problem with starting

[leonidasthegreat]

i have a big problem.. my cb1 dosn't start. i think the problem is electrical because the fuel pump dosn't work.  i was connect th fuel pump directly to the battery and it was been working....

has anyone an idea for what is the problem ??

[marty]

first, check the fuse...

then, is there a relay for the pump? voltage to the relay? take a voltmeter and test across all the junctions... should let you know where/what the problem is.

[BrotherEng]

I've also had a problem with starting and did the same check out. Does anyone with a working bike know if they "hear" the pump working when the ignition is turned on? I put a voltmeter to the line that comes out of the Fuel Cut relay. I have 3 +12V readings on the wires(Bu-Y,Y-Bu, and Bl). The one wire that leads from the Fuel Cut relay to the pump is 0V(Bu-Bl). It doesn' t give power to the pump. I've just replaced the relay and still have the same result. Can anyone get me the correct voltage readings to the relay and pump when the engine is one?

[Car2Slo]

I believe the bike has to be running for the pump to be on.   It's a safety mechanism to prevent the pump from dumping fuel in an accident. 

I tested my fuel pump by disconnecting the outlet hose (going to carbs) and pouring into a container.  When I crank the motor (try to start) the pump pushes fuel out, putting the bike in the on position didn't do anything by itself.  * be careful if you try this.

P.S.  The electricl diagram is on the last few pages of the service manual.  I posted on this forum for those that don't have it.

[Car2Slo]

Looking at the wiring diagram this is what I can figure out (if my tracing isn't bad)

Fuel Pump cutoff relay wiring (4 wires) - fuzzy color codes so excuse if wrong

In sequential order

1.  Bl/Bu - goes to fuel pump.  Supplies 12v positive when all is good.
2.  Bl  - power cable, goes to fues box (line also feed starter switch)
3.  Y/Bu - goes to spark unit, 1, 4 ignition coils.  Trigger when bike is sparking (this may be pulsed signal.)
4.  Bu/Y - goes to spark unit, 2, 3 ignition coils.  Trigger when bike is sparking (this may be pulsed signal.)

I don't think you'll be able to measure the spark unit trigger voltage for the relay (depends how the signal looks).  You should see 12volts on the 2nd (Bl color) line.  When all is good you should see 12v on the fuel pump line (Bl/Bu color) but most likely only when the bike is running. 

To remove the posibility of fuel cutoff relay problem you can hot wire the fuel pump directly to positive 12V (ie. disconnect fuel cut relay and jumper 12v to Bl/Bu to fuel pump).  Many riders do this to get their bikes home in emergencies you'll only be eliminating the fuel cut-off safety feature which you can repair later on.

[mechdziner714]

Threse bikes dont run for sh!t if you let them sit for a while. Just keep trying to start and ocaisionally twist the throtlle, eventually she'll start. Ride it every day and its not an issue.