why are 4 strokes more reliable

[jayzx10r]

i mean worknig on the banshee is about as mindless as it gets so what makes 4strokes that much better?(mechanicly)

I think the part that makes the Banshee better is "the mindless" part you elude to. No valve spring retainers, cam timing, cam chain tensioner, etc.

 

The greatest positive attribute with the 4-stroke design is it's oil bath that's primary function is parts/component cooling and secondary lubrication due to the pressurized oiling system.

 

In order for a 4-stroke to be competitive with a 2-stroke, it must be in a significantly higher state of tune. If you look at the parts that come out of any of the modern stock 4-stroke ATV/dirt bike 450s, they would have been considered factory race parts 10 years ago. Piston skirts so short that the piston pin boss protrude farther down than the piston skirt, so you set the piston down on a flat surface...it rocks to the side instead of sitting flat. Exotic metals, alloys, forgings are all a part of the technologies the Banshee has not been a part of.

 

Banshee engine technology has not changed in 20 years so use the 20 year mindset. An XT500 put out a whopping 30 HP back in the day...at the crank. That would be 21 HP at 350CCs....something like 15 RWHP. If you consider what it takes to get a 4-stroke to match what your 20 year old engine puts out with just an exhaust/jetting change, then one can appreciate the efficient design of a 2-stroke.

 

Imagine how a Banshee would run if they simply redesigned a 2-stroke motor that incorporated 2-YZ250 cylinders to a modern revised engine case with a slick shifting transmission and new design clutch mated to aYFZ450 chassis....NOTHING could touch it!!

 

As an addition pertaining to the longevity/reliability of the 4-stroke design, my buddies Yamaha YZF426 had a recommended crank replacement interval of 40 hours!! That is a long time!!

 

I think that what makes the 4-strokes so attractive to people is that they are easier to ride. Anyone can hop on a 4-fiddy and roost...no skills required. You can leave those green/yellow powerbands off of your bike and ride like a hero!!

 

To summarize, "Better Is In The Eye Of The Beholder".... Personally, I don't think they are better...but others may disagree.

[RZBansheeMan]

I would convert to fuel injection in a heartbeat. I know of at least two other members on this forum that are well versed in EFI applications. But what makes you think Fuel injection would revive two strokes? Besides making tuning a whole lot easier. From what I have seen on current production fuel injected ATV's most companies have opted to use a speed density FI setup which is not ideal for making two strokes more EPA compliant. But what do you want to have a mass air meter and o2 feedback on an ATV. I just don't think it would be practical for the kind of enviroment ATV's are subjected to. I don't think Fuel injection will net longer life to an properly tuned engine. Perhaps it would defer some laziness of ATV riders being able to compensate for altitude changes without re jetting ect.

 

Speed Density from a performacne point of view would be preferable due to it's limited sensor feedback, just not form a EPA compliance view. Which is the real reason why two strokes are on their way out.

 

Well it is my opinion that 2 strokes could meet if not exceed the EPA requirements with the addition of F.I. When I attempt my F.I. Banshee project, I am going to go the Microsquirt route and follow how GM went - using both a M.A.F. and M.A.P. sensors just to see if it can be done.

 

I guess I don't really care if the 2 stroke is never brought back, I will always have mine. :biggrin:

 

I also would have to disagree on the fact that you suggeested a F.I. engine doesn't last any longer than a properly tuned carbed engine. Just because it is F.I. doesn't mean that maintenece intervals decrease as some people treat them, but when a finely atomized fuel is sprayed directly at the intake opening rather than fuel being drafted from an orffice like a carb, engines run smoother and more efficient netting longer life than engines that don't run quite as smoothe.

 

I do agree however that it is probably not real practical on atv's as a carb just because of the environments and such they are put thru.

[FireHead]

You are off your meds again, aren't you?

 

LOL....

 

:yelrotflmao: :yelrotflmao:

...........either that or he has been locked in his bed room building model airplanes again. :biggrin:

[kojack]

I cant say their more reliable. My bud works at the suzuki kawi shop and he says their not more reliable and more expensive to fix. I havent had to wrench my engine for 2 years.

[Michael Jackson]

they arnt, its just a myth, 2 strokes are cheaper and easier to work on, and if put together, tuned right, will last just as long if not longer than the new high strung thumpers, namingly the 450's, at least the raptor has a more conservative compression ratio, but from what ive seen they are definatly not as reliable as an old 2 stroke, too much technology = more things to go wrong = gettin towed outa the woods by 2 stroke

[strokerace]

THE ONLY REASON IS BECAUSE THEYRE SLOWER PLAIN AND SIMPLE

[ojcool]

Well it is my opinion that 2 strokes could meet if not exceed the EPA requirements with the addition of F.I. When I attempt my F.I. Banshee project, I am going to go the Microsquirt route and follow how GM went - using both a M.A.F. and M.A.P. sensors just to see if it can be done.

 

I guess I don't really care if the 2 stroke is never brought back, I will always have mine. :biggrin:

 

I also would have to disagree on the fact that you suggeested a F.I. engine doesn't last any longer than a properly tuned carbed engine. Just because it is F.I. doesn't mean that maintenece intervals decrease as some people treat them, but when a finely atomized fuel is sprayed directly at the intake opening rather than fuel being drafted from an orffice like a carb, engines run smoother and more efficient netting longer life than engines that don't run quite as smoothe.

 

I do agree however that it is probably not real practical on atv's as a carb just because of the environments and such they are put thru.

Well, hopefully we will both be wrong and they will redisign the banshee with current technology... And powervalves!!!!!! I would like to see EFI on everything just cause it's a heck of alot more convinent to tune as long as you have enough injector duty cycle to get the fuel you need. And a way to properly command that fuel of course.

[RZBansheeMan]

Well, the injector duty cycle and F.I. controllers are out there.

 

http://www.smcomp.com/~smurph/RZ-EFI/index.html

 

http://www.rzrd500.com/phpBB2/viewtopic.ph...asc&start=0