Bonneville America Forums Forums Technical Forums General Tech Octane--- 05 America

I know manual says run 89 octane. I have run all 3 grades in mine. It performs much better with 87. I know 87 gives better performance in a low compresson engine. All the metric bikes recommend 87. Why does triumph recommend 89?..... My buddie has a 06 750 shadow with 9.7 compresson as ours is 9.2 and his manual says run 87. One more question, Were are our air/fuel adjustment screws on the 05 Anerica? Thanks in advance for any and all help.

The formulation for gas varies from on refiner to another and also by area. For that matter, it varies by season. Because of this, Triumph plays it safe and specifies middle grade. Another consideration, eventually carbon buildup will raise the compression ratio, and you will need higher octane.

Could have something to do with the way heat in a parallel twin engine is retained or dissipated. If 87 works and you have no pinging, use it. Others on the board have also had good results with 87 octane. I use the 89 because it's recommended and the heat in summer around here doesn’t encourage cooler running engines.

Look in the tech vault for carb info. Lots there including pictures and links.

The pilot screw (Air adjustment screw) is located at the frontmost part of the carb, you may need to either remove a little al-u-minnie-um cap or use a D-Tool if it is not slotted. Most of the newer bikes require the D-Tool.
Here is a picture, it is the top most one, notice the carbs are laying with the rearmost part down.


And I run 89 octane in mine, big bore though with 10.5:1 compression. It likes it just fine.

I got my '03 TBS w/o an owner's manual (Haynes on order), so
I've been running 93. It's nice to know I can save some money, since I've been getting low 30's for mileage.

I have a stock 06 TBA and run 93 I have failed to get less than 38 mpg yet.

I live in NW CT and do alot of shifting due to the hills and it still gets great gas milage.

I usually run 93. Will have to try the 89. I get 42 mpg consistantly

I've been running 93 octane since day 1 on my 05 TBA and I'm getting 160 miles before hitting the reserve. So I think I'll stick with what I've been doing even though I'm not sure if it has anything to do with it. I think its really because of my 19 tooth front sprocket

Octane only applies to the ability of the fuel to resists premature detonation due to compression and heat. As long as the fuel does not cause your engine to ping (premature detonation) you’re OK. Specific gravity of fuel can make a difference to milage. For instance JP5 is the standard Navy jet fuel. It weighs a bit more than other jet fuel and has more BTU’s available per gallon. Because of that an aircraft burning JP5 can go a bit farther than one using standard commercial fuel. Similarly, here in Iowa everyone seems to love ethanol blended gas. But because ethanol has fewer BTU’s per gallon than gas, fuel mileage is lower. Pure gas may have a lower octane but it will get more miles per gallon.

My '06 TBA (bone stock) is one month old today. I've run 93 in it since the first fill up (just clicked over 1000 miles on it today). I've never hit the reserve before 155 miles. My best tank was 162 before reserve. I do have to disclose that I've been VERY gentle during my self imposed extended break in period. I've never run it up fast and I've not gone over 60 mph. However, with gas prices going up the way they are... I may try 87 and 89 and see what happens with the MPG.

raylloyd, Dealer recommended 89 oct, said 93 would run too hot, I have consistently obtained 46-50 mpg. 46 mpg when I was really letting getting on her shifting around 6000 rpm. I have often thought of running 87 oct but I know 89 burns cleaner. One area not mentioned is the brand of gas, Suncoc, Mobile seemed to work well, Getty was not good or was it he station. I’ve never tried Shell ( in NW CT $.05-.10 more per gall) and no way will I use Cumberland gas even if its listed as Gulf.

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said 93 would run too hot,

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That's nonsense. The octane rating of fuel has nothing to do with how hot it burns. It is only a rating for resistance to ignition. That's it. Period. The higher the number, the greater the resistance to ignition. Higher octane fuel is needed when running high compression engines and/or advanced timing. If anything, using too high an octane fuel will cause your engine to run too cool resulting in plug fouling and carbon buildup. 89 is the recommended rating, and I'm sure that Triumph has done the research necessary to determine the proper fuel for the bikes.

In Aus it sounds like we have different ratings for fuels, probably due to the metric / imperial difference. Standard unleaded is normally 89octane, premium is 95octane, and most stations now have a super premium (BP ultimate, Mobile Synergy, Ampol vortex, Shell optimax) that is 98octane!!! BP & Mobile have had best reports, Ampol is good, and the Shell has had bad reports from most shops.

I run mine on BP ultimate 98oct which has had best results for my bike. It has some additive that look after your engine while providing better octane rating. So in theory you don't have to run your engine as hard to get same performance which equals better miles per litre (although I usually run it full twist anyway!).

Right you are. Just a different system.