a skidoo rep told me the failure rates on the etecs now are below 1%. That's why they can offer a 4 year warranty.
V
volcano buster
Well-known member
I think this is what you meant to say.
