Using the hot start lever/button often?

I just want to share with you a problem I had on a 2007 Honda CRF250, where it was very difficult to start when COLD and HOT. This 4 stroke would COLD start with choke on and run for about 10 seconds before it would die. Restart with choke on or off was very difficult. The only way it would restart is with the hot start lever pulled in? Why?

What is a hot start? And when do I use it?

The hot start simply adds more air to the fuel/air mix needed to start a HOT or STALLED engine.

The Fix?

Before I reveal what the easy fix is, let’s talk a bit about why this is occurring. Using the hot start leans the mix out, and considering this is needed on a COLD engine, it clearly tells me that the bike is running rich. So how do we lean it out? By adjusting the fuel/air screw. I turned the fuel/air screw in 1/2 a turn, and the problem went away! Turning this screw in clockwise will lean the idle mix, while counterclockwise will richen the idle mix.

The proper way to tune a fuel/air screw is to make adjustments on a fully warmed up engine and at LOW RPM. Lightly seat the fuel/air screw and set to factory settings as a baseline. With engine running at low RPM, turn the screw in clockwise until the engine begins to stumble, then turn the screw counterclockwise until the engine stumbles, noting how many turns in/out both occurred. Now, adjust between these two settings to achieve highest RPM and smoothest running engine. Reset idle to recommended settings and test ride dirt bike.

UPDATE: Check out this video on fuel screw tuning.

Feel free to leave comments below if this has helped you with hot start issues.