Engine Trouble Hard cold starts


Local time
10:18 PM
May 19, 2023
Hey all! So now that i got my Jackshaft kit kinda installed onto my bike i need to kickstart it via the pedals. The bike with the jackshaft is really hard to cold start but my other bike starts fine even if i kick start like this: Turn on fuel and choke to ON position, lift rear wheel and kick the bike over (it starts on first kick), pull in clutch and move choke to about half way and let it run for about 30 seconds and then turn the choke to the OFF position. I do all of this without it stalling once...
The jackshaft bike however needs about half throttle for it to start and needs alot of playing around with the choke until it warms up.
Both bikes are stock except the Jackshaft one has a home-made exhaust from a pocket bike.
-Carb is clean and adjusted right (maybe a bit on the lean side, adjusting needle clip doesnt help)
-Spark plug and gap is good (same as the one that starts with no issues)
-Spark color is also good (blue/purple-ish)
-No air leaks (i think at least since the idle is good)
Sounds rich to me. Opening the throttle and it starts= more air and less fuel. It's the same thing with old carb cars and hard-hot starts. The fuel in the bowls heat soaks, expands or boils, drains down the intake and basically floods the engine. Takes a lot of cranking to start. Put your foot on the throttle and start it and fires up fairly quick due to more air being available when it cranks over.

Want to experiment, swap carbs between the bikes. See if the problem follows that carb.
I swapped out my DIY exhaust for the stock muffler because i didnt have time to mess with the brackets and all of that since i had it all apart and the bike started how it should so i guess i will leave the stock one on...