Premium Fuel -- A Burning Question!

So, I am currently in the final phase of restoring my non-KZ motorcycle ('69 Sprint). The manual calls for "Premium ethyl gasoline from a reputable service station". No problem finding the fuel, but why for this motor? It is a single cylinder, 350 motor with a compression ratio of 9:1. It is my understanding that high octane fuel was for higher compression engines where pre-ignition could become a problem. I have had no better results from running premium fuel in my KZ for FJ than regular fuel. I have read that you shouldn't run high octane fuel in an engine that requires due to incomplete combustion and such.
Am I missing something?

nope,long as it dont ping dont worry;)

cafekz750 wrote:

So, I am currently in the final phase of restoring my non-KZ motorcycle ('69 Sprint). The manual calls for "Premium ethyl gasoline from a reputable service station". No problem finding the fuel, but why for this motor? . . .Am I missing something?

I'll ask the only guy I know that had a Sprint the next time I see him, but I think premium ethyl gasoline had LOTS of lead in it.

Can you get leaded fuel?

The lead was supposed to help protect the exhaust valve seat from erosion.

Erosion was a problem until engineers figured out how to put and keep hardened seats in place.

I don't know whether a '69 Sprint has that technology. Maybe the folks that do know know the Sprint doesn't have the seats, hence the need for the lead.

Maybe you need to ask politely in a harly forum.

Technology and a Harley...
The Sprint requires leaded gasoline due to the non-hardened seats. I currently add lead substitute to every tank to compensate (as well as Seafoam and octane booster).
So, go to gas station, fill up and pull out the miracle motorcycle tonic and add the appropriate amount. It's kind of a pain.
If I could drop the octane booster and the premium fuel, life would be easier and cheaper.

Post edited by: cafekz750, at: 2007/07/16 15:38

Hardend valve seats showed up in 74 so anything before will require lead. The premium fuel back then had the most lead. Fuel now a days have no lead so you will need to add it yourself.

cafekz750 wrote:

. . .The Sprint requires leaded gasoline due to the non-hardened seats. I currently add lead substitute to every tank to compensate

I don't think you need octane booster and everything else necessarily. Just the stuff that turns to poison vapor.

:sick:

Ask around at some of the automotive machine shops. It might not be that involved to get one valve seat (or two) installed in an air-cooled head. They have the tools to replace them if they fail. It seems logical that they could come up with something thet might inprove your one-lunger. Post '74 parts.

I think some of the Harley motors use Chevy 350 pistons, with minor modifications. It could be that later GM parts are drop in for the valve upgrade.

Is the Sprint a pushrod motor?

Valve height might need to be a little longer than stock. Head diameter might have to be smaller, if the head wont support the extra milling necessary for the seat.

Do the research and ride the bike until you get the answers that allow you to tame the wild horse. When it becomes time to decoke the head to remove the lead deposits, then you can upgrade, since it will be easier than grinding down pencils to extract the lead.

:woohoo:

Post edited by: KaZooCruiser, at: 2007/07/17 09:24

Thanks for the info so far. It is good to know that the premium leaded fuel had the most lead in it. It makes sense for the manual to suggest it since it is a European motorcycle.
For those who don't know, the Harley Sprint was actually and all Italian made motorcycle made in Italy in the Aermacchi factory and sold as Aermacchi-Harley Davidson everywhere else but in the states (and perhaps Canada?). I have attached a photo for those who remember the bike and those who might want to know what the heck it is.

I am thinking about switching to regular fuel on the next fill up and dropping the octance booster. If I here a ping, I can always go back to what I was doing.
Also, the Sprint is a pushrod motor and they stopped making them in 1974. They still race them so after market valves and seats are an option but cost money...

Post edited by: cafekz750, at: 2007/07/17 14:12

I would not use the octane booster, it dosent mix even in the gas, so you dont know what you are getting, I blew a race car up using the crap, figured it out during the tear down, the lead additive is prob ok, since it was used to lubricate and doaent have to be that consistant

cafekz750 wrote:

. . .For those who don't know, the Harley Sprint was actually and all Italian made motorcycle made in Italy in the Aermacchi factory and sold as Aermacchi-Harley Davidson everywhere else but in the states (and perhaps Canada?). . .

Italian craftsmanship and the Harley nameplate.

The beast of both worlds.

:laugh:

Post edited by: KaZooCruiser, at: 2007/07/17 17:32

thats a nice looking little bike.

Say after seeing that pic I know a guy who has one. He lives in berea ohio. I remember him filling up at a gas station and adding a lead substitue to his tank. He uses I think the CD-2 lead substitue. The same thing I use for my Kaw. He puts 1 ounce per fill up, I use two ounces:P . The lead lubricates the valves, valve stems, seats, and helps the valve stem seals from leaking.
I put it all my vehicals except the ones that have catalytic converters, they will clog:sick: :pinch:

cafekz750 wrote:
. . .For those who don't know, the Harley Sprint was actually and all Italian made motorcycle made in Italy in the Aermacchi factory and sold as Aermacchi-Harley Davidson everywhere else but in the states (and perhaps Canada?). . .

Italian craftsmanship and the Harley nameplate.

The beast of both worlds.

Yeah, perhaps not the best of the motorcycle industry at the time, but it is a simple bike and you can fix everything with a flat blade screw driver and an adjustable wrench. :laugh: And since it is Italian and HD, after every ride you get to use both.

thats a nice looking little bike.

Thanks, I have to agree. My father bought it new in 1969 and it was the bike I got my first ride on. Been hooked ever since. I remember holding tight on to my father worried about falling off...it is all relative. After I rebuilt the motor, my father and I would go out for ride taking the Sprint and my FJ1200 and swap half way through. From Sprint to FJ was quite a change...

...I know a guy who has one. He lives in berea ohio. I remember him filling up at a gas station and adding a lead substitue to his tank.

Yeah, that is the price I am willing to pay until something breaks and I have a good excuse for a valve job, piston...:whistle: :evil: