A55 Carb Tuning

hey guys, I recently did my first upgrade on my 2011 Tomos Sprint.

I upjetted to a 58 main and installed a Tecnigas Next-R. It runs great and gets me to about 40mph no problem. But I've noticed 3 issues since the upgrades.

First, I noticed that i sometimes have to engage the throttle to get it started, whereas I never had to do that before. Secondly, when im idle somewhere and want to accelerate, I have to hold the throttle for a bit before it finally moves the moped. Also I can't just go into WOT when i want to I have to sort of build it up from a stationary position as opposed to when it was stock. Is this normal? I'm a complete noob at all this stuff.

Lastly, and my biggest worry is this noise coming from the air filter. I don't know if its the new air filter + exhaust or what, but I've included a video where you can hear the noise. Its like a higher pitched sputtering you can hear over the engine itself. Just wondering is this normal?

Heres a video:

Thanks for any help in advance everyone.

Re: A55 Carb Tuning


Re: A55 Carb Tuning

have you done any plug chops? i had similar results after adding just a hi flow filter and upjetting to 58, i had trouble starting & bogging at mid - full throttle. went back to stock and everything was fine. try ditching the filter and running the stock air box and see if that helps, you may need to upjet more regardless of filter or not.

and the sound from the filter sounds normal.

Re: A55 Carb Tuning

As otherwise stated your engine "IS" Lean. I did not see where you made any adjustments to the Needle or Idle Air Screw. I "Had" exactly the same set up but needed a 65 Main Jet AND ended up with the needle in the 5th from the top Position. Also depending on the Temp the Airscrew was between 2.5 turns out to 4.5 turns out

They are "Very Sensitive to the Outside Air Temp & Humidity" In Washington, DC the temp range in the last 30 days has been between 65 to 105 degrees. That is a 40 degree spread.

A "Plug Chop" is very hard to do well with an Automatic trans. You must ride in in the throttle position you are having the problem with for at least 1/4 mile and then quickly while turning off the engine stop the Bike a FAST as Possible to keep the extra fuel from changing the plug color.

It also helps to have a Light and Magnifying glass to see the Bottom of the plug where the Porcelin touched the Steel shell. If it is WHITE there it IS lean. You also want to see a little Oil on the threads.

Last, you may want to put the bike on the centerstand and rev it a little and right where it is struggling lift the shoke lever a little. If it picks up speed then for sure you are also lean! Only do these test when the bike is up to operating temp. If the lean spot is part throttle you will most likely need a larger Main and possibly raise the needle. They really like the 4th from the top position. (edited)

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