OK XJ genuis' - carb jetting question

[Eric_XJ]

So after a catastrophic failure of my left petcock (rubber fuel cock valve is falling apart, looks like I'll be rebuilding a petcock now) I pulled my carbs apart tonight thinking they were dirty, ect. ect. ended up being pretty clean.

When I was looking at the jet sizes, here is what I got....

180 - not sure what this jet is called, but it's the one on the back of the carb where the airbox boots are. FSM says it's a 170



130 - on what my FSM has hand written as main jet. it's normally a 112.5 according to the FSM (printed, not handwritten)



Now I have the mac 2-1's with turnouts and filter pods...my question is, is this about right for these mods ? 112.5 to 130 seems like a decent jump to me but....what do you guys think ?

[TopCatGr58]

Hey Eric,

That jet in the intake bell is your main air jet, and it's okay to be 180.

The main jet of 130 does seem a bit much from stock....jetting guide suggests about 3 sizes up for your mods....that would be 120. HOWEVER, what do your plugs look like? IF black/sooty, then you're too rich. But if they are white or light tan, then they are close to being about right. There was a MEGATHREAD posted by a previous MOD Mike Hart about a rejetting experiment he did with an XJ... search for the keyword PLUMBING...you'll find it. The XJ's YICS system is a bit more foregiving with regards to jetting sizes. YMMV!?

T.C.

[Eric_XJ]

T.C. - Thanks for the info.
I think my carbs are way out of sync then. I'm burning a tank of gas in 2 1/2 days (about 100-135 miles) then I have to flip to reserve.

[heatmanal]

Hay Eric, On my xj Im running a hooker 4into1 with supper trapp baffels,k&n pods, 125 mains, 50 pilot jets & 180 pilot air. Took it to the dyno pefect across the board on air fuel ratio. Needles set on the notch 2nd from top.82hp at the rear wheel.I was hopeing for hp but the xj does have the least hp.I need to redo my signiture.Hope this helps. Allen

[CatatonicBug]

Needles set on the notch 2nd from top.

I thought the XJ didn't have adjustable needles. Do you have a dynojet kit in yours?

[heatmanal]

just the needles

[chevy45412001]

sizes

ok. i lived in wisconsin.(i don't know if elevation changes matter) anyhoo. i was running a kerker4-1 header with no baffles. and was running 137.5 mains with whatever was in the carbs for air jet. I did however install a VERY tiny lock washer under the needle. (washer was made flat with pliers). I don't no about dynos etc. But with that set up i got the best runs at the drag strip. 13.1 at 102mph. Oh ya i also had pods. Whatever brand they were the cheapest i could find. I now live in florida and just recently went to a 132.0 main. I did buy 137.5 just because that is what i ran up north. Don't no if any of this will help but i can say 140 was way to big of a jet. Bike would bog down at speed ,so tifwiw