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Jet Tuning
Tips for Two- and Four-Stroke Engines
If your quad is sluggish when your thumb hits that throttle, and you suspect jetting issues could be the culprit, try these fuel screw, air screw, and pilot jet tips to diagnose the problem. The working range of the fuel screw on a four-stroke engine is one to three half-turns out, while the airscrew on a two-stroke engine has a working range of one-and-a-quarter to two half-turns out. If adjustments outside of these working ranges improve throttle response, the culprit is the pilot jet. If you tweak the fuel screw to the upper end of the working range, richen the pilot jet; if you’re working on the lower end of the range of the fuel or airscrew, lean out the pilot jet. Here’s an easy tip to locate the necessary parts: Airscrews are always located on the airbox side of the carburetor slide, while fuel screws are located on the bottom of the float bowl on the engine intake side of the carburetor slide. Most fuel screws are plugged from the factory for EPA regulations, but feel free to take the plug out and tune your quad. It will really appreciate it!
Stiction Business
Measuring Stiction the right way
Measuring stiction is a great way to determine when your quad’s bearings need to be replaced or serviced. To measure stiction, lift up on the rear grab bar and let it drop. Now take a measurement from the floor to the grab bar and write down the value. The second step of the process is to push down on the rear grab bar a few times and let it rest, then take another measurement from the floor to the grab bar–write down this measurement and figure out the difference between the two measurements.
Do this often and you will notice when your quad’s linkage bearings need to be replaced. As the stiction value increases, it shows that bearings are getting dry and are in need of grease. In a perfect world there would be no stiction, but there is always going to be drag affecting bearings, so start with a fresh greasing, take the measurement, write it on a notepad and put it in your toolbox for future reference.
Chain Reaction
Proper chain tension for your quad
Are you unsure if your quad’s chain is too loose or tight? Here is an easy test: Grab a ratcheting tie-down and put it around your quad’s axle carrier or axle and run it to a sturdy place on the frame of your machine. Slowly ratchet down the tie-down and watch how the chain becomes tight and goes past the “tight spot (it may help to soften up the compression before you do this). Once you have gone past the tight spot, you can recognize whether the chain was too tight or loose. Once you get the chain to have a little slack at the tightest portion of the stroke, you are ready see how many fingers it takes to tighten the chain with the suspension. Once you figure this out, you will always know when the chain is too tight or loose.
Non-Loctite Insurance Policy
A little prevention to keep bolts bolted tight
The desert dishes out a lot of abuse, so before hitting the dunes (and we mean literally hitting the dunes) check that every bolt is tight and stays that way. Our friends at CT Racing showed us a cool way to keep bolts in place without using Loctite. 3M makes a product called Super Weatherstrip Adhesive (yellow) that will do the job of Loctite but won’t strip out the threads on those fragile 6mm bolts and nuts. With the bolt or nut in place, simply put a strip of the adhesive from the head of the bolt or nut to the plastic or metal that it attaches to and let it dry. Simple. Now the dunes can’t dish out anything your quad’s bolts can’t take…well, except for maybe a 20-foot drop off of a razorback.
Keep It Cool
Proper antifreeze mixture is important
If you are running straight antifreeze in your quad, there is a good chance that it’s causing the engine to run hotter than necessary. The best type of antifreeze for your quad with the best cooling properties is any glycol-based mixture. Some bottles come premixed 50/50 with water, but others don’t, so check on the label to find out what you’ve got. If you have to mix, use only deionized water (because it is free from ions that cause engine corrosion). Don’t skimp on this! Say it with us: “deionized water. Good.
A 50/50 antifreeze/water solution will protect your quad’s engine from boiling over, as well as keep it from freezing in the winter. Having the mixture antifreeze heavy makes the engine run hotter, while running the mixture water heavy increases the chance of the solution freezing in the winter.
Two-Stroke Myth
Breaking down the premix rumors
There is common belief among two-stroke riders that premix oil inhibits power, and leaner mixtures produce the most power. This is not entirely true. The ring needs oil contact to keep the ring stiction high. This stiction from oil contact is a big factor in compression, which directly relates to power output. Also, there is never enough oil in the two-stroke fuel mixture to completely satisfy the needs of the bearings in the engine. Cranks and main bearings would love to be in an oil bath like a four-stroke engine, but must rely on fuel delivery and strong oil molecules to produce long-lasting lubrication–for this reason, the highest grade of pre-mix oil is recommended for maximum engine life. We also suggest sticking within a 32:1 to 40:1 ratio for your two-stroke.
The Dirty Cycle
Clean air equals happiness all around
We always harp on this topic, but here is another reason to keep your quad’s air filter clean: On a two-stroke engine, any dirt that gets through the filter and into the engine passes through the engine’s crank and main bearings, scuffs the cylinder wall, and pits up the top of the piston. Essentially any dirt that goes through the filter hurts the entire engine. The common problem here is that most riders replace the top end to fix the damage, not knowing that the bottom end has an equal rate of failure because of its contact with contaminants that creep in through a dirty air filter. It is possible to measure rod movement to determine the extent of the damage to the lower end, and the owner’s manual should have the measurements for your quad.
The effects are a little less severe on a four-stroke, because the dirt doesn’t get into the bottom end of the engine, but it will surely do some damage to the valve train. The moral of this story is to keep a second clean and oiled air filter in your riding kit, because it will come in handy. Your quad and its clean engine will thank you with lots of power.
