The smaller 2-strokes are fine engines. Mechanically less complicated than a 4-stroke, so if anything does go wrong, chances are they are cheaper to fix. The only issue might be with riding them on public atv trails in your state. There's been a lot of legislation over recent years trying very hard to push 2-strokes off the market and to restrict them completely because of the emissions, so make sure you can even ride a 2-stroke on the public trails in your state (if you intend to do that).

As for the power, a 2-stroke can make more power than an equal sized 4-stroke, but the key to 2-stroke power is in the cylinder and the pipe. 2-strokes come in basically 2 varieties: ported or reed valved. Reed valved 2-strokes generally make more power than ported designs (at the cost of more parts to maintain/replace). The pipe is absolutely key to the power band. Peakiness in any 2-stroke has everything to do with the pipe. If you design the pipe to provide a broader power band, you lose higher peak HP, but gain the advantages of lower end torque and an easier to ride power band. It makes sense that the smaller, kid atv's are going to have a broad power band to avoid the sudden onrush of the engine "coming up on the pipe". That's not to say a 70cc or 90cc 2-stroke can't put out some serious power. Change the pipe and you can get a lot more power out of it, but in a very narrow band, and very peaky.

4-strokes generally produce more torque at lower rpm's and are overall RPM limited compared to 2-strokes in general. Since HP is a calculated figure derived from the relationship of torque and RPM, that RPM limitation is why a 4-stroke is usually less peak HP than a comparable displacement 2-stroke. In the HP equation you are free to trade RPM or torque as long as the equation remains balanced (Torque x RPM / 5252 = HP). We like to use HP ratings for engines because this tells us the engines ability to do work. The more power it has, the more work it can do (i.e. accelerate quicker or have a higher top speed). However, there is more to it than that. The power has to be usable, or at least controllable, so the engine has to make a certain amount of power across a certain RPM range in order to work efficiently with a minimal number and physical size of gears (the levers we use to alter RPM and/or torque output at the drive wheels).

This why although the cummins diesel in my Dodge Ram makes 600lb-ft of torque (nearly twice that of the Hemi), the Hemi is still 20 more HP because it has a much higher RPM range. Many folks think diesels are used for towing because of the torque, but that's not true. Diesels just last longer and get better gas mileage than a comparable gas engine...it's all economic.

2-strokes are low torque, but high RPM, so they can trade some of that engine RPM for more torque at the drive wheels via the transmission (torque being the twisting force that turns the wheels). The same setup is the opposite for a 4-stroke. More torque, less RPM, so some torque is scarificed to get RPM at the drive wheel via the gearing.

Actual torque output is fairly close on both types of engines in their optinal operating RPM range, but since the 2-stroke has a broader RPM advantage, the drive wheel HP is usually a bit higher, but only when the 2-stroke is "on the pipe". Put a straight pipe and box muffler on a 2-stroke and the 4-stroke will eat it for lunch.

The simpler mechanics of the 2-stroke have some trade-offs. Obviously, the mixing oil and gas. Also, the 2-stroke will need to be pulled apart and decarbonized from time to time. Heavy carbon deposits in a 2-stroke lead to higher compression and overheating and also pre-ignition. Carbon deposits can destroy a 2-stroke.

The best way to avoid fast carbon build up in a 2-stroke is to use a good synthetic oil. I know everyone probably has their favorite, but the engine on my powered paraglider (a 202cc 28HP Italian engine) has lived its life on Amsoil Saber 100:1 synthetic. This engine has almost 600 hours on it and the honing marks on the cylinder are still visible. It has only had to be decarbonized once (at around 300 hours and it was still very clean). I mix this oil at 96:1 because that's how it works out for a small bottle of oil in my 6 gallon gas can. I run it in my chainsaw and weedeaters at the exact same mix. They run as good now as the day I bought them (many years ago). No, I'm not an Amsoil dealer, nor affiliated, just a very happy customer.

Keeping the carb tuned on your 2-stroke is vital as well. If you run it too lean you risk seizing it. 2-strokes will seize a little easier/quicker than a 4-stroke. An overheated 4-stroke usually starts knocking long before it will seize. A 2-stroke will just seem like it is running super great and POW, it'll seize, so keep an eye on your mixture settings.

