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I have a 2005 Burgman 650 with 484 miles on it. When I am cruising at any speed and let off the throttle I hear a popping out of the exhaust or some people would call it back firing. I filled up the last time at Shell and put in 91 octane v-power and I was wondering if this was the cause or not? Before I used 89 octane at Casey's and didn't notice it doing that but I can't be for sure. I took it by the dealer and he said he hasn't seen any of these problems before and told me the next time I fill up put in 87 octane. Does anyone have any good solutions???
Thanks
 

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Okay, I can't help with your problem, but I have to ask how putting higher octane fuel in the bike can cause this?
 

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Wait untill the 600 mile service, tell the dealer about any problems you may be having. The 600 service is THE most important service that is done. It's more than an oil change, it's a good going over of cables, linkages, Bolts tightness check, etc. When I took my 400 in it was doing that same thing at about the same mileage. I told the dealer about it. He made an adjustment to the carb, (it wasn't closing enough) and it never did that again. My 650 hasn't done that yet, but it may be, just a simple adjustment is all that's required.
 

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I have listed several times that whenever I put higher than 87 octane, my 650 back fires too. Runs fine with 87 octane though.

Kelly
 

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mrlansi said:
I took it by the dealer and he said he hasn't seen any of these problems before and told me the next time I fill up put in 87 octane. Does anyone have any good solutions???
Thanks
dealer said:
the next time I fill up put in 87 octane.
The dealer knows your 650 was designed to run on 87 octane gas, so that's why he suggested you go back to it. 89 octane was probably still within the engine's tolerances, but 91 octane is too high a level for it.

The octane rating, as I understand it, is basically a measure of how much the gas can be compressed without self-igniting. High-octane gas is intended for cars with high compression engines, and may not be completely burned in lower compression engines. The remaining gas goes out the exhaust pipe, where back compression from braking when you get off the throttle might ignite it, causing "backfire".

My advice? Put the gas in the scooter that the manufacturer recommends.
 

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Jim said:
When I took my 400 in it was doing that same thing at about the same mileage. I told the dealer about it. He made an adjustment to the carb, (it wasn't closing enough) and it never did that again.
That adjustment would be next to impossible on the new models - they have shrunk the carb down to the size of a fuel injector...
 

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I started running 89 octane for the past several fill-ups and mine started doing a little popping on deceleration also (over 14,000 miles on mine). It seldom does that using 87 octane regular. It's the gas. It's also not a big problem. A real backfire is more violent - this is just a bit of unburnt fuel mixture igniting in the exhaust. The only reason that I am running 89 octane is that it is cheaper than regular where I live. State law prohibits them from charging as much for the 10% ethanol content in the 89 octane fuel as they charge for "real" gasoline. If regular 87 octane was cheaper, I'd be running it. The 650 does not need any higher octane.
 

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This is good info to know. Now I hope I can remember to push the button on the left instead of on the right! I have been using 93 octane for the truck since day 1, with 1 mistaken exception. And it was a huge mistake!

The Beast absolutely HATES 87 octane, to the point that I had to drain 25 gallons of gas out of the truck and into my son's little Nissan, gas cans, milk jugs, water bottles, etc. You get the idea.

When Ford says "use only 91 octane or higher" they mean iit!
 

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Here,in Spain,the lowest octane gas is 95.All the 650 owners I know,use this type without any problem.
 

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Alan_Hepburn said:
Jim said:
When I took my 400 in it was doing that same thing at about the same mileage. I told the dealer about it. He made an adjustment to the carb, (it wasn't closing enough) and it never did that again.
That adjustment would be next to impossible on the new models - they have shrunk the carb down to the size of a fuel injector...
I had a 2003, it still has a throttle plate (for the air) with fuel injection.
 

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My Comments

First I don't believe that the octane you use has anything to do with the slight backfiring. For the additional additives in it I only use 93 octane and do not have this. Your backfiring, and that is not exactly what it is, is probally caused simply by air entering the exhaust system. You have a PAIR System installed that does exactly that though unlike many other bikes I have owned the B-650, mine at least, does not do the backfiring frequently normal with the PAIR System. I would have your dealer inspect your exhaust system and the PAIR System. On many of my past cruisers, sport and race bikes I have removed the PAIR System, made and installed block-off plates which prevented what you describe.
 

