2 stroke technology as compared to 4 stroke

[RamsesRibb]

A good Kevin C. article .

http://www.cycleworld.com/2015/08/20...-kevin-cameron

That guys sounds like a wimp. That 200hp 500 seems like the perfect engine for my Trisport.

[RamsesRibb]

I think this is what someone was referring to about Honda's plans.

http://newatlas.com/honda-two-stroke...8529/?amp=true

[RIDE-RED 250r]

Rotax has been leading the way on 2-stroke advancement and compliance with the more stringent EPA standards with their ETEC 600 and now 850 2-stroke sled engines. Technology they inherited when they bought out OMC who was the umbrella under which Johnson and Evinrude outboards were manufactured. The outboard DI system was a bit different from what I have read, but it wasn't too difficult for Rotax to adapt that system and implement it on their sled mills. ETEC came out in '07 if I recall... at the time of introduction the 600 was claimed to be capable of close to 20mpg and the 800 16mpg under normal riding conditions. Obviously that number can change with riding habits and conditions... I haven't been into sleds and following things in that area for a few years now, they may have improved since then.

The tech is there, the industry is against it, not sure why. Some have hypothesized that the big manufacturers (Honda being the primary offender) are so invested in 4-stroke that they used their influence on the racing circuit to put the final nail in the coffin of the 2-stroke mill. They simply do not want to market 2-stroke engines any more... As I said, I have seen it hypothesized in that way, not sure if I go along or not..don't really care though as my wing-dingers are still in my garage with no plans of replacing with anything "new".

I don't race, but I have ridden all of the major 450's except the Kawi. 86t3 is right, torque all over the place and I can see why they are the choice of so many racers. It makes sense to me.

[cr480r]

All the efficiency and rideability in the world will never make me enjoy 4-stroke sounds... I ride purely for enjoyment. I find the typical 2 -stroke power build very exciting .. I really enjoy the sounds and smells... And I enjoy working on them. They are powerful light, simple, affordable, and reliable... That's all I need

[atc300r]

Honda built a two stroke years ago to meet smog requirments I think it was $650,000 Cr 250 prototype.

[Herboso]

How much do you think California's strict OHV registration program influenced the issue?

[RubberSalt]

Look at modern snowmobile engines. 2 strokes have come a long way, long gone are the days of the piston ported slobbery gas spitting engines.
They're really not any harder on gas than a 4 stroke, and the emissions aren't much worse. Fuel injection directly into the transfer ports, electronic power valves, and electronic oil pumps. Only hard parts seems to be keeping any 800 from grenading evey 5000 miles.

Sent from my SM-G903W using Tapatalk

Gearheadtom is right. The sled community has been pushing the envelope of the 2 strokes. Not only with emissions, but all sorts of new technology to help with emissions. The 800s crapping out after 5k is pretty good if you ask me. They are pushed hard, just like the 450s. Expect service life to crap out fast!

Heres an example of the power produced my modern 2 strokes. These are set up to operate in a narrower powerband to take effect of the CVT, but none the less.
2016: Rotax 800r e-tec - 165HP. Thats 82.5HP per 400cc cylinder
2016 Artic Cat XF 6000 - 600cc, 125hp, 62.5hp per 300cc. This is a tame engine. Made to last.
2016 Ski-Doo x with T3 package, 147+hp. 73.5hp per 400cc.
2017 Ski-doo 850 e-tec, 170HP, 85 per 425cc.

These are lean settings used to meet the EPA requirements. Many aftermarket set ups push the 800ccs well into the 180-190hp range. Little.. ridiculous!

These are all fuel injected. They have oil systems that use next to no oil. No more mixing, and i don't mean oil is injected into the gasoline. The oil, is closer to the method used on a automobile. It's pressurized and sprayed directly onto bearings and the places that need it. most cars leak more oil than these use in a season!
Modern sleds have adjustable compression. Yes, compression. As you drive higher in altitude, your compression drops due to lack of air density. To compensate for this, manufactures have begun including adjustable domes. With the turn of a wrench, compression can be increased. Offset jugs are showing up more often these days. Shifting the center line of the jug towards the exhaust a few mm makes a big difference in how much power is transmitted to the piston, opposed to the friction and the cylinder wall.

Any 2 stroke can be tamed the same way a 4 is, heavy flywheels. They help distribute the torque more evenly throughout the revolution of the crank. They rev up slower, but maintain the inertia generated by the piston during the combustion process. A pipe designed for a wider powerband also helps. It drops the amount of power, but broadens the torque. The majority of usable power(with gasoline!!) extracted in both 2 and 4 strokes is in the first 10-20 degrees atdc. The combustion process is complete by 25 degrees atdc. After that, it's mostly rotational momentum carrying the engine to the next power stroke.

[christph]

How much do you think California's strict OHV registration program influenced the issue?

Yes, unfortunately California's regulations significantly influence manufacturers because they are the biggest market in the country.

[oldskool83]

Ride both and see which one does everything and then some. Then come back and see if you feel the same about your argument. today 4 strokes are nothing like lets say 30 year old 4 strokes...they remind me of one thing, a sport bike 4 stroke and to that i am fine with everything they do.

