In this case, by pushrod, they mean an engine that has the cam beside the cylinder, with 'pushrods' actuating rocker arms, controlling the valves, as opposed to one with an 'overhead' cam, or a cam above the head, often actuating directly on the valves, in the case of a 'dual overhead cam' system. The overhead cam advantage: less mass to move to actuate the valve, allows for higher RPMs, and supposedly greater valve opening/duration. Dis-advantages include, a pain to adjust (if you never worked on a shim & bucket system, you aren't missing much), greater complexity in the sense of difficulty to rebuild, and lastly, the heat from combustion tends to go 'up' right into the cam area.

Advantages of a pushrod design are: simplicity (there may be more moving parts, but almost anyone can figure them out & get them set right), ease of valve adjustment (the 700 is even self-adjusting - most others use a simple threaded stud/locknut arrangement), reliability (cam is out of the heat). Dis-advantages are somewhat lower max RPM, and some say they don't 'breathe' as well in general. There are also a few intangables, such as cooling efficiency, center of gravity, etc.

 

Even from my drag-racing days, big motors=big power (eventhough I raced small blocks) The people that don't have it (big cubes) always want it, and they'll start flapping the gums to divert attention from their inadequacies (better stop there....awful vocabularic stretch). Let 'em talk, and just leave 'em in the dust!!

Ken

 

Why would Polaris use push rods anyway, it doesn't give it more power,the cam isn't going to run cool enough to make a big difference,only two valves per head so I believe they done it because they needed that extra room on top of the engine,the overall height is 47 inches,6 inches taller than the other big 4x4s. Push rods doesn't make it bad,there was a reason for it.

 

I'm in complete agreement with Farmr 123. Why, oh why, do the two Hi-Torque ragazines sell one system as being "reliable" and "low maintanece" and "proven" (Honda) and label the other design as being "low tech" and "dated"? Well I'll tell you why.

The two Hi Torque ragazines are notorious for their view as Japanese lovers. If anything comes from Japan and they advertize in their magazine, it's the greatest thing since sliced bread. I'm sure if you asked them, they'll say Japanese invented sliced bread too (or if they didn't invent it, they made it better). They are what is know as Xenophiles. The Japanese can do NOTING wrong in their eyes, while us lazy Americans can do nothing right when it comes to building quads. This is the whole unvarnished truth.

Also because they have this notion that Japanese machines are better, they don't bother to test machines any more. How many times have you read through an article of theirs and found GLARING mistakes where they listed last years specifications, glanced over new designs and formed the wrong conclusions just because they didn't bother to test the machines they were writing about.

One of my favorites was: " You'd think that with the bigger engine, the Sportsman 700 would be the fastest." "But that isn't so because it uses an out dated pushrod design and two valve motor." C'mon guys! If you'd have bothered to look at the specs, you'd have noticed that the Sportsman 700 is hauling around 140 lbs. more WEIGHT than the Prairie. Could this be the reason why the 700 is slower? The Sportsman motor DOES put out more horsepower than the Prairie motor. It just doesn't put out THAT much more that it will overcome it's 140 lb. weight disadvantage over the Prairie. DUH!

Also, does any one here want to read about a quad who's design hasn't changed since the 1980's? I sure don't! Yet they keep on publishing endless articles about the Banshee, Blaster, Warrior, 300EX and Mojave. There are so many other new quads out there, try testing them (assuming they actually test them in the first place). After subscribing to these "rags" for several years I think I've seen just about every 250R variation in the country. They'll usually test some guy's GNCC quad in the sand dunes and complain about it being too narrow. Or some machine that you'll NEVER be able to own (VFR 503 quad).

Between the biased "testing", the endless amount of advertizements (Dirtwheels is starting to become the "GQ" of quad mags)the lame reviews of out dated machines (see above paragraph), ludicrous tests of other people's machines and the machines you'll never be able to afford or own, you start to get the picture of why I don't trust them as much as some do. This is probably why I spend so much time here as opposed to reading their "fish wrap".

 

Hey Rick,

Nice to see you post. My 400's doing fine, and we're going riding tonight. It's a huge group going....15+, and lots of Hondas. I love it when Hondas go with us.

I agree with everyone's posts here, and the mags are biased towards the japanese quads. I believe that the 700 is really doing a good job to put out more hp than the Prarie 650, since the 650 has most all of the "technological advances" that the 700 is lacking.

The reason that Polaris used this particular engine is that Polaris is much like other American manufacturers........in that they try to keep their cost down by using as many identical components throughout their entire lineup as possible. It didn't take nearly as much engineering to develop the 700 engine(based on the snowmobile engine) as it would to come up with a completely new design, and the 700 yielded the hp output Polaris wanted. Most of the parts for this engine were already in production, and this is cost savings to polaris.

I will say though, that the sp700 is a major departure from most previous Polaris machines. Most of the driveline is different, along with the frame. There are still many components that it shares with other polaris machines, however, it has lots of changes incorporated into it. I was glad to see that Polaris finally put a larger radiator on one of their quads, along with a better cooling fan.

Sorry if I deviated too much from the topic.

