Ride                                                            H-D           AutoLite        Champion       Accell

All 45's thru '73                                             3                   N/A                 D16              N/A

Ironhead XL '57-'78                                      4                  996                 H8C             2402

Ironhead XL '79-'85                                   4R5                4123            RL82YC          2413

Evolution XL '86- present                         6R12              4164             RA8HC          2418

Panhead & Shovelhead '48-'74                3-4                4275             J12YC            2401

Shovelhead '75-'81                                   5R6A              4265            RN12YC        2410A

Shovelhead '82-'84                                   5RL                2585             RN13LYC      2417

Evolution BT '84-present                          5R6A             4265             RN12YC        2410A

When you time your vehicle, you have 4 things to consider: Altitude, ambient engine temperature, octane rating of your fuel, and ambient air temperature. Remember this: In a higher altitude, you can get away with a lower octane gas. In colder temperatures, you can use a lower octane gas.

In fact, I consider a lower octane gas *better* for my bike in the winter time. Why? High octane gas promotes cooler running of your engine. In the winter, when your bike may *never* reach proper running temp (190 degrees) *all* season, it's better to use a gas that may make your bike run at 160 degrees as opposed to a higher octane gas that will only allow your bike to reach 130 degrees. That's waaaay too cold an engine temp to travel on IMHO.

If you travel, you will note that Denver sells fuels as low as 84.5 octane. You'll never see that in Dallas, because the lower altitude promotes a quicker burn in your car. High octane gas has a slower "more controlled" burn. Soooo...you can regularly find 94 octane gas in Dallas, because at sea-level, where gas burns faster than 1 mile high, 94 octane will keep your car from "pinging". Pinging is when the spark happens too quickly in relation to the position of the piston. If your car pings on 88 octane in Dallas, chances are you can fill her up with 94 octane, and the pinging will magically go away.

Also, a hotter engine will be more likely to ping than a cooler one because fuel burns faster in a hotter atmosphere. You can start your car, drive around the block, and she won't ping. The motor is still cold. However, when the car warms up, you may develop a pinging condition due to the hotter burning atmosphere created in your cylinder. On a Harley, where the engine runs anywhere from 130 degrees to 290 degrees, you have to give ambient engine temperature waaaaay more consideration than a car that will run at 210 degrees all day long come winter or summer.

So we have:

Hotter air temp = hotter HD engine = quicker burn
Lower altitude = quicker burn
Lower octane = quicker burn.

Cooler air temp = cooler HD engine = slower burn
Higher altitude = slower burn
Higher octane = slower burn
Pinging is caused by too quick/advanced of a burn.
Now, based on this formula, I will give you the easy, easy, easy accurate, accurate, accurate way to time your bike. A fringe benefit of my timing method, is it considers *all* factors. Using a light and a timing mark barely comes close.

Set your timing close enough to TDC that you can start your bike and ride around for a while. Let the bike warm up to 160 degrees if possible. If it's really cold outside (below 40 degrees), you may never get above 130 degrees operating temp.

If the ambient temperature stays below 60 degrees outside, use regular unleaded. If it the ambient temp hovers around 70 degrees, use medium grade fuel. If it stays over 80 all the time, use premium gas. I do not use octane ratings here as I don't know what altitude you live in. I wouldn't go below 86 octane. If you are at 5,000+ ft. above sea-level, anything over 91 octane will be a waste of money.

Once your Harley has reached it's maximum running temp, get on a straightaway that's *not* downhill. Flat is okay and up hill is okay. Do 50 mph in 5th gear and accelerate using 1/2-1/4 throttle. Your bike's motor should be running *around* 2,200 rpm at that speed in 5th gear I believe.

Does your motor ping? If it pings *slightly*, you're right on the mark. If she pings horribly, you need to retard your timing (rotate timing plate same direction as engine rotation). You can pull over and do this by the side of the road. If she doesn't ping at all, advance your timing a little. Now I'm talking about 1 degree intervals here. That would be about 1/16th of an inch as you look at your timing mark. If you have no timing marks on your timing plate or the inside of your nose-cone, make some. Just scratch them in.

With this method, if you use low-octane gas when it's cold outside, and high octane gas when it's hot outside, your timing will be as close to perfect as present-day mechanical timing advance mechanisms will allow it to be.

If you travel to a different, lower altitude, pinging will get worse. Use 94 octane gas. If you still continue to ping really bad, pull over and retard your timing just 1 degree. Remember, too much pinging is bad for your motor and *could* damage it if you continue to let the motor ping all the time. A *little* pinging is okay and actually tells you that you have reached your optimum timing.