I have one 2 stroke left....why, not sure I guess I thought it would be cool to have something old yet.

[Hurley250R]

Blow one up and see how much you love it then. Two strokes about $300 repair while a 4 stroke is $1200+

[oldskool83]

I have no issue with spending the money to build one. blow up a 2 stroke bottom end and top end and you are well over $300. Replate alone is $140 at most placed, plus all your bearings this and that. It's not that simple. I've rebuild 2's and 4's and not had that issues of spending money on a 100% fresh motor, not a new piston and call it a day. In today's day and age good maintenance and not revving the piss out of stuff really goes a lone way.

Maybe i have not learned anything in 27 years of riding about everything.

[RIDE-RED 250r]

It's a fact that the "modern" 4-strokes, mainly the performance oriented 450s are very high strung mills and will not enjoy the service life of your older school thumpers. With anything you build or design, when you push for higher and higher power and RPM potential in a given displacement, you WILL suffer loss of service life and accelerated wear of the major engine internals. This is true of anything from chainsaws to wheelers, to boats, to supercharged BBC's set up for drag racing and making 800hp.

Now I would tend to agree with you oldskool83 that most 450 major components are priced about the same as the old 2-strokes... But where costs with overhauling a 450 can and do climb well past the cost of overhauling a wing-dinger is when you start talking cams and heads. And they do go bad and/or get damaged to the point they need replacement when someone pops one at times. And I agree, good maintenance and not abusing the engine will get you farther down the trail/track.

I remain impressed with how they have designed these modern thumpers to run. I have owned a couple of Z400s in recent years. Liked how they ran, had some trouble with one I couldn't figure out... Did a fresh piston and crank with crank bearings thinking it would cure it and it didn't. Sent them both packing in favor of a 350x and 400ex. Nice quads, run strong, but HATE dual cams and messing with shims to adjust valve lash!

[RubberSalt]

Oldskool is right not overrevving and maintenance will keep both engines going for a long time. Below is some ball part ideas of what it takes in the case of catastrophe and the difference when maintaining the engine. I've decided to compare a trx250r and the yfz450r. The labor cost are from local sources in wichita ks. The key is proper maintenance and not running the engines into the ground... Expect the below the general maintenance about ~100 hours on both machines. You can expect to wear a crank out on a 2 stroke a lot sooner than a 4 stroke. Higher oil ratios augment this greatly, but it's inevitable. Its the trade for the extra HP.

2 stroke typical 250R
Worn top end on iron sleeve=$130 for piston. $40 for a bore.

Worn top end on plated top end, $130 for piston and $140 for replate
Trash a crank.. $75 bearings seals and gaskets, $120 for rod, $90 for labor

Worst case, trashing the bore and crank: $565

General maintenance:
Piston:$130
Gaskets:$25
$155 total


4 stroke -based of the yzf450r
Worn top end on iron sleeve=$150 piston and $40 bore.
Worn top end on coated top end, $150 for piston and $140 for replate

A bad 4 stroke day
Float a valve - $90 per valve<- they are using titanium in the high performance machines these days.
Piston $150
valve guide $150 for Labor+parts
seat $40 for repair +parts
Gaskets $40
$470


Oil pump locks up or oil starvation due to plugged filter
Piston $150
Replate $140
Cam $200
Rod $150+$90 labor
valves(probably fine)
Gaskets $40
$770


Top end wear and tear due to lack of maintenance: 5 valves. $450 + 5 seats @ $40 each
Piston: $150
Timing chain being stretched $20
Worn chain guides: $60
Gaskets $40
$930

Top end general maintenance - assuming all other is maintained properly.
Timing chain: $20
Piston: $150
Gaskets: $40
$210


Grenade a cast piston from over revving for to long. Oh god lets not go there.


Didn't even want to get into covering the transmission causing potential problems on the 450s. or a timing chain that jumps and smashes valves

[RubberSalt]

http://www.3wheelerworld.com/showthr...r-rebuild-cost throwing this out there.

[86T3]

Maintenence is more expensive on the new 450s, that is true for sure. I got a ridiculous deal on a full mx ready 08 yfz this year with a motor in a box. I bought it because I have a rebuilt yfz motor that has been stolen from me along with the rest of the quad, and I hoped that I would be getting it back this summer. I haven't gotten it back yet, it's a whole other story, so I took the mx motor in to my shop to get it checked out. It came with a new piston and top end gasket kit, I was hoping it could just be put back together and I'd be good to go. Well, it was a race motor and even though it didn't blow up it needs practically everything. The timing gear on the crank was getting wore into or something so it needs a new crank. Needs a ton of bearings, all the valves are out of spec, it came out to around $1500 in parts and like 250 for labor. I picked it up and payed for disassembly, I couldn't swallow that bill. And thats not including the price for a new piston because I had one! They said a yfz came in last month that needed a a rebuild and a new head, that guy ended up doing the same thing I did. I still think the 450s last longer than 2 strokes though, there are examples of each motor that have been together for many years with good maintenence and still run good. But I would like to know where you guys are getting cylinders replated for 140, that's a really good deal