First Start Highs and Low!

[Neilw]

It’s well known if you leave the ignition on and the coils energised they are prone to burning out Ted. It’s not common as it requires some time to happen but it does happen now and then. Other than the leads they are almost indestructible.

Sadly, my leads and caps are all fine.

[Neilw]

An Update - You have to laugh!

So, I ordered new coils, and while waiting for them, i decided to remove the carbs again and go through everything one more time, albeit a bit slower.

I rechecked the float heights and depending on how you had the bowls tilted, they were either spot on or miles out! So I redid them and stuck them back on the bike, only to see No 2 leaking!

You live and learn, so i took them off again and went through the process again - however this time, I stuck a bit of clear tube in the drain holes of 3 and 4 before filling with petrol on the bench. One overflowed and the other was not filling up. So off with the bowls again and repeat the process, which i must of done 4 or 5 times until both bowls were filling to just below where the bowl meets the main body. I repeated the process for 1&2 and eventually got those the same. This process seems to be an art; I even made a float height template using an old credit card, which saved me loads of measuring time.

While I had the carbs off, I also checked all the slider needles; they had the circlip on pos 2, and I cleaned and blew through everything in sight. Also did Bryans bench sync again.

Carbs back on.

New coils arrived a few days later; I decided to test them with my multimeter, only to discover that they also had the same readings as my originals.  Turns out I don't know how to use a multimeter correctly, i had it on the wrong setting. Now I'm getting the correct reading on the secondary, so I went back to my original coils and lo and behold they are OK! I double checked the caps and ht leads and they are within spec.

Put them back on the bike, and start the old girl up. With the chock on, it didn't want to know, but as soon as i took it off the bike, it started and, at a sensible rev limit, no racing to 6000rpm. It was running a bit lumpy, which I put down to needing to go through the tuning process, but also discovered No. 4 was not firing - which is where I started all this!

Turns out the spark plug is dead! I've ordered 4 new ones.

Hopefully, with the new plugs installed, I can start the tuning process with a bit more confidence!

The new coils are being returned.

[McCabe-Thiele (Ted)]

An Update

While I had the carbs off, I also checked all the slider needles; they had the circlip on pos 2,

When you say position 2, is that from the top of the needle or from the bottom?

The 550 might be different, my 500 has 5 positions, I used position 3.

[Neilw]

An Update

While I had the carbs off, I also checked all the slider needles; they had the circlip on pos 2,

When you say position 2, is that from the top of the needle or from the bottom?

The 550 might be different, my 500 has 5 positions, I used position 3.

Mine also has 5 positions, it's 2 from the top, which the book says is the default position.

[McCabe-Thiele (Ted)]

I thought that for a UK bike, the middle position was correct, US  models were one ring position richer.

[Neilw]

I thought that for a UK bike, the middle position was correct, US  models were one ring position richer.

For  my model 1978 CB550 F2 on 069A carbs it's position 2.

I fitted the new plugs and the Bike starts and runs on all 4 cylinders now. I reduced the throttle screw and actually got it ticking over, so now i can go through the tuning process and see if i can get it running smoothly! Quite excited for once !

[K2-K6]

If you've got the carb bench sync routine completed to good level, as Bryan's posted routine, then there's no need to change that in "tuning" operation subsequently.

Its easily good enough, when done competently, to give perfect results. Changing it with the use of gauges brings the risk of leading you the wrong way IF there's other elements that affect vacuum accuracy.

Broadly speaking EVERYTHING else in setup needs to be verified and accounted for BEFORE even considering using gauges on it.

It helps with all the other settings to know that the sync is competent in finding other faults.

[McCabe-Thiele (Ted)]

I do find it confusing that the 500 & 550 are grouped together here.
My 500 needle was in the middle when dismantled so that's how it went back.

[K2-K6]

I do find it confusing that the 500 & 550 are grouped together here.
My 500 needle was in the middle when dismantled so that's how it went back.

It shouldn't make a big and fundamental difference Ted, it's really fine tuning in those steps to set the needle and won't as such give the fault experienced here.

All it does is move the mid range throttle fuelling up or down a little to tweak response or cope with plugs just a little too dark etc.

Clear fundamental issues in mixture will come from wrong spec or worn components to give the bigger steps of error seen so far.