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Dr. Dyno's Tuning Tips

When you take your bike to a dyno for tuning by an "expert" why would you leave without it expertly tuned? When a Harley comes off the Doc's dyno, he wants you to have:

  1. Maximum torque and usable horsepower
  2. Silky smooth power at all throttle openings.
  3. Good fuel mileage, typically 42-45 at reasonable highway speeds.
  4. Very little or no decel pop.
  5. Cool running at low speeds.

But what if you can't hook up with the Doc to get your Harley all dialed in? First of all keep in mind that he can give you a doctor's excuse to travel as necessary - as one guy told his boss "to see an out of town specialist." But if you can't make that happen, how do you find a good dyno tuner? They are out there, many at dealers. Here are a few tips to help steer you away from the greedy and find the good. This info applies specifically to tuning fuel injected Harleys but much of it relates to carburetor tuning also.


Ask previous customers how their bikes are running specifically in all five categories listed above. Technical jargon or a blame-it-on-the-customer approach doesn't get your bike tuned. For instance why would a dyno operator push an auto-tuning device that supposedly doesn't require a dyno? Get ready to take the blame for not riding it right.

Another slant on auto-tuning is a feature on Dynojet dynos called "Tuning Link." It supposedly tunes a Power Commander automatically while the operator simply holds the throttle where the screen instructs. It's popular because just about any operator can run it and claim it tunes perfectly. However, in Sturgis Dr. Dyno had the opportunity to make some check runs on a Touring Model Harley on his dyno just after it had been tuned on another dyno with tuning link. At anything over quarter throttle the air/fuel curves on both cylinders were nowhere near smooth or correct. In fact at 80% throttle they were so far off the torque curves had dropouts. Turned out the final run the operator prints for customers doesn't have AFR curves it. Wonder why?

Don't worry too much about not seeing the work actually done. Serious tuning takes a lot of concentration and many very good tuners just aren't comfortable doing it with people watching. What counts is the results.


Although not necessarily bad, a certification just means someone paid the money, took a course and bought the specified equipment. But, as with many jobs, if one doesn't take pride in his work, his boss won't allow him the needed time to do it right, or just plain doesn't have the 'talent', the results may well be disappointing.


A Harley has two cylinders. The air/fuel ratio (AFR) needs to be measured and tuned in both so if the dyno has:


Hype has always come in the form of unrealistic claims.

How about a 50% horsepower increase from pipes, air cleaner and a tuner when the real bump on a 96-inch stock Harley is more like 15-20%? Starting at a stock 62-63HP and ending at 75 gives an actual increase of 20%. That's an impressive bump, one you'll definitively feel. But nowhere near 50%. So, how do you show that on a dyno? Child's play! You fake it. Just make it look like you're whacking full throttle when you're actually stopping at half. The baseline run comes in at 50HP and you've got dyno "proof" of your 50% increase a couple thousand bucks later!

Hype also comes in flashy websites and big show trailers. You may be paying for them but they don't tune your bike. Proper and complete tuning of a Harley even on a fully equipped dyno takes an expert tuner between one to four hours of concentrated work. Yet, one site claims "the man" (who the Doc considers a friend and a good guy) tunes 5,000 bikes a year. Basic math says that would be one every 24 minutes of all 2,000 working hours in a year. So, maybe its a typo because 500 tuned correctly is more realistic, but 5,000 looks impressive on a website.


Even with a two-channel AFR setup, tuning a Harley takes well more than a few runs and a few minutes. But some dyno operators may sell and install a tuning device, and then instead of actually tuning with it, they "use their experience" and just "try" a few different maps, saying this one is the best or makes the most horsepower. It's done for two reasons, time and money, specifically more money in less time for them. They already made their money on the sale so why not get on to the next customer.

Fixed price for tuning or having tuning included in the price of a build motivates the tuner (or his boss) to shortcut the tuning process to maximize profit.

Watch out for horsepower kings. While every bike should make the maximum horsepower it's capable of, over-emphasizing maximum horsepower or torque is a trick. A few tweaks at full throttle is the easiest part of tuning. What they're really doing is diverting attention from the time-consuming midrange tuning that makes your bike a pleasure to ride.

Avoid a "quick" tune. That's just an excuse to not get it right.

Don't accept any printouts w/o an AFR graph. Likewise don't accept AFR graphed on a 0-20 scale. That compresses the data so much almost anything looks good. Extra hint: Ask for a graphs of the both cylinders at 20 or 40% throttle with AFR on a 10-18 scale.


Supposed violation of warranty is a panacea used to justify almost anything these days.
In the case of adding aftermarket tuning devices to your Harley it's often used to sell only Harley products such as the SEST with the claim that non-Harley products like the Power Commander will void the warranty. In actuality the opposite is true. A Power Commander and many other add-on tuning devices can be removed without any trace. They leave no electronic tracks in the bike's ECM. All ECM tuners such as the SERT and SEST do. Just read the "Warranty Implications" on the box. So, if a dealer is pushing that non-truth, what else is he pulling?

Bottom line:

Ask those who want to tune your bike with their device, "What is the total investment, both in time and money, that will guarantee that no one will be able to tune my bike any better?"

Page updated Monday, March 4, 2013 8:28 AM