Topic: The "Why am I building this?" bike - 1971 CB500 K0

[NobleHops]

Your compression readings are right on the margin. I'm personally not persuaded that a low mileage bike should need rings. More likely, it needs a good Italian tune Hp after having sat for a while (which a 40+ year old low miler must have endured). Compression readings are a glimpse and not terribly specific to exact conditions unless 1 cylinder is dreadfully out of spec.

My suspicion, and it's only a suspicion, is the rings may well be gummed up due to poor state of tune when last run and sitting time. I'd tune it, run it for 300-500 miles. Change the oil and re-test it. A vacuum gauge would be another diagnosis to determine cylinder health at that point.

Food for thought.

I like it. We need to clear-tube test the carbs I think, and then this is exactly what we will do. No harm in trying this.

Any thoughts on the wisdom or lack thereof of putting a couple ounces of MMO in each cylinder for a few days, see if that limbers up the rings? Or (perish the thought) Seafoam?

[calj737]

SeaFoam "Deep Creep" is pretty good if you get the motor hot beforehand. Else, I like Kroil. It's far more effective in my experience at freeing up rusted/gummed up rings.

[Stev-o]

I agree with Cal [which I dont always do!]  Do you have genuine brass in the carbs?

PS.  Received the airbox yesterday, thanks again.  I owe ya....

[NobleHops]

I agree with Cal [which I dont always do!]  Do you have genuine brass in the carbs?

PS.  Received the airbox yesterday, thanks again.  I owe ya....

Unknown, actually. Harisuluv rebuilt these for me a year or more ago, and I do not recall. I think he would have said something if they had kits in them, and he does not really use kits.

We worked on the bike some more this morning, and had some odd running issues where it was instantly sooting up the plugs, and then 1/4 totally crapped out. In testing the points we learned that the 1/4 set had power at all times, which seems to indicate a short from an insulating washer. Coils and wires are new, coil power measured and the coils ohmed perfect. So we ordered a complete Honda points plate assembly, and now the bike has totally new ignition. Take THAT!

More as we know it.

[calj737]

And did you use resistor caps or resistor plugs? Odd that only1/4 would be an issue, if so I'd suspect the condenser.

[NobleHops]

P.S. We clear-tube tested the carbs too, and they looked like this:





They seem a skosh low to me. Thoughts?

N.

[Stev-o]

Left one one 2nd pic is a "slosh" low but dont think its your issue

[NobleHops]

And did you use resistor caps or resistor plugs? Odd that only1/4 would be an issue, if so I'd suspect the condenser.

Did not use resistor plugs (D7EA), caps are resistor NGK from 4into1.

http://4into1.com/ignition-coils-and-caps-honda-cb350f-cb400f-cb500-cb550/