Just wondering what size jets are ont the raptor now i have the fmf power core on there and it runs good but I have been told that with a new pipe you should re jet it. I am gonna try just going with one size higher on each side...is that a good idea is anyone else running the fmf at sea level.

 

One size??? Try 10! These things run really lean! You'll be an expert at taking the carbs apart before you're done, the way your going.

 

Hi Bigkdwag,

If your ATV is running good check your plug before you do anything. If the color is right, light tan, you're ok. If it's white or light gray you are too lean and if it's black you're too rich. You didn't mention what altitude you're riding at or whether your dealer rejetted your machine for the correct altitude. I live in Denver and I try to jet for 4000 - 6000 feet, I'm running 130/135. The stock jets for the Raptor are 140/145, that's for sea level.

I spent an entire weekend trying to get an open air box to work because I used the jet sizes the manufacturer, CT Racing, suggested. When I finally got it running right again I had the jets back to where I started. Like you, I always heard that you need to rejet when you change anything to do with the exhaust or air intake. It would be more correct to say that you need to make sure you are not running lean after making any of those changes. Automatically assuming that you need to increase your jet sizes can be a mistake.

When I changed the air box, CT racing suggested going up two sizes and asked what I was currently running. I told them 130/135 and they immediately suggested that I go to 150/155 to start. Had I stopped to think I would have realized that two jet sizes would have only been +5 not +20 as they suggested. From what I've heard you sould only have to go up one size for a pipe, which would be 2.5. For an air box and pipe you would probaly need to go up +2 or +3 sizes **IF** your machine is already jetted correctly. Check the plug first, you may save yourself a lot of time. In my case the Dealer had rejetted my machine for Denver's altitude but it was still too rich. Adding the air box just leaned it out enough.


Good luck,

 

I have a stock Raptor with the FMF Powercore IV and i live in Johannesburg @ 1400 odd meters. According to the installation "manual" from FMF nothing needs to be done to the jetting. If you drill holes in your airbox lid or remmove the airbox lid you will need to re-jet. After chatting to Yamaha I understand that the Raptor comes jetted a bit rich from the factory so fitting an after market Headder or removing the spark arrestor shouldn'tpose any problems.

 

Well I am at sea level. and when I come off a jump and go just maybe ten feet or so into a corner it will stall. I also had the boots come off for the first time ever. So i am thinking it needs to be jetted........

 

RaptorFMF, I am thinking of getting the FMF slip-on or the full. Do you like yours and can you feel the power change? And what else if any you have done, like air box mods, etc. And you said you didn't rejet, were are you located? Thanks

 

I love mine you can definetly tell the difference it is hard to keep the front end down and that is all i have done engine wise......

 

The FMF is great[img]i/expressions/face-icon-small-happy.gif[/img]. A mate of mine has the Pro Circuit which in my opinion sounds better but the FMF pulls stronger. Before I fitted the pipe I could only climb about 2/3 as high as I climb on the dunes now! I am very happy with it and it sound much better and is much lighter than the stocker. I would guess I have about a 10-20% power increase depending where you are in the revs.

 

I have not done any other mods (airbox etc) but i am thinking about drilling holes into the airbox. After emailing FMFracing they said a re-jet may be needed so I will wait until my bike is back from a service and decide then. In South Africa things like jets for a Raptor can be difficult to find.

 

Thanks alot for the responses. I think I will try the FMF out. I also heard it was quieter than Pro-Circuit and Big Gun. And those two are the othres I was thinking of. Thanks again[img]i/expressions/face-icon-small-cool.gif[/img]