Why are 2 stroke 800cc motors so unreliable?
- Thread starter TIM
- Start date
I have almost 4000 miles on my m8 turbo not one failure. I cant believe this 800 cat hasn't blown to pieces! Some motors are better than others plain and simple! I would love to have a pro with a cat 800 in it but I will not put my vacation on the line with that Polaris junk motor.
me too
S
snowmobiler
Well-known member
i want a smooth running etec in a skidoo xm chassis.
Ah no as a matter of fact the Yamaha engine will be in arctic cat sleds in 2014.I got the facts from a Yamaha rep.
Back in the day a good running 670HO was putting out close to 140HP, my 98 670 Summit that I gave to my son is still running after 16 seasons (crankcase has never been apart) 2 years ago we put in new pistons just for something to do---the wear in the cylinders was so slight you could not measure it---after 14 years we put stock size dual ring pistons back in it and now it worries my 800HO to death, side by side to 90mph. When did it become exceptable for a snowmobile engine to only last one season? This 670 has never seen synthetic oil and we clean the rave valves maybe every 5 years cause we think we should not because they need it. If they could build them like that 20 years ago they can do it now but like everything else snowmobiles have become a "disposable product", use them 1 or 2 years and sell them or in most cases part them out after the motor blows. I am really surprized Yamaha has not cashed in on all the motor problems the other makes have had but they were too stupid to admit their own weight problem I guess.
F
freekweet mods
Well-known member
Through the eighties and nineties, in most cases the engine would last until the chassis was completely trashed.Many Mach Z's,Storm's,Thundercats,and V-max 4's would go over 4000 miles before needing a top end and then go another however many thousand before needing a crank. If you look at the old 500cc single cylinder dirt bike engines that seemed to run forever without crank problems, I would dare say a 800cc twin could be built to last longer if the manufacturer wanted to.
2006 M7. Bought it brand new 0 miles out here in California. Just sold it last summer to buy a proclimb. The m7 I sold with 8100 MILES. NO JOKE! Replaced the pistons at 4500 miles and they looked great. (REDLINEBILL on here did the top end). Bottom end is all original. Stock motor including a stock can. Put spark plugs in , cleaned the power valves and changed DD oil regularly. Lost a primary spider at 5k miles. Thats it. 1000 miles on my Proclimb with 0 issues.
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snowmobiler
Well-known member
watcha talkin bout willis?
sorry
sorry
my 2009 m1000 currently has 9907miles stock motor and i just ended my season. i feel like you guys out west run the motors wide open throttle a hell of a lot more than i do in the east. I ride trails and offtrail 50/50, but the offtrail is no where near what you guys ride.
I know when im off trail im high up in RPMs the whole time.
i found out from being on here that you guys consider high mileage 3000miles where i consider high mileage around 5000
I know when im off trail im high up in RPMs the whole time.
i found out from being on here that you guys consider high mileage 3000miles where i consider high mileage around 5000
High mileage is different for every brand. 5000-6000 miles on a Cat motor out west is common. Not so with a Dragon, Pro or XP.
I'm not going to hate on any other manufacturers, brands, models, ect. This is my experience, on my sled and no BS. And yes the terrain we ride out here in Cali is all backcountry with very little groomed trails. The snow is very heavy and the hills steep. The M7 was flogged its whole life, I beat the hell out of that sled......couldn't kill it. My friend has it now and it has been running great all season.
My experience with that snowmobile is what led me to call Michelle at OTS and order a new ProClimb, if I left AC and had any motor or drivetrain issues I would have kicked my own *** for leaving a manufacturer that was sooooo reliable for me, and so far so good, that 800HO suzuki twin pulls strong!!!
My experience with that snowmobile is what led me to call Michelle at OTS and order a new ProClimb, if I left AC and had any motor or drivetrain issues I would have kicked my own *** for leaving a manufacturer that was sooooo reliable for me, and so far so good, that 800HO suzuki twin pulls strong!!!
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Longevity
Willis: "Stock motor including a stock can. Put spark plugs in , cleaned the power valves"
Two very important ingredients for long life: 1) Balanced crank and 2) Reliance on the MFR engineering crew to make good choices.
Please note these Suzuki 800 and 700 cc motors have a 70 mm stroke. Is this a co-incidence that reliability and slightly shorter stroke go together?
Willis: "Stock motor including a stock can. Put spark plugs in , cleaned the power valves"
Two very important ingredients for long life: 1) Balanced crank and 2) Reliance on the MFR engineering crew to make good choices.
Please note these Suzuki 800 and 700 cc motors have a 70 mm stroke. Is this a co-incidence that reliability and slightly shorter stroke go together?