 

Thanks for all the great input folks.....

The fellow said that the only thing wrong with this one is that the chain adjuster is broke.....

How big of a deal/expense is that on these bikes?

I *do* have a trailer....kind of a pain in the butt getting it but I do have it.....would love to be able to just throw it in the back of the Durango......

I did a search and found a couple threads about the Polaris Predator 90o n another forum (paatving.com).......there were a couple of bad cooments about pre 2004 models....

What you folks say about them? Good/bad?? It seems like parts are easy enough to get....and it does have the Polaris name on it...so that should mean something, right??

I also read that it is actually an offbrand bike with Polaris stickers....is that true???? After looking at the chinese atvs and being less than impressed, I dont want to spend twice the money or more and get the same quality level....

 

You need a bit more detail on the 'chain adjuster.' Does he mean the bolt with the jam nuts on it that is used to rotate the axle assembly (for lack of a better explanation) to tighten the chain or is it one of the four anchor bolts (unlikely)? If the former, it might be a simple fix by getting a new bolt and jam nuts or you may even be able to make the adjustment manually, but more crudely as far as tuning the slack goes. If the latter, you'll likely have to remove the axle assembly to extract the bolt.

IMO, neither is a show stopper, but might factor in to any negotiation.

 

Yes, the mini Preds are made by(don't quote me on this!) AEON overseas. They are definately one of the "upper echelon" though, I wouldn't hesitate to pick up a clean or even new unit. The '07 models are 4 strokes, but I don't think they switched manufacturers for them.

If I can get a Banshee into a Jimmy, you can get a mini into a Durango. Since minis are much shorter, you may have to loosen and lower the handlebars at most. The only reason we had to disassemble so much stuff on the Banshee was just to get it through the hatch. The dimensions are published on the Polaris site, why not go measure up your Durango?

 

Actually I was measuring my Durango last nigh tat about 11 pm...LOL

It seems like it shoudl fit IF the bars came off/were lowered....WOuld hate to get 150 miles away and find it doesnt...may just take the pickup ...no AC but at least I know it will fit....

I dont know whether to love or hate the web....just when I am feeling comfortable about this bike more stuff comes up....

I searched here and read stuff about broken welds and problems due to water/mud.....

How much of an issue is water/mud?? I mean, what kid isnt gonna run his ATV thru water/mud when he has a chance?? I dont want to be breaking down just because we go thru some water, etc.....

My head is freaking spinning right now what with all of this....plus hoping it fits the boy OK.....so many details.

 

Yes, it is true, Aeon makes several of the Polaris quads, primarily the 150cc and smaller sizes. Polaris isn't the only company outsourcing to Taiwan either. Here's an excerpt from an article I found just last night:

"Her Chee, located in the Yichu Industrial Park in Chiayi County, originally manufactured its own brand name ADLY scooters for export. Drawing upon his almost 50 years of experience in the motorcycle industry, Chairman Chen Ching-Chiang rapidly transformed his company into a successful ATV manufacturer and won orders from both Bombardier and Arctic Cat. Another company Aeon has received ATV orders from Polaris. Suzuki has also subcontracted some of its small ATV assembly work out to Tai Ling and production to some of the ATV manufacturers who entered the market afterwards. In the year 1999, Taiwan exports quickly grew to surpass the 80,000 vehicle mark of which Her Chee and Tai Ling accounted for half."

You can read the entire article here:

http://www.motortrader-asia.com/news...w&news_goid=16

There's plenty of other news coverage about Asian ATV's that contract out to the big name companies....just google for them.

 

Hi all..thanks for the great replies.....I went to look at the bike....round trip of over 300 miles...6.5 hours of my time after work and $75 in gas and tolls....wasted.

The bike was advertised as mint.

It had several issues.....missing all chain tensioner/adjustment hardware...owner kept chain tension by loosening the 4 axle bolts.....oil tank was broken....mounting tab for tank had been weleded twice in two years.....no front brakes.....rear hubs were very loose on the axle...front end was very loose at the knuckles.....strange metallic noise from drivetrain when getting up in speed with me on it (that may be why...I am 235 lbs)....

Before I went out there, the owner had told me that he was on a second battery and it didnt seem to want to hold a charge....and he also told me about the oil tank tab and the rear adjuster being missing.....but nothing about the loose hubs or front end.....

