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Old 1st August 2010, 12:34   #1
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Default Bajaj sunny stalling problems

I have a 1998 model bajaj sunny zip. Problem is after running for approx 2 to 3 kms the engines starts to die as if no fuel is reaching the carb. The moped eventually stops and has to be started by applying choke for approx 3 to 4 mins, but still it runs again for 2-3 kms before dying again. I am facing this problem for last 3 months. I have done the following
1) Cleaned carb muliple times using kerosene and STP carb spray. The jets looks fine and the jet holes are not blocked.
2) The idling and fuel/air ratio screw in carb was not disturbed/adjusted during cleaning.
3) The float pin was changed to new one.
4) 6 days back the moped would not start. Removed and checked the spark plug. No spark. Replaced with diff part number and checked spark. Spark excellent, but still now problem comes after 10 kms or so.
5) When choke is applies engines speed varies a lot inspite of throttle kept constant which is weird. One second it is idling next second at high RPM and the speed vary cycle continues.
6) Checked fuel line from fuel cork to carb. Line clean and flow excellent in on position.
7) changed fuel by filling from diff petrol pump. No result.
8) Breather hole in plastic fuel cap O.K.

The authorised bajaj dealer does not accept it for service since he says no spares available. But my guess is the float is getting stuck and hence no fuel. Sometimes the vehicle is OK in idle but engine dies when throttle increased. Any suggestions welcome.
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Old 1st August 2010, 19:09   #2
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We too have a sunny but thats a 94 model. It had similar problems as your but i got it sorted out.
Check the following:
1> Spark plug gap.
2> 2T oil your using. I used to fill in Castrol super 2t oil in mine.
3> Check the float and float pin. The float is plastic so it tends to crack with use.
4> Check the air fuel ratio. Mostly i used to get this set at every service.
5> Check the fuel tap filter, get cleaned if possible.
6> Had got my spark coil replaced as it was leaking current. So u could have that checked as well.

This is all i can think of as of now. Good luck!
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Old 1st August 2010, 19:45   #3
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Originally Posted by tejasnaidu View Post
8) Breather hole in plastic fuel cap O.K.
Pls, can you tell how this was being checked. Appreciate a detailed answer on this one. Tks.

Originally Posted by tejasnaidu View Post
The authorised bajaj dealer does not accept it for service since he says no spares available.
Pls don't take NO for an answer on this one. Scream, shout, threaten, beg, build rapport or do anything with them to have them accept your vehicle for service. In addition, did you know that the dealers can place order with Bajaj for the parts & Bajaj should supply to their dealers. In addition, you can check with any local reputed automobile spare parts shop to find spares for you.
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Old 2nd August 2010, 12:20   #4
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Regarding breather hole. There are 2 big holes at the bottom and one hole at top of plastic cap. When held against light you can see through the holes. There is sufficient space for air to flow. Will post pics if needed.

Ripper thanks for your suggestion.
1) I used to use castrol 2T (red can) till recently. Now using servo.
2) Regarding air/fuel ratio, it was set by the bajaj technician many years back during authorised service and since has not been tampered with since there was no problems. Air/fuel setting is very critical i do not touch it or do not allow local mechanic to touch it.
3) Regarding HT coil will change and see as i have one in spare.
4) Will remove the carb again and check the float for pinholes etc. No visible cracks during last cleaning.
5) where is the fuel tap filter located. Last saw 2 pipes(Main/reserve) from tank to fuel cork and then 1 pipe to carb with no filter in between.
6) Manual recommends Mico W4AC or W7BC plugs. They were not available hence used WQ7BC4 plug normally used for CNG/Petrol 4 stroke auto. Q denotes quick heat. Am waiting for recommended plugs from mico dealer but it will take time. Then will check gap with feeler gauge.

Took the moped out on sunday. Initially started the moped with choke on idle for 2 mins then drove 1 kms with no problems. Acceleration was great with top speed of 45 km/hr which is very high for sunny. Parked for half hour. During return 1 km journey the same fuel problem came up.
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Old 9th August 2010, 16:58   #5
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Please try to decarb the silencer .
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