Topic: cb550f running at 10mpg

[tlbranth]

Terry, I'm guessing that the GL1500 isn't a points ignition.

That's right. No points.

[tlbranth]

Terry,
The stock SOHC4 coils are 4.8 to 5 ohm primaries that are switched by points.

Dyna offers coils in both 3 ohm and 5 ohm primaries.  The 3 ohm ones are intended to operate with their dyna ignition triggers.  But then, 3ohm and dyna-s draws too much power for use on SOHC4 bikes smaller than the 750.

Fyi

Cheers,

I put the 5 ohm Dyna coils on my CB750 along with Hondaman's ignition. Works nicely. I'd be too chicken to ever put a non-oem electronic ignition on a bike.

[TwoTired]

10 mpg on a 550 means it is using fuel at about a 4to5 times normal rate.

Black carbon is made by heating hydrocarbons without combustion., I.E. incomplete combustion with lack of oxygen or more fuel than available oxygen.
Spark lit it off but it couldn't completely burn.
No spark and the cylinder just stays wet with fuel.

So, focus on why the cylinder is getting too much fuel.

Floats first, verify the carb fuel level is correct.  If there aren't stock spec parts in the carbs, the book mechanical settings may no longer apply.  That's when clear tube method is of benefit.

Check oring seal, emulsion tube fit, exit jet dimensional wear, and bleed holes clear.

Check for drilled jets, pilot and main.

Note numbers and markings on metering devices.

"Prove" each passageway will flow and is clear of obstructions, including the air jet passagways.

Verify the carb venting system is functioning.

Don't expect the F model 069a jetting set up to operate well on engines that don't have the stock exhaust in induction set up.  The stock configuration was tilted toward a lean burn setup to meet demands of the EPA before the rules went into effect for mandate in 1978.  If your carbs are delivering too rich with open exhaust and pressure differential loss from an altered induction tract, the carbs are defective, imo.

Cheers,

[dave500]

that #4 carb bowl belongs on #1 or #2,the drain screw is on the wrong side.

just out of interest I run the 069a carbs with 40/100 jets on a 550 engine,stock airbox but decent 4-1 pipe,i don't consider them a lean burn carb at all I save that #$%* for the later pd crap carbs.

[Robbo]

The picture of the carbs that OP posted showed a bit of fuel in each carb overflow tube.

Float heights need to be re-checked.

Have you checked the make and numbers stamped on your jets yet?

Btw, that’s a nice looking bike.  You’re going to be so so happy once this gets all sorted out.


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[Deltarider]

The picture of the carbs that OP posted ...

Have I missed it? What picture?

[dave500]

it got deleted?

[Bru-tom]

I see my post from yesterday is gone?🤷🏻‍♂️


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[Bru-tom]

Let me repost yesterday’s events...

Changed to velocity stacks to kill any concerns with my custom intake (still need to post pics for those wondering what they look like)



And I do see some fuel in the overflow pipes... could it not be from knee scraping hard cornering etc?

Replaced plugs with new, room a drive to a mates place about 5km away with some stop and go traffic... bike started to do the same burble and spluttering towards the end of my ride, throttle response seemed better and at each stop I would normally have to “clear” the engine of an over rich mixture that would normally bellow black smoke out of the zhorst, which this continued to do....

Removed plugs...1,3 and 4:



And number 2🤷🏻‍♂️🤦‍♂️



When I removed the old plugs, they were all sooty and exactly the same as 1,3 & 4☝️

Where the heck does #2 come from now🤷🏻‍♂️

So yes, off with the carbs, again! I really was hoping that pods would have sorted this rich issue out. I am a little fed up now. But I must push on☝️


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[Deltarider]

Could you post a pic of your floatvalve needles?

[Bru-tom]

I will as soon as I remove the carbs from the bike tomorrow

Here is a video I snapped from the carb intake:

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It looks like a lot of fuel going in there

[BRG-BIRD]

I'm too lazy to reread all the posts, have you checked your emulsion tubes and slide needles for wear?

[HondaMan]

These carbs have a history of leaking fuel past the tiny O-rings that hold in the mainjet and pilot jet. Today's carb kits often sell a too-thin O-ring for those jets, too. They should be 3.9x1.2mm size, not easy to find. This will let almost as much extra fuel thru the jets as the amount of fuel they are supposed to deliver(!).

Also - have you changed the O-rings in the castings that hold the manifold to the head? These O-rings are the same size as the ones in the valve caps.

[Deltarider]

These carbs have a history of leaking fuel past the tiny O-rings that hold in the mainjet and pilot jet.

These tiny O-rings should be watched, the more if you have the bike hibernating with the floatbowls drained. The pilot jets in these carbs (069A) have no O-ring however.

[dave500]

the slow jet is screw in.

[dave500]

get a new 1mm drill bit,see how it fits in the main jet,you checked the plug caps yet?

[HondaMan]

Oh, yeah, sorry: I am thinking of the CB500/350 carbs with their push-in jets! 
The other part about the manifolds is still valid: I fixed [yet another] 550 last summer with black plugs by just changing the O-rings at the head.