Electrical or Fuel, I don't know what is up.

Tom Cat

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Webster Groves, MO,USA

Re: CB 175 k6 1972
Here is a problem that has got me stumped.
I have been riding, albeit not too often, this little Honda. I put it together from boxed parts and the help of a student.
I rebuilt the carbs which are supposed to be good copies of the originals. Adjustments are on the same side so you need a long screw driver to adjust the left carb, but otherwise seemingly the same. I followed the steps of adjustment and they make sense,(thanks to many of you) and it idles very well an 1300-1500. The problem is carbon on the spark plugs after a 30 minute ride It begins to cut out. Too rich on the fuel side or light or ill timed/weak spark. I went through the timing, We are dead on F when my test light goes on ( attached to ground and the points) and it is gapped correctly. My Ohm meeter reads from the stator Pink to yellow 14 pink to white 12 white to yellow 8 at 1400 rpm. not great but seems to charge the battery.
Ideas anyone? Where would you start?
Tom
 
What air-cleaners are you using?...A picture if not stock.....
Plugs of correct heat range and gap correct?
Resting battery voltage?......Battery voltage after the 30 minutes riding?
Is FULL advance timing correct?
Which slot are the carb needles E clip in?
What RPM are you revving to/riding at?
 
Tom Cat said:

Re: CB 175 k6 1972
Here is a problem that has got me stumped.
I have been riding, albeit not too often, this little Honda. I put it together from boxed parts and the help of a student.
I rebuilt the carbs which are supposed to be good copies of the originals. Adjustments are on the same side so you need a long screw driver to adjust the left carb, but otherwise seemingly the same. I followed the steps of adjustment and they make sense,(thanks to many of you) and it idles very well an 1300-1500. The problem is carbon on the spark plugs after a 30 minute ride It begins to cut out. Too rich on the fuel side or light or ill timed/weak spark. I went through the timing, We are dead on F when my test light goes on ( attached to ground and the points) and it is gapped correctly. My Ohm meeter reads from the stator Pink to yellow 14 pink to white 12 white to yellow 8 at 1400 rpm. not great but seems to charge the battery.
Ideas anyone? Where would you start?
Tom
Click to expand...


Thanks guys for getting back,

Sorry for my slow response, I start teaching in two weeks and the school is nuts.
The Spark Plugs are NGK D8HA
I ran the bike for 20 minutes . Prior to starting it the battery read 12.10 and after about the same. I did notice my front break light switch needs to be readjusted. This handle was broken in an apparent crash the bike and rider had before me. I noted on a previous site, with help, of bending back the back break peddle and foot rest and having my welder recreate part of the handle that had broken off.. Bad hit. The voltage meeter went down to 11.8 at 1400 rpm with all lights on and break light on. at 3000 it emerged over 12 volts again topping out at 12.8 at 3000 rpm without lights. There are only foam cylinders for air filters, I am still trying either design or find original air filters. I don't know what you mean by "E clip" and Full advance timing. I replaced the spark advance a couple of months back, and set the timing light to go on at the F with the proper gap.
What octane should I be running in this bike? My F650 uses 93 so I assumed it was the same.
 
A 12 Volt battery that ONLY reads 12.10 is dead......Normal (good battery) reading is 12.6 to 12.7 Volts at rest.......13.2 ish immediately after charging......
During normal running, the DC output from the re-charging circuit (rectifier and regulator) to the battery is in the high 13's to 14+V at high revs.......
Expected idle speed alternator output should be 18 to 20 VAC (P/Y) and 16 to 18 VAC (P/W)........W/Y is meaningless as far as output......
 
Thanks guys for getting back,

Sorry for my slow response, I start teaching in two weeks and the school is nuts.
The Spark Plugs are NGK D8HA
I ran the bike for 20 minutes . Prior to starting it the battery read 12.10 and after about the same. I did notice my front break light switch needs to be readjusted. This handle was broken in an apparent crash the bike and rider had before me. I noted on a previous site, with help, of bending back the back break peddle and foot rest and having my welder recreate part of the handle that had broken off.. Bad hit. The voltage meeter went down to 11.8 at 1400 rpm with all lights on and break light on. at 3000 it emerged over 12 volts again topping out at 12.8 at 3000 rpm without lights. There are only foam cylinders for air filters, I am still trying either design or find original air filters. I don't know what you mean by "E clip" and Full advance timing. I replaced the spark advance a couple of months back, and set the timing light to go on at the F with the proper gap.
What octane should I be running in this bike? My F650 uses 93 so I assumed it was the same.

So I think I posted this in the wrong place. I also was looking through the oem sheets at Bikebandit for the carb needles E clip. But could not find it.
 
Thanks again. So a new battery, and possibly the stator? My readings are so much lower than what you cited so I figured it was the stator. But the battery could be the cause, or is this the Stator or regulator? It seems to me all connected and hard to decipher what to buy. My other bike had scorch marks on the leads to its regulator and a melted fitting, smoking gun. This one is tuff.
Thanks for your help
 
Tom Cat said:
Never thought of that. I took it off and could blow through the hole. Is there a better check?
Click to expand...

If the vent is blocked or simply not working, as in some pattern fuel caps, you'll hear a hiss when the cap is removed. Left in the sun, tank gets pressurised, hiss of escaping vapour when cap is removed.

Vice versa, when bike is run, fuel level goes down, partial vacuum in tank develops, stops fuel flow, engine stops. Hiss of air re entering tank when cap removed.
 
I will check, at work now. Today, of course, is the only not hot day in St. Louis, so I can't just pull the cap and listen. Would a lack of fuel flow cause carbon on the spark plugs?
 
You can also test the cap for venting by draining the tank with the cap in place. If it's not venting the fuel flow will stop because of vacuum inside the tank.
 
Richard Pitman said:
If the vent is blocked or simply not working, as in some pattern fuel caps, you'll hear a hiss when the cap is removed. Left in the sun, tank gets pressurised, hiss of escaping vapour when cap is removed.

Vice versa, when bike is run, fuel level goes down, partial vacuum in tank develops, stops fuel flow, engine stops. Hiss of air re entering tank when cap removed.
Click to expand...

Outside of the plug conversation I had similar issues- 40 miles into a ride it would start to sputter. Unplugging the gas cap vent helped but a secondary issue was a flow restricted petcock due to rust particles partially blocking the outlet tubes. All issues resolved after swapping out old for new.
 
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