CB550 K3 First thoughts - First Ride - Carb Issue?

[hunterso]

Hi all

It seems I have a little problem with my bike.
Please bear with me and I will try to describe exactly what’s happening.

I bought the bike only a couple of weeks ago after a 15 year lay off from 2 wheels.
It’s a 79 CB550K3 that’s had the café treatment, so the airbox has been removed and its running k&n style filters and a 4 into 1 pipe. Tank and seat unit, clip-ons and rear sets complete the look.

I blatantly ignored all questions from my family asking if i would be alright on that "with my back".






On my first available weekend i proudly rolled the bike out of the garage to start it up and listen to the beast.
Petrol - check
Neutral gear - check
Kill button to run - check
Contact!

Several presses on the starter and several almost but not quites, i sat puzzled on the rock hard pad that sits between the tank and tailpiece

Bugger!

I tried 2 or 3 more times on the starter and then decided to give it a little bit of choke.

My wife alerted me to petrol peeing from the carb overflow pipes so I turned the petrol off and left it a couple of minutes.

Bugger!

I tried again without any choke this time and eventually it started after 5 or 6 more goes.

Not a great start as I was expecting a short stab on the button and the sound of a beast roaring into life. 

The reality was a little way from that. There was a some smoke but this soon cleared along with my embarrassment of Mrs H rolling her eyes at my last grasp of freedom slowly fading away. 
Anyway the bike was idling and revving nicely – sounded great in fact and very responsive.


I didn’t get to ride it that day due to not having sorted my insurance 

Anyway curious about the starting issue I decided to pull the plugs (NGK D7EA) and found cylinder 4 was a little black (sooty)

I cleaned the plugs and put the bike away after the rain set in for the afternoon

Well with work and weather other things getting in the way it was a week later that I decided to take it for its first run out
Again, it wouldn't fire straight away but after 5 or 6 attempts using no choke it started up. I had to fiddle with the idle but after a couple of minutes I was able to get it nice and low and it revved cleanly.

So I took it out for the first time. I took it easy at first just to get used to her - she felt good.

I was enjoying my racer - Well apart from the ache in my wrists and my back - but we wont mention that.

I was just pootling around and after about 7 or 8 miles decided to stop and just check if everything was ok.
All seemed well apart from a faint whisp of smoke which seemed to be coming from the pod filter on the cylinder head. I understand this would normally be vented back into the airbox but as my bike is running k&n’s (or similar) the airbox is no longer there.

I also noticed a little weep of oil on the cylinder head too and could see it was coming from one of the valve adjustment caps
But the bike was sounding ok.

As I made my way back home I decided to give her a bit more gas to see how she went.
Riding a bit quicker now and letting the bike rev a little higher and again, all seemed well. I was soon getting into the rhythm of things.

When I got back into town I was riding slowly in traffic and noticed smoke was coming from the exhaust when idling, not a lot, but it was noticeable.

When I got back home I let the bike cool off and again pulled the plugs

Number 4 cylinder was very black and sooty. The smoke being unburnt fuel I suspect.


I wont get chance to look at this until Saturday or Sunday but my initial thoughts are that the float level on carb 4 is either too high or is sticking.

Would this explain the petrol peeing out of the overflow when I first tried to start her up?
Not sure which carb it was coming from but I’m now suspecting it was no 4.

Would this cause bad starting?

What could be the reason behind the smoke after more spirited riding?
Carb needle position?

I am going to check the sparks are ok at the weekend and have a manual on order – don’t really want touch the carbs until I have read the manual.

I have ordered new plugs and plug caps too, as the ones on the bike look original (NGK 5k resistor) and are obviously getting on a bit.

The weep of oil was caused by the valve caps not being tightened properly – 3 of them being only finger tight 

Anyway thanks for staying with me if you read it all.
Sorry for such a long first post but would really appreciate your thoughts and input.


Cheers

Darran

[Johnwebley]

my first thought,

 as the carb leaked initially,was it the No 4 carb?

maybe drop the floatbowl,and clean the float needle valve,

 also fit a breather tube to vent the gases behind the engine

[hunterso]

Hi John

Can that be done with the carbs in situ or do they need to be pulled?