Waylan

 

Trailhog, you make a good point, about keeping the overall height of the engine less.
I WOULD like to note, though, that I have personally had 2 OHC engines quit on me due to overheating of the cam. One siezed the cam completely (the oil just got too hot) and cracked the head. The other galled the cam, causing it to run VERY badly. Don't get me wrong, for running around they were fine, but when you work them too hard, the cam WILL overheat. I blame the dealer for 'swearing' that I would have NO problems with either machine due to overheating, even after I told him EXACTLY what I intended to do with them. He was just too eager to sell what he had on the showroom, as opposed to possibly losing a sale because he didn't have what I needed on hand.

 

Honestly, most folks cannot think for themselves. They want to be accepted and to be accepted they get what everyone seems to think is popular. Just like the "Media" shapes our news, they shape our marketing too. The Honda's, Yamaha's, Suzuki's, Kaw's, etc... spend BIG BUCKS advertising and spinning the media. They have to for their large sales. They are also 20%-50% higher in price.

For instance, when I was getting my quad I saw the beauty in the simplistic design of the Scrambler 400. I never would of bought the 500, although they are great quads. The 400 was:
1. 2 cycle.
2. Had reverse.
3. Was a big bore that modded to outragous hp VERY INEXPENSIVELY.
4. Liquid cooled.
4. Weight was 480 counting what I knew was a 1000 lb. muffler. (I could lighten).
5. Years of history and success.
6. Had quality companies like HPD and RCR behind them for mods.
7. Did everything very well, but wasn't specialized (MX yuck!!).
8. Was American and my money stayed home (USA).
9. Rides very good.
10. RELIABLE.
11. Priced very low ($4200 vs. Raptor $6300).
.
.
.
.

I almost bought a Raptor, but they failed points 5, 6 & 10 (I was within 2 minuites of cutting the check). It also failed some other points I was willing to let go but not 5, 6 & 10. In fact I laugh out loud everytime someone starts their mindless whining that Polaris isn't reliable and is poorly designed. Shoot, can anyone say that owning a Raptor?? Remember I wanted a Raptor, but I had to think for myself.

Some things I disliked about a Raptor:
1. It wasn't any shorter in seat height than a Scrambler.
2. The transmission (1, 2 & 3) gears will blow out.
3. The valves in the head are mushrooming with wear. I know this for a fact.
4. Their rear axles are prone to breaking.
5. The swing arm will fracture with heavier riders (I weight 240 lbs).
6. Clutch basket blowing in high revs after missing gears with the poor tranny (see point #2).
7. Nylon gear around clutch basket that drives the oil pump strips out after point # 6 happens.
8. VERY EXPENSIVE TO MOD.
9. VERY COMPLICATED to work on.
10. Blow the carbs off a lot.
11. Yamaha won't pay for repairs, at BEST you might get them to replace their defective parts. No labor included (if out of warranty).
12. Is approx. 60-80 lbs lighter than the Scrambler worth $2100 more??? (Scrambler stock weights 480 vs Raptor 404 lbs)

I could go on and I am not dis'ing the Raptor. Just facts to consider before buying. Heck if they get their reliability down and such, they will have the all time reputation of the Utlimate MX quad, replacing the 250R. They are great quads, but they have their "issues".

The small air cooled, under powered, no reverse, great handling Honda 400EX never enter my mind. I wanted more.

Plus, there is pure joy when I ride my "Farmer" quad with steal toe boots, jean coat, no name helment, jersey gloves, painter pants, stock looking Scrambler with a rack on the back, some cheap looking pipe while schoolin' some of those snobs. They got great bikes, but they gotta earn it with me.

Zoom, Zoom
Chunky

PS I hate picking up those MX quads over the logs, help pushing them back (no reverse) and such everytime I Cross Country.

 

So, if I understand correctly, the low tech push road design utilizes a cam next to the head with short push rods??? If this is true, how is it different from the Rubicon?

Greg

 

The main difference is in the manufacturer's name on the gas tank. Other than that, they really are of a similar design, except for the # of cylinders on the 700. Maybe it is more 'high tech' because it sits 'sideways' in the frame???? [img]i/expressions/face-icon-small-confused.gif[/img]

 

Farmr123 and gregsims,

The sideways mounting that honda utilizes does create a more efficient driveline, as fewer angled power transfers are used, however, it would not be advantageous for polaris to mount thiers sideways, since they use the belt drive.........much like Honda doesn't turn their engine sideways for their chain drive models. So, unless Honda uses more valves, their engine is no more high-tech than Polaris' 700. The tranny may be a different story, but we're talking engines here. One thing I'm ready to see is for Polaris to go to fuel injection........on the 700, as well as the 2-stroke 400. They have the technology sitting there, and I would pay a couple hundred dollars more for it. I was talking to my cousin last night, and he actually brought up the fuel injection......his comment was how a even a bicycle manufacturer with their first dive into atv production used fuel injection. This is where all the major manufacturers are falling behind in technology. With the injection, optimal jetting would be achieved at all times, making the machines more reliable, especially when aftermarket add-ons are utilized. Just my opinion.

Waylan