First time I have ever posted so forgive me if someone has asked this. I just installed a Big Gun rear on my 01 raptor. Results.....killer sound, simply can't be compared to stock. This thing sounds so wicked it makes it all worth while, however my tach says I am only getting about 8000 rpm. It simply does not feel like it is pulling. My buddy on his YZ 426 blows by me like I am standing still and another on a KTM 200 is almost keeping up!! And I am speed shifting. Should I be jetting and if so which ones? Does anyone know or have a phone number for Big Gun?

Thanks

 

A big gun rear? What I am asuming you mean a silencer. I talked to them they said the silencer should give you 4hp more if its the full exhaust 8-9hp. I'd say you should jet it and try a different air box set up. Pro Design has a airbox eliminator kit for it go under *********.com or atvscene.com I saw it under one of those sights. Big gun has a web sight biggunexhaust.com you can get there # there.

 

*********.com for above post

 

For some reason it wont let me give out the sight let me try it this way atv s ou r c e . com

 

sounds like it may need to jet up the main a size.

 

Bingo1,

The Yamaha head pipe sucks, they screwed up where the two goes into one so you won’t get a big hp gain until you change that pipe. This is why a lot of the slip-on’s don’t require rejetting. For now you can try raising the needle (move the clip down one), going up one on the pilot (22.5 to 25.0) and going up one on the mains (140/145 to 142.5/147.5) and removing the snorkel. If you get the Pro-flow air filter and run without the airbox lid you could go up another size on the main jets to 145/150. This is all at sealevel.

Good luck, getting to those carbs it is a real pain in the ***.

 

Big Gun told me to increase the main jets by 2 sizes for the silencer. Mine was stock 140 and 145 (right side is 2 sizes larger to compensate for the 3rd intake valve). Just move the main jet from the right carb to the left and get a 150 main for the right. You'll need the small round style and make sure it has a tapered seat. The flat seat jets will not work. You almost need a magnifying glass to see the difference. Also, don't try to separate the carbs. They come loose as an assembly after removing the boots to the airbox. Let me know how it runs after doing this. I set mine up, but haven't ridden it with the changes yet.

 

Thanks for the input to all. I finally spoke with Paul at Big Gun. He advised to go from the 140 to a 150 and from the 145 to a 155. Also to move the pilots to 27.5 (it seems they are 22.5). Now all I have to do is find the jets. Can you believe my dealer has no idea where to get them as of now!?!? I'll update all after I do the changes.

 

It will be hard to beat a yz426 no matter what you got!

The stock headpipes look too narrow, restricting flow and reducing HP. CT Racing has a full exhaust at nearly 50HP with K&N filter and jetting.

 

Bingo, the changes that Paul suggested are for use with their full exhaust system. If you only got the slip-on, you need to see my previous post and only go up 2 on the mains.