Do I need to re-jet after exhasut mod? If so, how do I?

[Dave]

I have a shineray 200xyi dirt bike and I just did the exhaust mod to it, but I didn't put on a new exhaust cap or spark arrestor, I just took off the exhaust cap which is more like a plug. Well I noticed that when I pull on the throttle all the way it takes a while to response. Also when I'm full rev in top gear and then let go of the throttle it starts to do a couple backfires that are really loud. So i bet i need to rejet, but i dont know like what size of jets i need to go with or how i should go about this. Anyone can help? :?:

[john25]

I did an exhaust mod on the same bike, but I used a polished aluminum exhaust cap with a spark arrest screen. Check out my posted pics in another thread. I also opened up the airbox and also modified it to accept a "real" Uni Dual Stage air filter. It was way lean after the mods. It also needs a bigger pilot jet because after the mods it required 3.5 turns out to idle right. It came with a 98 main jet and a 40 pilot jet. I have installed a 102.5 main jet and have yet to find a compatible pilot jet to install. My bike has a 27mm Sheng Wey carb and neither Keihin or Mikuni have a pilot jet that will work.

Funny thing though, my 200cc ATV has the same 27mm carb with main & pilot jets that are exact copies of Keihin jets. I installed a 30mm Sheng Wey on this ATV and this carb also had exact Keihin copy jets too. Anyway, I'm going to install this take off 27mm carb on my Shineray 200 with a 102.5 main jet, and a 45 pilot jet. This should get the jetting where it needs to be.

Remember that the fuel screw should be 1-2 turns out if it's the right size. Any more than 2.5 turns out, you need the next bigger size. If you only need .5 turn out, then go one size smaller. Because my bike needs 3.5 turns out, I'm going two sizes bigger. Hope this helps.

[IronFist]

John's post was good.
If I add anything is that you could use the search feature, there is carbs ripped with pictures.
Again John was right with the jets, but if you pop yours out and take em to your local bike/atv/motorsport shop, they might have what you need or can order. At least they can identify what you have and that's gotta help your search. Or you can post a pic and someone might identify them. You'd have to pull anyway to check their size. It should be stamped on the side of the jets.