Hawk 250 decided to retune itself?

sevndaythry · 12-19-2015, 09:57 AM

So about a week and a half ago I ran out of fuel earlier than expected (guess I'm getting more comfortable on it), and had to switch to the reserve. I went straight to a gas station and filled her up and didn't think anything of it. seemed to run normal the rest of my ride to work (had spots of weak power like it was running a bit lean). on the way home later that day the weak power spots seemed to be worse, so I took the stock carb off and sprayed it down with carb cleaner I never removed the bowl(didn't want to drill it). It was late so I didn't test ride it.

The next day we were heading out for a ride and it started driving like absolute garbage. seemed to be able to throttle through it, but don't have any useable mid range, super low or WOT. We hit some trails and did some wheelie practice other that limited throttle range the bike rand "fine".

The next day we had plans to pull the carb and drill the bowl off. Did that, cleaned the carb, had problems with the gasket swelling (anyone know how prevent this?) ended up having to remove some of the O-ring bowl gasket to shorten it.

To make a week long story shorter:

After putting it back together and many disassembly/reassembly iterations later I have diagnosed that my needle jet has grown in size all by itself.

The bike Idles fine. From 1/4-5/8 the bike is rich as all get out. 5/8 and up feels fine(might be a little lean, or only make 14hp).

I have made many adjustments to the pilot screw and none seem to have any effect.

Im almost positive my problem lies in the transition from pilot circuit to main circuit. But what would cause an unmodified bike to suddenly change like that?

I have a rebuild kit for the keihin clone on the way, and a mikuni clone coming as well. Its a race to see what gets here first. This has been so frustrating, and the worst part is I can't even go for a ride to relax

Problem Update:
Check your air Filter for restrictions. Mine was soaked in oil starving the engine of adequate airflow.

12-19-2015, 09:57 AM	#1
sevndaythry Join Date: Nov 2015 Posts: 44	Hawk 250 decided to retune itself? So about a week and a half ago I ran out of fuel earlier than expected (guess I'm getting more comfortable on it), and had to switch to the reserve. I went straight to a gas station and filled her up and didn't think anything of it. seemed to run normal the rest of my ride to work (had spots of weak power like it was running a bit lean). on the way home later that day the weak power spots seemed to be worse, so I took the stock carb off and sprayed it down with carb cleaner I never removed the bowl(didn't want to drill it). It was late so I didn't test ride it. The next day we were heading out for a ride and it started driving like absolute garbage. seemed to be able to throttle through it, but don't have any useable mid range, super low or WOT. We hit some trails and did some wheelie practice other that limited throttle range the bike rand "fine". The next day we had plans to pull the carb and drill the bowl off. Did that, cleaned the carb, had problems with the gasket swelling (anyone know how prevent this?) ended up having to remove some of the O-ring bowl gasket to shorten it. To make a week long story shorter: After putting it back together and many disassembly/reassembly iterations later I have diagnosed that my needle jet has grown in size all by itself. The bike Idles fine. From 1/4-5/8 the bike is rich as all get out. 5/8 and up feels fine(might be a little lean, or only make 14hp). I have made many adjustments to the pilot screw and none seem to have any effect. Im almost positive my problem lies in the transition from pilot circuit to main circuit. But what would cause an unmodified bike to suddenly change like that? I have a rebuild kit for the keihin clone on the way, and a mikuni clone coming as well. Its a race to see what gets here first. This has been so frustrating, and the worst part is I can't even go for a ride to relax Problem Update: Check your air Filter for restrictions. Mine was soaked in oil starving the engine of adequate airflow. Last edited by sevndaythry; 01-10-2016 at 09:55 AM. Reason: added solution to end of problem.
	0