So I just got online and went to a Polaris parts place.....

All told:

Definitely needed:

Adjuster: $45.47 (my cousin says you don't need the adjuster/tensioner and can ride without....but...
Oil tank: $23.99 not bad...that is just the tank..doesnt consider that the tab was welded 2x already...ok I could remove the tank and go premix but....
Fr. brakes:$55.98 for shows....assumes all else is OK....cables seemed ok...probably just shoes needed...ok I could have him ride rear brakes only but....
Rear hubs: $83.18...ok, could leave it be for now until they spin completely...but....
Front end:$117.50...knuckles need replaced...could let it get even MORE sloppy I guess...although it was pretty sloppy...maybe 1/4" of play on both sides at the knuckles? How much would be normal?

"Maybe" stuff:

Rear axle if it needs replaced due to bad splines, another $135.19
Battery: $75...assuming its JUST the battery.....it seemed to crank OK there though and we started it up a couple times...strong cranking....so that may not be an issue....
For that metallic sound and lag, I figured maybe a belt....$42.49

Total of necessary stuff: $326.12
Total of "maybe" stuff: $252.68 if it were all needed....

Grand total is a potential $578.80

And this doesn't account for any other issues it may or may not have. Who knows....I might have spent the $326 on top if the $1100 asking price and had a perfect bike for the next few years...

The bike is worth $1047.00 trade-in and $1400-ish retail sale in KBB.

I could "make do" without ANY repairs besides brakes....wait till it all got worse...but seeing as reliability and safety are a concern....Just too many issues at once....if it were one or two items then I would have jumped on it....but with everything in the mix? My gut said no.

Cool little bike though.

Still not sure about the whole CVT thing for trails, but it moved pretty good once it got me going...of course that was a level grassy yard. 2 strokes sure do stink/smoke though, eh?

Not sure how this thing could wear out suspension parts that quickly though if all they did was ride in their level yard as the owner said....he did say something about some small whoopdeedos, etc.....looking at the 10 year old I'll betcha it was getting jumped "somewhere" without mom/dad knowing....

<sigh> I am bummed that I spent that kind of money on a gamble...but that's what happens when you gamble....(hence why I am NOT a gambling man usually.....)......

Glad I passed I think.

But that bike would fit my kid perfectly I think...I wonder if the Honda is similar in size?

 

zavetsky, I have my 7 y/o on a Honda. He is a tad over 4' and is just tall enough for the quad to fit him. He really needs a bit more lead in his pants, but I am impressed with how he has handled it so far. He even talked his grandmother into a ride last weekend. Once I caught up to him I put the kybosh on that for the foreseeable future though. I like the auto clutch tranny, they rarely break down and are an effective speed limiter while still giving your son more throttle and rpm range while he is learning. At this time I only let my son use 1st and 2nd with the throttle limiter backed most of the way out. He gets to rev the thing a bit, but doesn't develope to much speed just yet[img]i/expressions/face-icon-small-smile.gif[/img] Either way the Pred and TRX are both on the larger size for minis. If you have no MX racing aspirations, I would put a used LT80 on your radar too. They are a bit smaller than the 90 Pred and Honda, have plenty of low end snap, and plenty of dealer, parts, and aftermarket support.

 

Thanks scooter86....

I was considering the LT80 but from what folks say it is a poor suspension by modern terms....

I would also prefer to stay 4 stroke I think.....

What kind of transmission does the LT80 use?

 

The LT uses a cvt tranny like most of the 2 strokes. Suzuki really tuned everything well though, the engine has plenty of low end juice, and the cvt is set up to take advantage of that. The only downfall is that the motor and swingarm all pivot during rear suspension compression. Good in that the chain never really gets a lot of stretching stress from swingarm motion, but bad if your kid is going to try big jumps and such. The Honda doesn't have much suspension travel either, but it does have a conventional swingarm/chain drive setup. I also like the fact that the airbox and filter are set up high, fully enclosed, and under the seat just like the adult quads. I wouldn't worry to much about longevity of the LT motor, these are nowhere near the state of tune stock that you see in the 80cc bikes like the CR and RM's. The little LT seems to be much more tolerant of water and mud than it's cheaper counterparts also.