Topic: Unknown problem please help

[Hush]

This isn't going to end well is it guys!

[Jay B]

This isn't going to end well is it guys!

Time will tell. Sounds determined to succeed.

[750K2]

he's at it pretty hard
E string is god's gift to honda carbs

[crazypj]

Main jet should screw in

 Its a press in main jet with the spring steel plate holding it on 78F, the 78K got the weird carbs
pilots should be screwed in on F and pressed on K
 still sounds like the original problem is blocked tank cap vent.
Squigly, your right about the hose on bottom of tank, its to drain water from recessed area around filler cap.
 could you g a picture of bike posted?
Did you try running with fuel tap on reserve position?
PJ

[SquiglyUpright]

Yeah I'll get some pictures up when I get off work today. I'm sure there is air getting through the air cap vent, i tested by just blowing through it, but air definitely went through, whether or not more air should be able to get through or not i have no idea.

So i took apart the carb last night, and got it all cleaned and put back together around 11pm, and put it back on the bike, but it was late and i only tried to start it up once or twice to no avail.

Thanks for all the help guys, I'll post some more stuff when I get off, around 3:30 pacific time.

[crazypj]

If you could blow through the tank cap hole it should be fine.
 I'll do some more thinking 
PJ

[TwoTired]

I'm surprised you aren't complaining about how hard the slow/pilot jets are to remove.  You sure that's what you removed?  You also have to prove that fluid will travel between all four holes in the carb for the pilot circuit, which are:
The pilot jet, the pilot air jet, the Idle Mixture Screw (IMS), and the carb throat exit hole.  When removing the IMS note there is a spring, a washer, and an oring in there as well.  It needs all those parts.

Anyway, a paper clip is the wrong tool for clearing the slow jets. Too big.  Pay attention to the actual orifice size.  A #42 jet is  0.42mm in diameter or about  0.016 inch.  You've got a paper clip that small?
You must be able to see light through the jet when it is clean.

Further, you are working very fast on this bike.  It needs the air filter on to run right.

The 78 PD carbs have a screw in main and press fit pilots.  The EPA/Honda didn't want the pilots to be tampered with.  Rather short sighted from a maintenance standpoint.

Cheers,

[SquiglyUpright]

Yeah I didnt have any trouble with the slow jets coming out. I'm 98% sure I got the right ones. They were gold colored, bigger on one end, and smaller on the other with tiny holes in the side. Kind of like an old chain gun. I could see light through them and I rotated them while looking through it in the light to see if i could see anything on the sides, but I did run out of compressed air, and am not sure if the passage way where it unscrewed from is completly clear, I tried blowing through it with just my mouth, but it was hard. Is that more likely where the blockage would be? They seemed cleaned, but in truth I dont know for sure.

Yep the air filter is in. I'm anxious to get home now and get it running. If it doesnt start up, I guess i'll pull the carbs again and get some more compressed air for those passage ways.

[TwoTired]

Maybe a picture will help?  It's the part in the tool jaws.

[SquiglyUpright]

Yep, that is definitely what I pulled. They came out really easy though, just a fairly light twist with a flat head screw driver and they unscrewed.

[TwoTired]

WHAT?

PD carbs don't have screw in pilots.  And, that was the only carb offered in 1978.  What carbs do you have?  Is it really a 78?  What country are you in?  Do you have a choke knob at the bars?

[SquiglyUpright]

I'm in the U.S. I'm sure it is a 78, I have the original title and things, not sure on the carbs though, I will have to take a look when I get home, but i think they are original.

The slow jet looked like the one in this picture

[TwoTired]

It should say so on the frame's headstock what model it is.  It doesn't matter what is on the tittle for a reference to the parts that belong on the bike.  DMV could care less if they have that information right.  If it is a 78, then your bike has been retrofit with earlier carbs, no question.  The picture you've posted is NOT the PD style carbs that should be on that bike and what I assumed would be you your bike.
The picture you have posted is for a carb style used on the earlier 550/500 bikes.

Look on the carb mount flange top right.  They should be stamped with a number; 627a or b, 022a, 069A, or 087a.

These carbs can be made to work on your bike, but they are non-standard.  Post the Jet numbers.  The main jet for the type of carb pictured has a leaf spring that holds the main jet in place when the bowl is installed.  If indeed you have that carb type and no leaf spring, then you have parts missing and I would carefully review/notate what internal parts and settings your carbs have.