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xirris said:
Here, in Spain, the lowest octane gas is 95. All the 650 owners I know, use this type without any problem.
pauljo said:
I may be wrong, but I believe your octane rating system is different from that used in the USA. I'm sure someone on the forum knows for sure.
Paul is correct.

In North America we rate octane level using the R+M/2 method. In Europe you use the Research Method.

Suzuki recommends 87 or higher here, which is the same as 91 or higher there.

4DThinker said:
The octane rating, as I understand it, is basically a measure of how much the gas can be compressed without self-igniting. High-octane gas is intended for cars with high compression engines, and may not be completely burned in lower compression engines. The remaining gas goes out the exhaust pipe, where back compression from braking when you get off the throttle might ignite it, causing "backfire".
That's essentially correct, although the Burgmans are high compression (they just use advanced fuel injection timing techniques to overcome problems related to low octane fuel).

Gasoline is a mixture of several hydrocarbons: hexane, septane, octane, heptane, etc. The longer the hydrocarbon chain, the harder it is to break apart, so more heat is required to ignite it.

Pure hexane is so easy to ignite that the heat of compression can ignite it before the piston has reached the top of its stroke, causing "pinging" or knocking. Adding octane to the hexane reduces this problem. Adding chains smaller or longer than octane will raise the flashpoint accordingly, and the octane rating is a way of indicating the mixture.

On the opposite side of the scale from preignition; if too high an octane fuel is used it may not burn completely during the power stroke, and unburned fuel can get into the exhaust system where hot gasses from the next stroke can ignite it. A small popping sound is usually the only symptom, but it can negatively affect fuel mileage and add to air pollution. Adding air to the exhaust as part of an emmission control system can allow the excess fuel to burn more completely, but may increase this popping sound.

Wyldman said:
...The Beast absolutely HATES 87 octane, to the point that I had to drain 25 gallons of gas out of the truck and into my son's little Nissan, gas cans, milk jugs, water bottles, etc. You get the idea.

When Ford says "use only 91 octane or higher" they mean iit!
With the possible exception of California, in most states you can buy "Octane Booster" products that you pour into your tank to mix with the existing fuel if it's too low an octane to work properly. Beats having to drain 25 gallons.

HTH.
 

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My Moonpie "spits" every once an again. 'specially when decellerating and re-acellerating. it doesn't effect my operability tho. (but - it does sound [sorta] like a "pop.")

after it does "that" - it is ready for my command.

it is rare - only happens once a week - on a weird "off twist go around a corner thing."

pete
 

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Pete said:
My Moonpie "spits" every once an again. 'specially when decellerating and re-acellerating...it is rare...on a weird "off twist go around a corner thing."
Mine does that, too, but very rarely. More often when banking into a right turn than a left if I recall.

Unless it starts doing it often I won't worry.
 

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Mine backfired for the first time yesterday and it did it several times. I wonder why it made it to nearly 3000 miles before it started backfiring.

Brian, thanks for your informed and easy to understand explanation of what octane does. I have read article upon article and post upon post that went to great lengths to try to tell the octane story and didn't tell it as well as you did. Just out of curiosity where did you get your info?
 

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Paul Barnard said:
...Brian, thanks for your informed and easy to understand explanation of what octane does. ...Just out of curiosity where did you get your info?
Years and years of study. :wink:

Seriously, several places. High school and college chemistry, reading Road & Track, pilot's ground school, etc. I can't point to a single source.
 

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I switched to running 89 octane several tankfuls ago. Why? It is now 10 cents a gallon cheaper than 87 octane in Nebraska (due to the 10% ethanol content). I am not getting an excessive amount of backfiring or popping though. The scoot has always popped a little bit on decelleration every now & then, but it doesn't bother me, and it is sporadic (not all the time).
 

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I've noticed a little pop now and then when decelerating.
Hardly noticeable.
 
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