AIR BOX HYGIENE: MR KNOW IT ALL
Dear Mr. Know-It-All,
I ride in the desert, so both my bike and I suck a lot of dirt. I think I could grow corn in my airbox, and I have come up with no good way to clean the airbox of the dirt and slime that has stuck to everything. I end up dropping crud in the air boot, and I’m nervous about sucking it into my motor. How do you handle this?
Well, my stymied friend, you can always take the time to remove the airbox, clean it properly and then reinstall it. Or, get this simple yet incredibly effective airbox cover from Twin Air. It pops in place of the air filter and allows you to shoot some degreaser or bike wash into the zone and then blast it with a pressure washer. Check with TwinAir.com for a fitment chart.
NAILED
Dear Mr. Know-It-All,
I’m new to dirt bike riding and spend my dirt time riding trails. Two of my last few rides have been cut short when I got a flat front tire. Besides nearly killing myself trying to get back home with a front end that went anywhere but straight, what is the best way to not get a flat? I don’t have a lot of money, and I read about these solid tubes, but they’re way out of my budget.
Tim Debrott
via [email protected]
Mr. Debrott, welcome to the most satisfying of all outdoor activities! Naturally, having a properly setup vehicle and the ability to work on said machine is paramount to a palatable experience. My sage advice is such: Learn the basics of maintenance and repair where fixing a flat and changing tires are talents that you will need repeatedly. So, owning proper tire irons and the tools required to fix your dilemma are key ingredients. I say this simply because, with the confidence to do this task yourself, you can carry the tools necessary to perform the job on the trail. It’s not fun, but prior to the introduction of the foam-tube insert, every savvy dirt pilot either rode with a deflated front meat or repaired it.
That said, the cheapest way to avoid a flat caused by a nail or thorn is using Slime. You insert the proper amount of this goo into the tube, and if invaded or pierced, it will seal off the wound. Unfortunately, a major cause of flat tires is the pinch flat, where the tube gets pinched when the tire compresses on a big hit. Slime is no help here.
Until you can afford a set of Nitromousse foam inserts (my personal favorite), carry either a flat repair kit or a tube with you. Many companies have CO2Â cartridges to inflate the tube, but I have also carried a handheld bicycle pump in my drink system. Carry two small tire irons, as toting heavy items weighs down the fun factor of riding.
Being self-sufficient on the trail is a huge step in enjoying and embracing the off-road world. Good luck!
TWO-STROKE VERSUS FOUR-STROKE
Dear Mr. Know-It-All,
Please share your infinite wisdom and deign to respond to my simple query: Why is the conventional wisdom that two-strokes are easier and cheaper to maintain than four-strokes?
My experience has been the opposite. I have a 2016 Husky FE350 with 490 hours on it. Valves have never needed adjusting. Bottom end and transmission are all original and still tight. Fuel and ignition have been super reliable at all elevations and temps.
I also have a 2020 KTM 250XC TPI with 300 hours on it. At 295 hours, the two-stroke started smoking badly. The crank seals were shot, and gear oil was being sucked into the bottom end. So, the bottom end is getting new bearings, a crank rebuild, etc. Plus, I have needed to replace the TPI sensors every 100 hours to minimize run problems.
So, in my experience, four-stroke bottom ends last twice as long as twostroke bottom ends. And, four-stroke fuel injection is super reliable, but not on the two-stroke. Four-stroke heads and valve trains are very trouble-free, too.
Both bikes have had the piston and rings replaced and cylinder re-plating at similar normal intervals. I get that a carbureted two-stroke would avoid the TPI sensor and fueling issues.
But, the bottom-end lifespan on the two-stroke seems to be half that of the four-stroke.
So, again, I ask, why is the conventional wisdom that two-strokes are easier and cheaper to maintain than four-strokes? Thank you.
John Barnhart
via [email protected]
John, this has been an ongoing debate for decades. We at Dirt Bike are spoiled, as we’re presented with a constant flow of new machines to test. We got in touch with Dick Wilk from Dicks Racing, who has been building engines for 40 years. He’s both a two-stroke magician and a four-stroke aficionado, and here’s his take on the two-strokeversus-fourstroke rebuild drama:
“Conventional wisdom applies to a time before fuel-injected two-strokes. Back then, it was easier for the average owner to replace a top end and less parts were required. Modern smokers have become much more complicated but are still easier to work on than fourstrokes. The average person does not have the knowledge to do a four-stroke valve adjustment let alone replace the piston. The highest wear item on a four-stroke engine is the head, which includes the valves, springs, guides, seals, camshaft, cam chain and bearings. Not many shops can properly rebuild heads, so a specialist is required. The fact that your four-stroke engine hasn’t required service means you haven’t sucked any dirt and you don’t rev it too high. If you did, your story would be different.
“As for the lower end, two-strokes do require the crank seals to be airleak-free; four-strokes not so much. The fact that your seals lasted 300 hours is nothing to complain about.
Both engines have fuel pumps, injectors, ECU and sensors, all of which can be problematic. The bottom line is the cost to rebuild a four-stroke is much higher than a two-stroke due to the greater number of parts and the labor required to do the work.”
email: [email protected] | mail: Dirt Bike Mr. Know-It-All 25233 Anza Dr. Valencia, CA 91355
