ATVConnection.com

Dear ATVC:

It seems like more and more ATVs are coming with fuel injection. I’m not sure how I feel about all this high tech, computer controlled stuff. Are there any real advantages to fuel injection or is it just another reason to have to take my ATV to a shop when it needs repair?

There are certainly some advantages in the real world- namely saving you from having to make carburetor adjustments to compensate for things like elevation, temperature, humidity and modest modifications. Additionally throttle response across the entire RPM range is typically improved and fuel injectors are less susceptible to fuel varnishing that takes place during long periods of inactivity/ storage.

Of course, like most technology advances, there are some downsides to consider as well. Among these the need for a battery, fuel pump, thicker gas tank, high-pressure fuel lines, sensors, larger ECU and throttle body- substantial weight gains are a given!

And unlike a carburetor, which is an entirely mechanical device, fuel injection relies upon fragile electronics and sensitive connections. Your ATV’s computer receives data from sensors reporting the position of your throttle, intake air pressure, water temperature and so on, which allows for some automatic adjustment when installing a new exhaust for example. Surpass that range, however, and a laptop with custom software (or a dedicated tuner module) becomes the only way to compensate; a considerably pricier investment compared to brass jets of a carburetor.

In all many manufacturers have weighted in on the pros and cons of each fuel delivery method and the writing is on the wall: The carb’s days are numbered.

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Dear ATVC:

Back in the two-stroke days, I used to freshen up the top end of my quad with regular frequency but quite frankly, the complexity and cost of a modern four-stroke engine intimidates me. Is there any way to know when I’m due for fresh rings without actually tearing down my top end?

 

Absolutely! Begin with the exhaust pipe. Is it smoking like the ashtray at a smokers anonymous meeting? There’s your first indicator. Additionally check the joints and sealing where the head pipe meets the manifold and where the pipe meets the muffler. Abundant oil collecting as these junctions is also not a good sign for the health of your rings.

Like with any engine, ring tolerance (along with the state of tune of the piston) dictates compression. Hence if your ATV’s compression suddenly drops, it’s very likely worn rings are the culprit.

But above all else, keep an eye on your engine’s oil consumption. Check the oil breather tubes before and after a ride. A little moisture here is normal but dripping/ leaking oil breather tubes is another sign of oil blowing by the cylinder seal being created by the piston’s rings. If you’re noticing you need to add oil after a couple hours in the saddle, you’re likely due for a fresh top end.

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Dear ATVC:

My quad’s rear shock feels really springy- it still seems to be working but the rear of the machine bounces more than I remember over rough terrain. My friend says it means the shock is blown and needs to be rebuilt. I thought a blown shock wouldn’t work at all. Please help.

Sadly we’re inclined to agree with your friend on this one. To understand why a blown shock turns even softer and bouncier than a properly functioning one, let’s take a moment to examine what’s going on inside your ATV’s shocks.

Shocks absorb impact by using the flow of fluid (oil) through stacks of washers that act as valves. When a shock is new (or freshly rebuilt), the system works smoothly. However, like all oils, shock fluid begins breaking down over time. As shock fluid degenerates, it becomes thinner and hence passes through the valving with less resistance than it should.

This is critical because the damping circuits (valves) inside your shock are what provide the resistance not only to impacts causing the shock to move in the first place but also to keep the shock’s spring from compressing and expanding wildly. So why have a spring at all if it’s oil doing the absorbing? The answer is rebound; or the force that allows the shock to extend after it has been compressed. Without a spring, your shock would only work the first time it was compressed.

In addition to the shock’s fluid breaking down inside, the outside of your ATV’s suspension is dealing with all sorts of nasty conditions each and every time you ride. Dust, grime small rocks and sand gather up on the shock bodies then get pushed into your shock’s rubber seals. Acting as gritty sandpaper, these unwanted materials breakdown seals and wipers over time as well, often resulting in the shock’s internal fluid leaking out.

The reason a blown shock feels suddenly softer is that the fluid-driven damping circuit is being bypassed entirely due to one (or both) of the situations described above. In other words, your machine is in fact riding on the spring and the spring alone. No oil damping absorbing the terrain (compression) and likewise no oil damping to slow down the spring’s return expansion (rebound).

Higher end shocks can be rebuilt (oil change, fresh seals etc.) but many budget-friendly ATVs (including minis) offer non-rebuildable units as a cost shavings measure. If that’s the case with your particular quad, replacement is the only option.

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