The Mordern Bajaj Chetak Rides One
Only fill the tank to the first ring at the bottom of the filler neck. Look inside you will see that between the bottom ring and the top ring, there is a vent to the emissions system. Ff you overfill, the excess gas goes down that tube to the emission can that is filled with charcoal and once that gets wet it cuts off the air to the tank causing a lock the gas in the tank wont move without air. This causes sputtering, hesitation and rough running; even quitting.

In the early days, riders with this problem resorted to drilling holes in the gas cap to prevent this vacuum lock, but most found the emissions hose easy to disconnect to relieve the lock and learned to keep the gas level below the ring. 

From time to time riders encounter symptoms they describe as "fuel starvation."  Essentially, the scooter runs and is rideable but seems to have no power or lose power at higher speeds.  Sometimes this  actually is fuel starvation caused by a vacumm lock created in the gas tank.  Please understand that the Chetak gas tank is not very high above the carboretur so there is very little gravity force to feed the carb,  Almost any blockage or kinking of the fuel feed lines can cause this symptom.  But, there can be many other causes - a bad spark plug cap, a bad CDI, and simple loose ground.  The following list of checks can be performed to rule out various causes:


1. Check for a solid ground wire on back of the engine housing, if this ground
wire gets loose, inconsistent electrical performance results.

2. Get the right spark plug:

Champion PL7YC (OEM but impossible to find)
Champion L87YC
Bosch W5BC
Bosch W5BP
NGK BP7HS. (Easiest to find also as it is also used in small yamaha outboards)

3. Try replacing the OEM spark plug cap with an NGK resistor cap, the OEM sparkplug
cap has a history of problems that cause crappy running symptoms identical to
your description. 

4. Replace the CDI, a "New Racing CDI" runs about $14.00. All cdi's do go bad over time.

5. Check the main fuse while you are at it. The bike will run with the fuse
blown but no headlight is usually the one indication that the fuse is blown. I
have dealt with lots of electrical problems related to this.

6. You may want to purchase a spark tester - a inexpensive device that fits
between cap and a ground and shows you a spark for every revolution. Inconsistent of spark

at high speeds could be
caused by 1-4.


1. If you ran out of gas immediately before the problems, this could indicate that you

 just sucked every bit of debris and varnish into the fuel tap screen and the carb. 
Clean the carb. Check the color of the float - white is good, brown is probably an indication
 that the float leaks and is sitting in crappy gas all the time. Check all fuel line
connections to the carb and check for kinks in lines. Empty tank and fill with
clean (preferably ethanol free) gas (use fuel stabilizer religiously unless you
run the scoot every day). Blocked carb valve, carb jets, carb ports, or a
sinking carb float can all cause "fuel starvation symptoms." 

2. Test fuel flow from fuel tap to carb. Close the petcock, pull the end of the
line off at the carb, open the petcock and watch for a vigorous flow of fuel
into a can. Move the petcock to the reserve and you should get the same
stream.If it is a small stream it is blocked at the fuel tap and you will need to
pull tap and clean it out.

3. Pull off the evap line from top of tank, blow it out to prevent any blockages
there. At high speeds, this line has been known to cause a vacuum lock in the
gas tank and prevent the gravity fed fuel flow at high speed.


1. Inspect your filer element, you may find oil in it from when the bike has
been lowered onto the battery side or you may find your missing gas - who knows?
But if there is stuff in there, then poor running will occur.

The Modern Bajaj Chetak Rides On The Modern Bajaj Chetak Rides On