Choking Engine During Acceleration

[crazydj]

Hey guys!

 

As stated above, my bike is basically choking when i open my throttle. This started happening mildly a few days after i went to replace my magneto coil, which was a few weeks back. I dont ride my bike as often recently. But now, it has become so bad that i have massive difficulties even reaching 80km/h on the expressway. Simple pick up from traffic light is so horrible to the point where i can feel the bike is close to stalling. I basically have to open full throttle to move at the same speed as the car.

 

I think i'll list out the symptoms for easier reading.

 

Symptoms

1. The choking during acceleration started out a few days after i replaced my magneto coil.
   
2. When it started, i had to open and close the throttle, or a few seconds later, it would just disappear by itself, giving normal power delivery. This will come back again a few minutes later, especially during start/stop traffic.
   
3. During deceleration when i close my throttle, i commonly hear a loud and short hiss-pop. At first, i thought it was an exhaust blowback where petrol ends up in the exhaust. Then i realised it came from my air-box.
   
4. I replaced my air filter a few months back and check it periodically. Checks ok.
   
5. Opened up seat, checked air-box and intake, no blockage.
   
6. The clean air intake from air-box to carb is fine.
   
7. With air-box opened, revved engine and realised that the loud and short hiss-pop comes from the little engine oil breather hose connected to the air box.
   
8. Breather hose to air-box ok.
   
9. A significant amount of air is trying to come out from the tiny hose into the even smaller hole in the air box. Some engine oil comes out from that hole.
   
10. Opened up engine oil filler cap, revved and a significant amount of oil wants to splash out. Does not happen in the past where i can rev and not a lot of oil will splash out.
    
11. Noticed that with the engine oil filler cap removed, the bike revs perfectly, no choking, no blockage. Seems that the engine oil can breathe sufficiently now.
    
12. Engine oil levels, sparplug and air-filter are normal.
    
13. Clutch plates ok.
    

 

 

The feeling of the bike is simple to illustrate. Basically it feels that it is being choked. A similar feeling would be as if the bike is being over filled with engine oil. I do not think the mechanic overfilled the crankcase with engine oil when changing my magneto coil. Oil levels are within normal specifications after bike has been run.

 

I understand that internal combustion inevitably involves a small but continual amount of blow-by, which occurs when some of the gases from the combustion leak past the piston rings (that is, blow by them) to end up inside the crankcase. That being said, i did a top overhaul, replacing my piston, valves and rebored the top block in 2011.

 

I thought perhaps a separate crankcase breather filter would be a temporary fix in this case. Any ideas on what could be the matter guys? I was wondering where else does the engine 'breathe' which is causing this blockage. Really value your feedback guys.

 

Thanks!

Edited August 24, 2014 by crazydj

[tiku]

Did u go back to the shop and ask y? Change coil means got change eo? Is it too much eo ?

[Hydher]

Things that may cause it

 

Magneto coil(charging system) / Rectifier

Air filter(too much air)

 

However, I feel that you have too much engine oil?

Crankcase breather hose is being clogged.