A little closer - still rich.

[maireeka]

Well I found out the reason my cb125s was fouling plugs so bad. There is supposed to be a spring and an 0-ring installed with the pilot screw! they weren't there when I got the bike, but I've installed some since.

I also lowered the float height a little more.

Pilot screw is still all the way in...

She is firing up on the 1st or second kick (indicates too much fuel, since choke is not installed on the carb)

I have had a nice chocolate spark plug 1 time, but after riding it for a few minutes she's back to fouling them out (black sooty)

I'm using NGK spark plugs.

Any thoughts? carb tuning is a bitch!!

I have ordered new points in hopes that a weak spark is causing the plug to foul easily.

 

[loudest143]

When you say pilot screw, are you referring to the fuel/air mixture screw? If so, all the way in is definitely wrong. Are your jets the right size? I mean all of them? (BTW, I'm not sure what they should be, either.)

I'm thinking that if your floats are correct by the book, and your mixture screw is all the way in, too much fuel is still getting through, right? I might say check the jets to make sure they match your air filter/exhaust setup. Refer to your manual, or website information database of choice.

Only other thing would be low spark, but if this thing was running well before, I'm not feeling an electrical issue here.

loudest143

 

[maireeka]

yeah, air fuel screw. I know it's wrong but it's the only way I can get it running right lol.

This carb only has 1 jet. Main is 110 (stock) and I'm running stock exhaust and open carb at the moment. (carb comes off too often to worry about hookin up the air box)

If the carb is open, that should lean it out, not richen it right? since more air is getting in than it's jetted for?

It's gotta be float bowl or weak spark I think, my points should be here in the mail soon and we'll see if that makes a difference.

 

[loudest143]

http://cgi.ebay.com/ebaymotors/Honda-CB125-CB-125-CB-125-Benly-Napco-Carb-Rebuild-Kit_W0QQitemZ220391945451QQcmdZViewItemQQptZMotorcycles_Parts_Accessories?hash=item220391945451&_trksid=p4506.c0.m245&_trkparms=72%3A1205%7C65%3A12%7C39%3A1%7C240%3A1318

This kit is pretty comprehensive, so I'm just using it for reference material....

You definitely have more than one jet. Pilot jet, low rpm/idle part of the circuit, Needle jet, middle part of the circuit, and Main jet, high rpm part of the circuit. All three could be contributing to your richness. Of course if we were talking about chocolately richness, we would all be happy right about now. ;D I'm gonna recommend that you take a look at your other jets..... The pilot jet is (big assumption here) probably okay, if the bike starts well, idles well, and is good on starts. BUT, the needle jet, well, it could be raised too high, and dumping too much fuel into the carbs in the midrange part of the circuit. (when I say circuit, I'm referring to the carb as a full UNIT, or circuit, which has 3 parts, low, middle, high rpm ranges.)

Running without an airbox or air filter is something that should lean out the circuit, at least a small amount. I'm guessing that the needle is where you should look next. Find out what the stock setting should be for it, and move them back, if they are out of place. (little circlip holds them in place on many carbs.)

Also, pull your float needle, the little guy that sits under the tab you adjusted to re-do your float height, and clean the snot out of that hole. A stuck float needle could completely hose your adjustment you did. Remember, little tiny bits of ANYTHING can screw up the carburetion circuit, so make sure you've got a good fuel filter and new hoses...... Replaced your o-rings and gaskets already? They can cause small leaks. (been there!)

I would like to comment that you'll become the neighborhood expert on vintage carbs when this is all said and done.

http://www.dansmc.com/carbs.htm If you haven't read this page, I found it quite helpful in laymans terms.

loudest143

 

[maireeka]

110 main is definitely the stock jet for this bike.

It does not have a pilot jet, just a pilot (fuel) screw. This is a 78 cb125s.

Check out the diagram

Needle is currently at highest clip, was at 2nd from top but it's at top now.

I'll put the airbox boot on and see if that makes a diff.

Points should be here today or tomorrow, I was lookin at the old ones and they were pretty worn. Perhaps a stronger spark will make a difference.