Carb tuning caused bike to die?

[ficklepickle]

Hi guys, weird experience today while riding home. Firstly, I ride a Honda NSR150SP with a ported Keihin carburetor and K&N Pod Filter.

 

Yesterday I bought a new original Honda end can to replace my old scratched and carbon-filled one. I just took out the old exhaust and fitted the new exhaust and started riding without adjusting the carburetor settings. The new found power was addictive.

 

In the afternoon, it was fine. However, tonight while riding along Holland Road, it got pretty cold and I did give the throttle a proper working out while going out the flyover and suddenly felt that I was losing drive and twisting the throttle did nothing. I quickly signalled to the left and slowed to a dignified stop at the side of the road. Perplexed and worried that I may have encountered a piston failure. I gave it about 5 minutes rest time and just tried kick-starting it again. It worked! I was ecstatic. Rode on for about 2kms more and it died again. Waited and kick-started it back to life. Then from there was another 10km back home without any problems.

 

My theory is that the stretch of road where I was riding was pretty cold and after riding in normal temperature again, it was fine. Was the cause of the dying due to unadjusted carburetor settings? Thanks for all your input!

[LeftCoast]

I'll take a stab at the possibilities here (feel free to correct me here)

 

1. The aftermarket carb was designed to have an improved intake airflow.

 

2. The ported carb probably had improved performance slightly. But it couldn't perform to its fullest expectation because the entire system (intake, combustion, exhaust) was impeded at the exhaust section by the dirty end can you had.

 

3. When you changed the end can to a newer one, the fuel-air ratio changed in that the "air" component of the equation is now larger i.e. you now have a larger airflow. This imbalance meant you now are running lean.

 

4. Taking hypothesis #3 into mind, during the day the bike still runs fine despite the slight imbalance but when nighttime came and the air became denser, the strong surge of intake air caused the fuel-air ratio to be even more lean, causing loss of power.

 

Again, these are my hypothesis. I'd like to hear your side of the story if possible

Edited February 10, 2011 by LeftCoast