racing carb jet size

[jwr3k]

So, I want to dial in the jet on my 'racing carb', the style in the photo below. What size range should I shoot for when picking out a set of jets? What is the size of the stock jet? I was looking at a set that goes from 60 to 80 in increments of 5. This seems like a bit of a jump between jets. What size range would you guys recomend starting with?

Thanks

 

[HumanPerson]

RunTong carb.
Depending on the altitude you live at, the jets are the only change to make.

I live around 1300ft above sea level and use a #69 jet in a modded carb(that same carb) with a ported cylinder.

Good carb in my opinion for starters. Where are you at in the world? Do you like grape jam?

60-80 will do. Stock jet is usually #70 but I have recieved that same carb with a #68 so you're on the right path my friend!

 

[jwr3k]

my elevation is 197 ft (60 m)

ok yeah, know that I know the stock size I at least know where to start. I do believe I need to go to a slightly smaller jet size. perhaps I'll start with a 60-70 set. Im assuming smaller number equates to a smaller jet size

 

[HumanPerson]

What problems are you encountering at this time?

On a stock engine, if i remember correctly, i used the #66 jet.

Yep lower # = smaller hole in the jet.
Ya have any pictures of your ride?

 

[jwr3k]

it runs fine for the most part, but it's running a bit rich even after getting the mixture screw dialed in. Something interesting to note, when I ran out of gas, the bike accelerated significantly for like 15 sec before cutting out. so, that also makes me think it might go a little faster and turn my spark plug less black haha

 

[HumanPerson]

Yeah, jet down

Nice bike

 

[jwr3k]

Thanks I love it, and right now it's my only transportation too. I live about 12miles one way from town so I definetly get alot of use and joy out of this thing.

I think maybe I will try a #65

 

[HumanPerson]

Ride Safe and don't stop for any zombies

 

[Chainlube]

it runs fine for the most part, but it's running a bit rich even after getting the mixture screw dialed in. Something interesting to note, when I ran out of gas, the bike accelerated significantly for like 15 sec before cutting out. so, that also makes me think it might go a little faster and turn my spark plug less black haha

When you run out of fuel like that, it causes the engine to run very lean so gets faster. You don't want to run it like that for very long, unless you want to make a piston bowl bong.

 

[Jug]

I run a 105 jet in a 21mm drilled oko
I have a g2 reed with it and a fully ported cylinder. The 105 runs great and if i go leaner it bogs out, i mean i would go for richer and bore your intake a little. You will feel the difference.