What does your exhaust look like?  How do you know you have the stock filter type?

[750K2]

good god TT..what on earth do you do for work?? human computer?

[TwoTired]

good god TT..what on earth do you do for work?? human computer?

Sorta, I guess.  Electronic engineer was my trade.  Retired now.  Hard to be successful in engineering if you can't remember facts, details, concepts, and methodology.

These days, I'm just underachieving.

[SquiglyUpright]

OK so I took another look at the carbs, and pulled them off again. The number on them is 627b. I pulled plugs three and four and both were very black. I took a couple of pictures too. Sorry about the quality on the last two, my camera sucks/

[SquiglyUpright]

Ok carbs are coming apart. Take a look.

[Hush]

Yummy fluffy carbon, your carbs are getting gas alright, now you gotta figure out if its in the right proportions.
There should be a legal requirement on old Honda's, if you ditch the original carbs you need to tattoo it on the crank case...will stop new owners banging their heads against solid objects and considering Hari-kari.

[TwoTired]

Ok, so you have a hybrid bike.  627 B carbs were from a CB500 1972 or 73.  Your exhaust is not stock either.  The black plugs are no doubt due to improper jetting of the carbs for that assemblage of parts.  Those carbs were jetted for a 4 into 4 exhaust, stock paper air filter, and an engine displacement of 498cc.

For economy sake, I'd recommend you get a UNI NU-4055 foam air filter.  This is a reusable foam air filter that has a bit less restriction than the paper (especially and old used paper filter), that provides a bit too much choking action.  Settle on the filter you are going to use long term before dialing in the carbs.

The 627B carbs were set up with #100 mains, #40 slows, and the slide needle (I think) in the middle position.
If you are completely satisfied that the carbs are clean including those emulsion tubes (main and idle), then you need to find out if the carb internal setup is still in the stock configuration, jet number slide needle position, and Main jet size.
I think the #100 mains may work out OK.  But, the slide needle height will likely need a different position.  And, if you can't lean up the idle mixture enough with the Idle Air bleed screws, then you may need to find #38 Slow jets.

Any chance you are using D7EA plugs?  Get a couple spare sets to use while tuning the carbs for their current employment.  Be sure to check that all plugs have the same deposit condition.  Because what you do to one carb will be replicated to the other three.

You will want to do the whole tuneup process before dialing in the carbs (tappets, cam chain etc.), and you will need manometers to vacuum sync the carbs after changing slide needle height positions.

It should work out okay.  But, you've got some work ahead of you.  Do you have a test track available to do "plug chops" on?

The inside of your carbs do not look that bad, but this series of carbs has issues with the post around the main jet corroding. I can't see that in the pictures so make a close examination of that area.  Further, if the o rings on the main are at all hardened, they will not seal properly in place and excess fuel will leak past, around the metering orifice, making the mixture rich or erratic.   A new oring is recommended.

Cheers,

[SquiglyUpright]

ok well first off, thank you, and second sweet, I just bought the UNI NU-4055 air filter. I have no idea what number the main jets are, but the slow jets say 40 on them. And how do i change the slide needle height? and how do I know what to change it too. I have also already adjusted the tappets, and I'll go ahead and do the cam chain too.

I am using D7EA plugs, and I will get some more. They were very black, but it wiped off like it was burn residue or something. Does that mean it is running to lean?

[Sam Green Racing]

Black is running rich.

Sam.

[TwoTired]

The black soot are unburned hydrocarbons, meaning it is too rich.  The soot is conductive.  When the center electrode insulator gets enough of a coat on it, it shunts the spark away from the gap, causing misfires or no fire at all.

The slide needles are accessed under the top cap of the carbs.  The bolt to attach the slider actuator arm on the main shaft gets removed, and the two philips screws down in there deep get removed.  Then the arm and attachment linkage swivel up and the slide can be removed.  The needle can then be pushed out of the slide and you can see the clip positions.

Can you do "plug chops" at WOT using clean plugs?

[SquiglyUpright]

I can do plugs chops, not too familiar with it but i've read a little. What is "WOT" though? I just ran to autozone and bought new plugs so I will definitely do that tommorow.

[SquiglyUpright]

OK I got the slide needle out, and it says 272304 and there are five notches. It is currently on the notch second closest to the bottom. What would be the best notch to put it at, and what does it affect if it is lower or higher? thanks.

[Sam Green Racing]

A plug chop is done with the throttle wide open. WOT=wide open throttle.

Sam.