Reply To: GT250 EFI DSpec Stalls at Idle after Warm Up
That is some good insight Joe. My bike is the 250 FI version. You’re right that I have two separate pipes running from the airbox into the engine side of the carbs. However, in my setup, the two nipples coming out of the ISC stepper motor are open and not connected to anything and the pipes coming from each carb are plugged into two separate nipples on the airbox that are blocked off from factory. Is this the same on your bike? (Did someone f up on my bike in the past?)
Basically, those two ports on the engine side of the carbs are blocked off at the airbox in my setup. The carbs are also cable driven, so there is independent adjustment possible on both. Due to this, both carbs can be at different positions at a certain rpm. While the bike is idling, and you change settings on each carb, you can hear the idle go up or down, rough up or smoothen out etc. To align them by ear, I zeroed out both carbs and started from scratch (the bike wouldn’t start at this point because there is no air getting into the cylinders) and then proceeded to open them up one rotation at a time on each side until the idle sounded healthy. The bike is running well for the most part right now with the IAPs plugged in, except some random bog/sputter when I open it up too quickly.
To fine tune it from here, I am making my own manometer using clear vinyl tubing, a long flat piece of cardboard, and some suitable fluid for the liquid inside. There are a lot of DIYs out there on how to make one at home, and its quite easy. It works off of vacuum and you plug it into the port on the engine side of the carbs to check which way the liquid is getting pulled more. It gives you a good visual of what’s going on in each carb/throttle body because doing it by the ear alone is inefficient and inaccurate.
This is what a homemade manometer looks like: (https://www.irv2.com/forums/attachment.php?attachmentid=112936&d=1448751314)