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What octane fuel is considered the best I was running 91 non ethenol read that it was designed for 87 so began to use 87 non ethenol but find at lower rpm’s it wants to knock
 

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87 is best, but it may have carbon buildup that's leading to the knock. Seafoam in the gas can help clean it up.

Higher octane will promote carbon buildup.
 

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Are you getting knocking when under load at the low rpm and can't downshift into a lower gear? This time of year you can easily get "bad gas" that may have condensation/water in it. Oddly enough to combat water in the gas another alcohol additive like HEET is sometimes used (methanol).

You might try getting you gas at a different station. My son used to put premium in his bike until I convinced him it wasn't necessary or recommended by Kawasaki. These engines were designed for 87 octane.

I routinely add Seafoam to my tank every three or four time as it helps keep it running better. Check your spark plugs (condition, age and correct heat range) and consider checking/modifying the pickup coil gap. The compression on these engines is not high enough to require premium fuel and around here in California I don't think I can buy gas without ethanol in it, at least 10%. My bike doesn't knock (knock on wood). Knocking on a motor like the 750 with 4 valves per cylinder is usually related to carbon build up, weak spark, timing or in my experience bad gas. (Although perhaps a lean condition caused by a dirty or gummed up carb may add to the problem.) Seafoam and Techron additives may be your friend, I swear by them especially this time of year.

I had never heard that higher octane gas could cause carbon buildup. I will need to look into that as I am always learning new things. (Or forgetting things I once knew, I don't remember which.)
 

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Since higher octane burns slower and cooler, it will create carbon in our engines, or any engine not designed for it. Along with slower starts, reduced power, and lower mpg.
 

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2001 Kawasaki Vulcan 750
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Are you getting knocking when under load at the low rpm and can't downshift into a lower gear? This time of year you can easily get "bad gas" that may have condensation/water in it. Oddly enough to combat water in the gas another alcohol additive like HEET is sometimes used (methanol).

You might try getting you gas at a different station. My son used to put premium in his bike until I convinced him it wasn't necessary or recommended by Kawasaki. These engines were designed for 87 octane.

I routinely add Seafoam to my tank every three or four time as it helps keep it running better. Check your spark plugs (condition, age and correct heat range) and consider checking/modifying the pickup coil gap. The compression on these engines is not high enough to require premium fuel and around here in California I don't think I can buy gas without ethanol in it, at least 10%. My bike doesn't knock (knock on wood). Knocking on a motor like the 750 with 4 valves per cylinder is usually related to carbon build up, weak spark, timing or in my experience bad gas. (Although perhaps a lean condition caused by a dirty or gummed up carb may add to the problem.) Seafoam and Techron additives may be your friend, I swear by them especially this time of year.

I had never heard that higher octane gas could cause carbon buildup. I will need to look into that as I am always learning new things. (Or forgetting things I once knew, I don't remember which.)
Disclaimer: Don't believe what anyone including me says unless you have documented engineering proof.

The User Manual does indeed recommend 87 octane or higher.

According to AMSOil, octane has nothing to do with energy content or quality – it’s a measurement of the gasoline’s ability to resist engine knock. Higher octane denotes greater knock control.

Higher octane fuels are recommended for engines with a higher compression ratio. Increased compression allows an engine to extract more mechanical energy from a given air/fuel mixture but requires higher octane fuel to avoid knocking caused by pre-detonating.

The Vulcan compression ratio 10.3 to 1 is rated as "medium compression" and is high enough to use 91 octane gas. A fact of physics.

Knocking can also be caused by carbon building on the piston crowns. Deposits can reduce cylinder volume at top dead center, effectively increasing the compression ratio. This alone can lead to engine knock.

Remember that higher octane does not mean more/better additives.

The composition and effectiveness of additives is highly complex and often debated by word-of-mouth or "it feels better", but should be kept real based on facts of physics and engineering.

Techron from Chevron/Texaco/CalTex and V-Power Nitro+ from Shell have engineer-proven additives that help reduce carbon and keep fuel components clean.
Techron ingredients:
Distillates, hydrotreated light at 40-70% weight
Stoddard solvent at 15-40% weight
Solvent naphtha (petroleum), light aromatic at 5-10% weight
1,2,4-trimethylbenzene at 1-5% weight
PEA (detergent), polyether amines at 20-49% weight


Red Line SI-1 Fuel Additive has similar but stronger racing and engineering recommend ingredients:
30 - 50% PolyEther Amine
1 - 10% IsoOctanol
5 - 20% Aliphatic Naphtha


What's in the other 20% it doesn't say...

Seafoam ingredients from their OSHA datasheet:
Hydrocarbon blend < 95%
IsoPropanol < 25%
Note:The exact composition of the above listed chemicals are being withheld as a trade secret.


Seafoam has a huge word-of-mouth following and people swear by it but it is a mystery so I stick with the alternatives that are race and engineer-proven.
 

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Until I joined this forum I had never even heard of Seafoam. Coming from Colorado to California I actually thought it was some kind of coastal voodoo juice brewed in guys garages. It was some time even after reading about various carb cleaning methods and other fuel related "miracles" I happened to see it on a shelf at my local NAPA here in CA close to the Techron bottles. Since having came to California and dealing with regular smog certifications I began using Techron after it was suggested by a friend who, at the time was a smog tech. I found that Techron did indeed help with the dreaded CEL at smog time in the Ford Thunderbird I had at the time. I still use Techron additive in my daily driver cage, adding a bottle every 1,000 -1,500 miles and add Seafoam if the fuel trims get wonky.

Since Techron worked, I grabbed a bottle of Seafoam for my Vulcan. I found that using some of it when I filled up every month or so actually improved my starting and idle. Since my son and I both ride Vulcans and had about the same mileage and we also got fuel at the same station it was easy to compare results. Consequently I will use it since it works for me but I am not going to go out and try to become a local distributor. Other's results may vary.
 
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That is good info and once I get my beast restored and running that can be something to check out. I had same initial reaction WTF is Seafoam?
 

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Right around 1000 to 1300
That's really low rpm to be pulling, idle speed. It would probabaly knock under the best conditions at that speed.
 

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Since higher octane burns slower and cooler, it will create carbon in our engines, or any engine not designed for it. Along with slower starts, reduced power, and lower mpg.
Well I've been doing it all wrong. I started using mid grade gas a few days ago and noticed it has ran better I thought it was in my head though. Thank you for the information on this.
 
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