[hairygit]

Hi there, and welcome Theoretically you could do the float valve with the carbs in situ, but as you don't have the standard airbox fitted, getting the carbs off is fairly easy, and much easier to work on upside down. But, before pulling the carbs of, remove the overflow pipes, then turn the fuel on, to make 100% sure it is No4 that is leaking . Aside from that, the starting problem is possibly caused by modern fuels, lots of ethanol and other nasties in it, some of the volatile components seem to evaporate quite quickly, leaving very poor quality/ low octane stuff remaining in the carbs, which can make it a pig to start. It seems quite a common problem on older bikes, as many posts on here will testify, I have never personally experienced this situation as I normally use the bike every day, but some guys on here have problems starting after not using a bike for just a week One more thing, if your bike is a K3, they were jetted very weak by Honda for emmissions and economy reasons, so don't be surprised if it needs full choke to start a cold engine!  

[deltarider]

I wouldn't open anything yet. Is #4 still peeing, then tap the float bowl with the stub end of a screwdriver. Maybe the needle frees. How old is the gas? After sitting for such a long time an additive like Seafoam, Forté, Tunap or other wouldn't hurt. Great stuf to 'lube' floatneedles and the like. I'd say almost mandatory.

[LesterPiglet]

My first thought is, isn't it strange that after one week without the engine running, it starts (with difficulty) without the choke?
 

[hunterso]

My first thought is, isn't it strange that after one week without the engine running, it starts (with difficulty) without the choke?
 

Hmmm I thought that too - but my garage is nice and warm if that would make any difference.

I am going to empty the fuel out of the tank and check the float in carb 4 tomorrow.
I'll clean and gap the plugs and see how (if) it starts with fresh fuel

[LesterPiglet]

Does your bike have the standard ignition?
It's just that I find my bike easy to start virtually chokeless but it has a Hondaman Ignition module, which I do know has been a huge improvement since I installed it.

[hunterso]

Yes, standard points etc.

Just had a look at the hondaman - looks good. Quite fancy one of them. 

[Johnwebley]

Yes, standard points etc.

Just had a look at the hondaman - looks good. Quite fancy one of them. 

I've used the basic Boyer since the late 70's,

simple and easy to fit and set up

[matthewmosse]

I ended up falling out with my k3 carb and engine combo with K&N filters on, the starting issues drove me nuts - worse in sub zero and snow so might not be such an issue for most users. Redex in the fuel inproves the overflow issue most of the time. tapping the float bowl with the handle of a srewdriver also often helps and can be quicker than pulling the carbs. As has been said, k3's are jetted to run on the lean side and give better economy but mine were never good at starting compared to my 500/4 which always fired up if you even looked at the starter button. I'd go with the easy carb fixes, take a ride then look at those plugs again. Always worth giving a service and new plugs and possibly plug caps - the plug caps have been the issue on about 7 breakdowns on my bikes (all 3 of the bikes in regular use have had the caps fail) in the last 5 years and I now carry wd40 in my toolkit to drive damp out and keep the bike running until nee plug caps arrive.

[hunterso]

Hi

Just thought i would add a little update about this.

I decided to pull the carbs in the end and have a look around.

Initial findings where

3 x 90 main jets and 1 x 95 
Different Float levels for each carb
Idle mixture screw tips - 2 ok, 1 bent and 1 that looked like it had been ground down from a larger screw
Found 2 of the mixture screw holes also each had one extra o-ring in there where some eejyt had failed to remove them before installing the  dodgy screws.

One of the float valves appears to be a little shorter than the others
One of the float hinges appears to be the wrong size as it is a really tight fit in the  mount - luckily managed to remove it without damage.

Good news is all the passages appear clear and unmarked

The slow jet has already been changed to a 42 but i also have 40's as spares

I have ordered new 110 and 115 mains as i am running pods and a 4-1 pipe
New float valves ordered too

I have also bought a complete new (used) set of carbs - so hopefully a will be able to make up one good set from the 2
and have plenty of spares for any future mishaps

I recall the chap i bought it from telling how he had spent hours setting up the carbs -

Yes it must have taken ages to bodge them so much - d**khead 

Not getting a lot of time to look at this but i'm in no rush and i'm enjoying the tinkering