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Discussion Starter · #1 ·
Hi all,
Hope you can help
Have 3 Manuals for the CB250/CB350 k4 and going mad. Been reading threads and not sure if electrical issue or not.

Ignition timing is good, the points and plugs arc on both sides. Compression is also good.
Carbies need a kit and it’s on its way.
Some questions and your advice would be greatly appreciated.

1. What’s the correct float level measurement? (Manuals go from 18.5mm to 23mm-25mm. I think my RHD carbie float either has a hole or measurement is wrong.

2. When I start the bike RHD exhaust is cold and don’t think RHD is firing correctly although sparking and arc is nice on both sides

3. When I put the points cover on, bike does not start (paper gasket has small tear)

John
PS am in Sydney, Australia
 

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Is the Right Plug WET after trying to Start?
That will indicate if you are getting fuel to the cylinder.

Sounds like you are shorting out the points with the cover, check the angle of the wire connections.
And are the wires are on the inside or outside of the stud/nut?
 

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Discussion Starter · #3 ·
Is the Right Plug WET after trying to Start?
That will indicate if you are getting fuel to the cylinder.

Sounds like you are shorting out the points with the cover, check the angle of the wire connections.
And are the wires are on the inside or outside of the stud/nut?
Thanks for responding will check tonight
 

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Discussion Starter · #4 ·
Thanks for responding will check tonight
Hi Yendor, noticed that lhd points cable was poking out. Got up this morning to discover that all my fuel had come out of my overflow amd onto the ground. Think maybe needle and seat + float issue. Still not sure why am not firing on right. Might be ignition coil or condenor. Points and plug cables shkwimg good arc though on both sides.

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The floats and needle valves on these old bikes never were real great. That's why it's recommended to turn the petcock to off whenever the bike is shut off.

You also need to check your oil for fuel contamination, a common problem with overflowing carbs. Better yet go ahead and change the oil, just in case. Cheap insurance.
 

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Discussion Starter · #6 ·
Thanks guys, finally got back to this. Put a kit though the right hand one and it fires up now. Getting some popping on the right now.
Lubed up all the parts and set the float hight to 23mm.
Timing is great, but elements of running rich or starving of air. Would it be spark plugs or need to kit the left (runs perfectly)?


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Discussion Starter · #7 ·
And yes petcock is old. Getting a kit to replace the old ones as they are showing signs of wear.


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The float valves only need to seal the fuel more than what the engine consumes at idle, so I guess if they leak slightly, it is not problem... Later motorcycles mostly had vacuum operated fuel valves that only opened when the engine was turning (because float valves do not necessarily seal 100%).

I've made a cork gasket for my fuel tap. It seals very good.
 

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Points should not be "arcing", they will arc/spark a bit, but not like the plugs. They should not arc/spark brightly. Points wearing quickly and seem "white" ??

Bad points on bad cylinder ?

You know how to set the points up, dwell meter, strobe, radio etc., until you know feeler gauge "feel". Auto advance all ok ???

Valve clearances all ok etc. ?

Carb rubbers all ok ? you know of cmsnl ?
 

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Pick a spark plug checker at your local auto parts store. $6.00 t0 $12.00. Make sure your plugs are new or clean and gaped. Timing is correct. Put the checker between the plug wire and the plug and turn the motor over and it will tell you if your plug is firing in the cylinder. Then you can work on the carbs knowing the plugs are firing.

Just a thought.

Bill
 

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Discussion Starter · #11 ·
Thanks Bill I have one and put new plugs in.
Got my carb kit from common motor. Both cylinders fire, but not holding idle. No air gaps. Synced and idle screw is at 1 1/2 full turn and trying to go clockwise to gain acceleration. Any ideas? I am commited to make this run


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