Help jetting a PD18J carb

[ruckmaker]

Got a PD18J carb for my '19 Ruckus. Installed easily, little wiring for the auto-choke. Now I'm confused about jetting. On my stock carb, with my airbox delete and OEM exhaust (after market is too loud for me), I was running a 38/78 with no shim. Worked great. Maybe could get a little better, but it's close. 

Put in the PD18J, which is bigger, so I assumed bigger jets. The main I'm using so far is big. Using a 100 (no air leaks, it actually likes the 100), but the pilot jet I have is a 33 which cam in the carb. Shouldn't it use a bigger pilot than stock? I haven't screwed with the pilot much, since the 33 is running fine and i'm still calibrating the main (went from 78 all the way to 115, now back down). 

Anyone else have an example of their jetting in a PD18J carb or any high flow CV carb? I feel like I'm missing something. Only squeezed out a little more top speed and a little acceleration. 

I'm 6'3, 230 (literally losing weight as we speak to make my Ruck faster) and live in New England at sea level. 

Any help would be amazing. New here, so I probably broke some rule with this or something. 

[Baizy]

With a higher flow carb your air will be travelling at a lower velocity and creating less vacuum through the carb. Lower vacuum will make it harder for the vacuum slide to travel upwards and open the pilot jet completely (IE give full fuel). I'd try a 33/80 combo, take it for a 20 minute rip and then check the plug. Get the idle setup right as it's going to affect your whole top end range (slightly, but enough to matter) then patiently go through different main jets. Give each jet a real chance with 20 minute rides (unless it dies off idle) and you'll find the right one with time.

[ruckmaker]

Landed on a 33/105. Doesn’t make sense to me, but neither do carbs. Got my Ruckus to a hair under 42. Outside Boston, so not many flat roads, so I’m consistently hitting 38-39, but don’t have the space to find out how much higher. And this is without tucking. I think tucking is dumb, since it’s a commuter bike and I’m not gonna be tucking like a tool on the way to work.

About to switch to a PC20 (I got both, because I realized there was no auto choke on the PD18j) and hoping that squeezes a little more power out. Not happy with not having an auto choke, but we’ll see.

Also, realized reading plugs is a lot harder than just trial and error and recording speeds and RPMs.

[Baizy]

Sept 19, 2020 6:13:14 GMT -5 ruckmaker said:

Landed on a 33/105. Doesn’t make sense to me, but neither do carbs. Got my Ruckus to a hair under 42. Outside Boston, so not many flat roads, so I’m consistently hitting 38-39, but don’t have the space to find out how much higher. And this is without tucking. I think tucking is dumb, since it’s a commuter bike and I’m not gonna be tucking like a tool on the way to work.

About to switch to a PC20 (I got both, because I realized there was no auto choke on the PD18j) and hoping that squeezes a little more power out. Not happy with not having an auto choke, but we’ll see.

Also, realized reading plugs is a lot harder than just trial and error and recording speeds and RPMs.

Hey glad you settled on a jetting setting that works for you. I came across some interesting info from my reading (and parts bin) that makes an 18mm carb less impressive on newer rucks (2015+).

In 2015 Honda went from a 15mm NVK CV carb to an 18mm NVK CV carb but kept the same jetting as the 15mm. 35/75 for lower elevation applications. I am looking forward to doing a direct comparison of of performance between stock parts between different model year and writing up posts describing the differences felt between the two.