Ural Motorcycle Fuel

Posted 10/10/2004 12:22 AM (#4963)
Subject: Ural Motorcycle Fuel


Why do Ural motorcycles require premium fuel? You'd think that with such old technology that 86 or 87 Octane fuel would work just fine.
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Huey
Posted 10/10/2004 11:21 AM (#4968 - in reply to #4963)
Subject: RE: Ural Motorcycle Fuel


What is required and what is used is not always the same. Government recommendations or regulations severely hamper the company from printing the truth in all areas of an owner's manual. Urals will run just as good on regular gasoline as on premium gasoline and, depending on where you purchase gasoline, may be subject to pinging if premium is used. Check out the Ural discussion boards and you will find that almost anyone adhering to the higher cost of premium, does so only because of fear that the owner's manual may be giving the straght scoop or that they just never try to find out facts in what they do. Their good sense says it does not really matter in using the lower octane, but still, they don't want to think outside the box. If you have money to burn on the extra, unnecessary expense, then follow the directions. It is really your choice to go that route anyway.

I have an antique car that is in the same category. Many new antique car owners will spare no expense in putting the higher octane gasoline in the tank, thinking they are doing something good for the car. They usually learn quickly that they made a huge mistake and that the car runs best on the crappiest gasoline possible (lower octane). A Model A Ford has almost all the same glitches as a Ural and has the pet cock problems and electrical problems that makes them kissing cousins of a sort in technology.
Huey

Edited by Huey 10/10/2004 11:27 AM
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Hack'n
Posted 10/10/2004 12:01 PM (#4970 - in reply to #4963)
Subject: RE: Ural Motorcycle Fuel



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I've got to agree with Huey. If any vehicle runs on regular (unleaded) without pinging when you throttle up it is a waste of money to use anything more expensive. Regular grade gasoline historically has had better lubrication qualities and leaves less deposits behind than premium grades (less additives, less deposits). The higher octane ratings are only to reduce pinging and spark knock(detonation)which, if severe and prolonged can result in a burnt piston or two. That's not going to happen with your URAL.
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Posted 10/10/2004 12:34 PM (#4972 - in reply to #4963)
Subject: RE: Ural Motorcycle Fuel


I also agree with Huey and Hack'n that it's best to use the lowest octane fuel the motor will run well on. This is the first I've heard that lower octane fuel forms fewer deposits, but I can see how it could make sense. For the same reason it may form fewer deposits, lower octane fuel also has more energy; ie - less additives equals more fuel to produce energy. Contrary to popular belief,premimum fuel means it's resistant to detonation - it doesn't mean it produces more power. It does mean it can be used in a higher compression engine which is capable of producing more power, but that's a separate matter.

However, it is possible for an old technology motor to require high octane fuel if the compression is sufficiently high, the cylinder head design is sufficiently poor, or specified ignition timing is too far advanced. The best way to know if the fuel you are using is adequate is to make sure your motor is in proper tune (valves adjusted, carbs syncronized and with mixture proper, ignition timing spot on, etc.), to load it down, and to take it for a good hard run up a long hill at moderate rpms on a warm day. If it doesn't ping using regular, that's what you'll want to use.

Jim
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retro-rig
Posted 11/19/2004 3:41 AM (#5381 - in reply to #4963)
Subject: RE: Ural Motorcycle Fuel


High octane fuels where/are a transition from the aviation industry. The increase of octane changes the burn duration reducing the likelyhood of pre-ignition and detonation within the cylinder.

If you are fairly competent with a wrench and understand carb jettings & timing values you can make carburator adjustments that weaken or increase your need for differing octanes the biggest variable comes at altitude. If you ride over the continental divide you'll get the idea.

However the average person rarely rides a bike to limits requiring changes in combustion from factory design. But to get an idea of how well the engine is burning fuel examine the spark plug. The simple ceramic & metal device common to gasoline engines can tell you alot about internal engine conditions by the color of deposits upon it alone.

The spark plug can be your first clue to a oil seal problem that you may interpet as a fuel metering problem. But back to grades of gasoline. run the lowest octane fuel specified for your vehicle. You can try lower in a high performance engine just don't crank the throttle for max acceleration. With the added weight of a hack you'll not do the engine any good.
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