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I forget where, but I remember reading a while back that a twin engine size of 800 is just too big to have the same reliability as a triple or a smaller twin. It has to do with the difficulty of cooling those big pistons down, with the breathing characteristics of a huge twin making things worse. There's also a ton of weight swinging around in the bottom end , which makes crank reliability problematic. These are reasons why Yamaha never built a twin larger than a 600.
The other issue at work is emissions regulations. Somebody from Polaris stated in a magazine interview last year (again, I forget which magazine) that it costs ten times the amount to design an engine as it did in the late 90's. This is because they have to go through a huge hassle and expense to get the EPA certification. The engine has to be designed around it. Then, whenever they want to make even a relatively minor change to it, they have to go through the whole process again.
There have been threads on here about why the 800 CFI has been so troublesome, and Polaris can't "get it right". Apparently Polaris, unlike other manufacturers, didn't use their emissions exemption on the 800 CFI engine, and this forced them to immediately meet the new regulations on the 800 dragon. Running extremely lean in the midrange was the only way they could meet the regs, and was a major reason that that engine was a blowup special. If I'm not mistaken, the loose pistons had something to do with meeting emissions as well. It's also the reason they are so stingy with oil injector settings on the pro.
Like Jaynelson said, these motors are putting out a lot of hp per cc. An Indy 500 or XLT wasn't a high performance engine. These are. We're getting close to the MX bike level of power per cc. As such, top end replacement intervals are coming down as performance goes up. On a 250 two stroke MX bike, anything more than about 20 hrs. is running on borrowed time for a piston. Suzuki used to spec a new piston on the RM125 every two hours. Yamaha used to include a top end kit with a new YZ just so the first one was free. Nobody blew up a 250 after 40 hours on a piston and blamed the bike or the manufacturer. If you were considering buying a year old bike and the guy hadn't done a top end yet, you knew that was the first order of business after you brought it home. We're getting to the same level of performance, and parts replacement intervals, with sleds. It might be worth asking "Do I really want a high performance engine?" If you do, it might be wise to forget about the warranty and get used to working on the thing yourself, doing top ends every 40 hrs. or so, and bottom ends every 100. If not, maybe the current crop of 800s is not the best choice.
The other issue at work is emissions regulations. Somebody from Polaris stated in a magazine interview last year (again, I forget which magazine) that it costs ten times the amount to design an engine as it did in the late 90's. This is because they have to go through a huge hassle and expense to get the EPA certification. The engine has to be designed around it. Then, whenever they want to make even a relatively minor change to it, they have to go through the whole process again.
There have been threads on here about why the 800 CFI has been so troublesome, and Polaris can't "get it right". Apparently Polaris, unlike other manufacturers, didn't use their emissions exemption on the 800 CFI engine, and this forced them to immediately meet the new regulations on the 800 dragon. Running extremely lean in the midrange was the only way they could meet the regs, and was a major reason that that engine was a blowup special. If I'm not mistaken, the loose pistons had something to do with meeting emissions as well. It's also the reason they are so stingy with oil injector settings on the pro.
Like Jaynelson said, these motors are putting out a lot of hp per cc. An Indy 500 or XLT wasn't a high performance engine. These are. We're getting close to the MX bike level of power per cc. As such, top end replacement intervals are coming down as performance goes up. On a 250 two stroke MX bike, anything more than about 20 hrs. is running on borrowed time for a piston. Suzuki used to spec a new piston on the RM125 every two hours. Yamaha used to include a top end kit with a new YZ just so the first one was free. Nobody blew up a 250 after 40 hours on a piston and blamed the bike or the manufacturer. If you were considering buying a year old bike and the guy hadn't done a top end yet, you knew that was the first order of business after you brought it home. We're getting to the same level of performance, and parts replacement intervals, with sleds. It might be worth asking "Do I really want a high performance engine?" If you do, it might be wise to forget about the warranty and get used to working on the thing yourself, doing top ends every 40 hrs. or so, and bottom ends every 100. If not, maybe the current crop of 800s is not the best choice.
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Most 600s run a shorter stroke....but take my iqr 600....same stroke as the 800.....8600 plus rpm......three hard seasons of riding without anything except oil and gas....130/.6 = 216.6 hp/l
could some of these "super oils" be causing some of engines failing like not enough protection from corrosion when the sled is not running?? Back 10 years ago there was not much of a choice for oil. Now every time I turn around their is some new witches brew marketed for keeping your valves clean.
I also agree with we are riding race motors on a witches brew of fuel. Back in the early 2000s to get the power the stock 800 twin cylinder engines are making today, you would have the thing running on race gas, with every engine mod known to man.
I also agree with we are riding race motors on a witches brew of fuel. Back in the early 2000s to get the power the stock 800 twin cylinder engines are making today, you would have the thing running on race gas, with every engine mod known to man.
