Longer intake=wonky, really high jetting

[ruckmaker]

I have a PC20 carb. Love it. Since I deleted my airbox, I have a K&N breather coming directly off of it, which performance wise is great. But I hate how loud it is (yes, I'm one of those people that doesn't want my Ruck loud). So I put on a Ruck Shop intake kit on it, with that same breather on the end. And obviously that changed the jetting. But it changed it so much, I must be missing something. I went from 35m/80p with just the breather to 38m/105+ with the intake hose. What am I missing? That doesn't seem possible. I lost my 110 jet, so it may be 110 or higher. But there's no air leak, since it performs great with the 35/80 before. So help me...is that jetting way too high? And the performance suffers. I love that the acceleration is smoothed out and I love that it's quieter, but it's missing a few MPH here and there. 

Anyone have any solutions? Or is this how it goes with an intake? 

Is there a shorter intake? that would quiet the carb, but keep my performance?

Any help would be great.

[Baizy]

Did you happen to try adjusting the needle clip position prior to swapping jets?

[ruckmaker]

I didn't. You mean move it up a few notches and richen the whole thing?

[Baizy]

Oct 6, 2020 13:43:28 GMT -5 ruckmaker said:

I didn't. You mean move it up a few notches and richen the whole thing?

That's correct, my understanding is that you should always start tuning a jet at the highest clip position (leanest) and work your way to the lowest (richest) before moving up a jet size. That way you're not going up a jet size to compensate for a lean bog off of idle.

Something else to consider is that the slide carb reacts directly to throttle input as opposed the the factory NVK carbs that reacted inderectly using metered air to control the fuel through a vacuum port. My meaning behind that is that you will now have to "roll onto" the throttle, or frequently lean out, unless the PC20 has an accelerator pump built in for the full throttle rips that most rucksters are used to.

Perhaps try going back down to what worked well without the intake tube and play with the needle clip. You may find you still have to jet up a few sizes afterwards, but I am skeptical that you would have to go up 20.

Happy Tuning 😊