Low grade fuel......also high altitude - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 12 (permalink) Old 06-25-2010, 01:30 PM Thread Starter
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Low grade fuel......also high altitude

Hi,

Has anybody used these bikes with low grade fuel? I understand the engine runs at quite a high compression ratio. Will this cause problems if the bike is used with low grade/low octane fuel?

Also, at what altitude might I start to find problems with the bike?

Cheers,

Gabriel
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post #2 of 12 (permalink) Old 06-25-2010, 01:52 PM
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The vn750 has a 10.3:1 compession ratio, and is designed to run on regular grade, 87 octane gas. This seems to me, to be quite high compression for regular gas, but I have seen reports here of the vn750 running worse on higher octane mid grade or premium gas.

What grade/octane level do you expect to find on your adventure in Asia? Lower octane will cause pre-ignition (pinging) at some point.

What altitude will you reach too? If your bike is tuned to run near sea level, the thinner air at altitude will have it running rich I think.

Sorry I can`t offer any any more specific answers.

Gordon

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post #3 of 12 (permalink) Old 06-25-2010, 03:50 PM
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I ride up to 4,300 feet in my area. The bike runs and starts ok, but there is a loss of power. Higher octane may help?

DT

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post #4 of 12 (permalink) Old 06-25-2010, 04:15 PM
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Quote:
Originally Posted by dirtrack650 View Post
I ride up to 4,300 feet in my area. The bike runs and starts ok, but there is a loss of power. Higher octane may help?

DT
Higher octane would make it worse, because higher octane gas is harder to ignite.

Use regular gas at all times. I think once you get above 7000 ft you might have some issues.

Do a google search for " Dial a Jet " ...a system that lets you increase or lower your carbs fuel to air ratio with a turn of a knob.

KM

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post #5 of 12 (permalink) Old 06-25-2010, 05:50 PM
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I ride here 7,200 ft in Mexico city and... uhmmm, how can I put it?, here the gas is really very bad... piss quality bad. Not much running issues, some hesitation going full throttle but not much more so I think you will be ok

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post #6 of 12 (permalink) Old 06-26-2010, 03:55 PM Thread Starter
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Thanks for the info All. I guess its looking good if I have to use low grade fuel....and if I have to go up high. These will be things I wont be doing often.....and wont be pushing the bike either. Just glad to know the bike can handle it if it needs to.
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post #7 of 12 (permalink) Old 06-26-2010, 04:46 PM
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The low octane and the altitude go together. Since the ambient air pressure is lower at altitude, for a given engine, the combustion chamber pressures are also lower, so pre-detonation is less likely and a lower-octane fuel can be used.
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post #8 of 12 (permalink) Old 06-26-2010, 10:44 PM
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I use 85 octane (regular) and ride at 5280 ft. (Denver) and have no problems.


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post #9 of 12 (permalink) Old 06-26-2010, 11:02 PM
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I am currently reading Jupiter's travels by Ted Simon...in that book he rides a Triumph 500 with "low compression pistons" that run much smoother than stock and work well for poor fuel encountered in his travel. Any applicability to a Vulcan 750?

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post #10 of 12 (permalink) Old 06-27-2010, 01:12 AM
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Quote:
Originally Posted by Knifemaker View Post
Higher octane would make it worse, because higher octane gas is harder to ignite.
Use regular gas at all times. I think once you get above 7000 ft you might have some issues.
Do a google search for " Dial a Jet " ...a system that lets you increase or lower your carbs fuel to air ratio with a turn of a knob.

KM
Actually, higher octane has a longer burn time. The loss of power may be compensated with 92+ octane. Same principle as piston airplane engines (108+ fuel)

DT

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'V-Twin' HWY pegs
Black 750 Spectre handlebars
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Emgo air filters
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Tail bag-FroZone Cooler
Back Rest-Igloo 6 pak cooler
WalMart Saddle Bags
R/R Relocate
Dry Splines Lubed
AGM DieHard-Sears
Gutted Goat
Sporster XL Mufflers
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Pickup coil mod to .45mm
Silverstar headlight
Rotella T6

Last edited by dirtrack650; 06-27-2010 at 01:16 AM.
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