Topic: Honda cb550 f2 spark plug different readings

[adrian]

First post.
So I hope this is the correct place to post this question.
The spark plugs are showing the bike is running rich 1 through 3 cylinders and the 4th looks lean to my eyes. I;ve synced carbs, checked timing  and valve clearances . I don't have air filters on it. Also the pipes 4 into i no muffler (spark plugs are the same as when I had a muffler and air fliters.
Why the different spark plug? one lean dosent make sense to me. The jetting is stock for a 1977 cb550 f2.  I've taken the carbs off for cleaning and changed grommets/ gaskets. I'll have to re jet but rich is better then lean.
Anyone have a parts dealer in Australia for this make and model?
Cheers 

[adrian]

This is my ride

[adrian]

and another pic

[Duanob]

When was the last time you opened the carbs up and cleaned them? With no air filter you may have to do that quite often. My air filter gets dirty pretty fast if I ride a lot. I would'nt want to think of all that crud getting inside my carbs.

[TwoTired]

I don't have air filters on it.

Why do you hate your engine?

Why the different spark plug? one lean dosent make sense to me.

One carb is different inside than the others.

The jetting is stock for a 1977 cb550 f2. 

What is it you consider stock.  Have you verified stamped numbers match the actual dimensions?

I've taken the carbs off for cleaning and changed grommets/ gaskets.

Did you clean the emulsion tubes?

Have you vacuum synchronized the carbs?

I'll have to re jet but rich is better then lean.

Only in one aspect.
Too rich contaminates oil more rapidly.
Too rich washes cylinder walls of oil, accelerating wear.  (But, so does blasting the cylinder walls with dirt in the air supply.)
Too rich promotes air pollution.
Too rich wastes gas.

What is most curious is that the stock carbs were set up for minimum fuel delivery with the stock air filter and higher back pressure exhaust.
They should all now be stupid lean with no air filter and open exhaust without internal changes.

Are those carbs stamped 069a?

Cheers,

[adrian]

 Ha Ha hA I don't hate my engine I was seeing the difference. I ride with people that never use air filters their bikes are all good . I cleaned the carbs recently and they where squeaky clean after weeks of no air filters. All the carbs have the same jetting. I'll check the stamp numbers and get back to you on that.  emulsion tubes cleaned . Yes, I vacuumed synchronised the carbs. It should be stupidly lean and I had taken off the are filters to test that and the muffler.  I'll chuck the air filters on to see the difference.   
Rides fine, I had the idle a little high and it was not too smooth at the lights but i rectified that and all good. Changed oil forgot to smell for petrol so next change i'll do that. But I;m not riding until I get this sorted. I have an XS650 which is awesome too.
Are those carbs stamped 069a? I'll check that.

THanks for the replies

[TwoTired]

I ride with people that never use air filters their bikes are all good .

...so far.   
But yes, they will run until they break or wear out the cylinder and piston rings.  Those are easy to get and install, right?
Didn't you ever wonder why every engine manufacturer supplies an air filter with the engine?
Don't you have insects where you live/ride?  Stones? rocks? sand?

I cleaned the carbs recently and they where squeaky clean after weeks of no air filters. All the carbs have the same jetting.

Ok, you might check that all the floats are adjusted to the same height.  That all the float valve needle spring pins have the same strength.  And, that the actual fuel level is the same among all four carbs when filled.

Seems straight forward to me that there is something different among carbs.

Cheers,

[LesterPiglet]

It seems to me running without filtration is a no-no. I live in a damp atmosphere which keeps most 5hit stuck to the ground. I would never dream of driving without filters in a dry climate.

I have standard filtration.

[adrian]

Ok Ok point made and taken, Air filters are back on the bike ( only off to see if it would lean it up a bit). So back to the beginning why the lean plug? I'll check the float levels  and look at replacement floats and seats.
Thanks again
i'll check all the info given out