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Discussion Starter · #1 ·
Hello all, I recently purchased a 02 Raptor 660. The previous owner did not take care of this machine and it has not been riden in a year. Since I bought it I have been putting money into it every week.

Right now it is running pretty decent except for a few things. When I pull the plug it looks like black carbon on the end. When down shifting the raptor backfires a good bit and the last thing is when I pulled the lid of the air flow box there was some fuel laying in the air box.

This forum is great and I have been reading it when I would get stuck with something.

I would really appreciate some feedback on this from some of you veterens. Thanks in advance guys!
 

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i would start with cleaning the carbs really good,use speaker wire to run through the passages on the jets. Welcome to the forum!!!Lots of knowledge here...
 

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Discussion Starter · #3 ·
Yeah thanks Stud! This is a very useful tool.

Also I forgot to mention that I am certain that it is all bone stock.
 

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also you can download the service manual to if you need detailed info to...there is a sticky on this.When cleaning your carbs make note of what size jets are in the machine and your elevation and report back.
 

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what fuel do you run in it? it calls for 91 pump gas for a minimum, if regular has been ran in from the previous owner this can cuase your bike to run alittle off...it was the same with my 05 i just got in may...the spark plug was really carbon covered when i pulled it out and it was backfiring too so i changed my spark plug and have ran only 91 in it and it has helped alot my plug is not carboned at all but is a beige color which mean its running normal..try it and see if it makes a difference if not then you may have to tune your carb a little because maybe your getting too much fuel which causes backfiring or you may have a leak in your exhaust that's causing the backfiring as well. when the exhaust sucks air in it causes the backfire...
 

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Make sure there are no intake leaks. i.e. the intake boots/head. Thats a common place.
 

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it calls for 91 pump gas for a minimum, ...
Sorry, but this is NOT correct (unless you're in Europe). Manual calls for Regular Unleaded 86 Octane ([R+M]/2) - the standard US designation.

This is the equivalent of 91 RESEARCH OCTANE (the designation used in Europe and elsewhere).


Popping on deceleration is due to being too lean in the pilot (idle) circuit - you pilot jets are probably partially plugged due to sitting too long with fuel evaporating from the float bowls... time to remove and clean the carbs - thoroughly!
 

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I am unique
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Sorry, but this is NOT correct (unless you're in Europe). Manual calls for Regular Unleaded 86 Octane ([R+M]/2) - the standard US designation.

This is the equivalent of 91 is RESEARCH OCTANE (that used in Europe and elsewhere).


Popping on deceleration is due to being too lean in the pilot (idle) circuit - you pilot jets are probably partially plugged due to sitting too long with fuel evaporating from the float bowls... time to remove and clean the carbs - thoroughly!
I agree...............
 

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My 2004 manual says "Your Yamaha engine has been designed to use regular unleaded gasoline with a pump octane number ([R+M]/2) of 86 or higher, or research octane number of 91 or higher." just like Quad said but I always run premium in mine anyways (Probably just wasting my money though...LOL)
 

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Master of the Electron
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The US uses The R+M method so here your raptor requires 86 octane... if you're in europe, they use the research method so there you would use 91 - THEY ARE THE SAME octane, just a different unit being used (like inches vs centimeters)...

So, to repeat for the LAST time - if you are in the US, a stock compression 660 requires no more than 86 octane fuel (regular pump unleaded). OKAY?
 
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