CB550K3 carb needles ???

[OZZYSBIKES]

HI,

I have a CB550K3 and it has never run well since the first day of ownership, it has always run very poor at low throttle openings so I have removed the bank of carbs to overhaul them,

On strip down I have found that the needles fitted in the carbs are 4mm shorter than the new ones provided in the service kits, this could explain the poor running at low throttle openings (some of the stuff that I have found engineering wise on the bike means anything is possible), I have also found blocked airways that could explain the poor running,

The carbs are the Keihin PD46A suffix PJ t

does anyone know which are the correct needles as it is not 100% certain by looking and measuring which ones it should be,

Any info / help much appreciated.

[Nurse Julie]

PD's are notoriously shite and always have been that's why most people bin them given an opportunity. No idea about needle length though but if your carbs have never been apart, or at least, had brass ware changed, I would suggest you have not got the correct replacement parts.

[SteveD CB500K0]

I think the general consensus on here is to save your time and money and get a set of carbs from an “F”.

Then spend your time and money setting them up.

I’ve had three K3s. None in the last 20 years though.
They were great in the 70s but I suspect they don’t like modern fuel very much.

Steve

Another vote on pictures please. You need five posts to attach pics, but I’m sure that won’t be an issue for long


Sent from my iPhone using Tapatalk

[OZZYSBIKES]

Thanks for that,

I agree with the fact that the PD carbs are shite but CR carbs are a tad pricey ! I am making the best of what is on it, do people put the earlier carbs on as a replacement ?

I have no idea what the previous owner has or hasn't done with the bike or any of the other owners so cannot be sure on whether the needles have ever been replaced, I guess no one has compared the PD needles with any others I.E. the ones from the previous type of carbs ?

If no real answer to the needle length relative to the type of carbs fitted I will measure carefully and use my judgement, it is looking like the short ones are correct for the PD carbs.

[OZZYSBIKES]

HI Steve,

Yes I agree about getting another set of carbs, I intend converting it to look like a F2 and fit a 650 cam plus possibly a big bore kit as I love the relaxed ride that you get with the bike (my son calls it the armchair) but it could do to be a bit more capable of motorway speed cruising, I already have a good four into one exhaust so the better carbs will fit in with my plans for this bike,

Cheers

[OZZYSBIKES]

Got the carbs back on the bike with the shorter needles fitted, it runs better than ever but that is only with it running in neutral, I will feel better when I can take it for a spin and test it under some load,

It appears that the new longer needles are the wrong ones for my 550K3 carbs.

[kevski]

I know the carbs can be a problem on these, but my 500k3 had them on and the only time i had running issues was when i had the bike serviced at a local dealership, it came back running terrible, i bought a Morgan carb-tune stripped, cleaned and set them up myself and never had any problems there after, but the bike was run everyday in all weathers, i think you have to keep them running all year as the modern fuels do no favours.

[matthewmosse]

When I had a cb550k3 as a daily use bike it didn't mind being left standing the 6 months between me buying it and passing my test, or the odd layover once I got a cb500/4 sidecar. I did appreciate the better fuel economy and the only running issues I had with the bike were attributable to the absolutely appalling engine condition. I did try switching some k3 carbs and engine to my 500/4 many years later, with k&n cone style filters and later the stock filter setup but by then something wasn't playing ball. Not sure if it was the same bank of carbs as I have a few sets kicking around. Depends what you want from the bike, I liked the extra mpg and tank range. I think I was still running the k3 though into the era of modern fuel.

[OZZYSBIKES]

Well I decided to get a holdall strapped to the bike so that I could do the food shopping on it, well ! I am delighted, it's running perfectly now, just need to make my mind up whether to fit modified CB750 pistons or buy the cruzin image big bore kit, I definitely want to give it a little bit more power and already have two CB650 camshaft, I am looking forward to rebuilding the engine ready for the late summer or autumn ride outs

[Richie 550/4]

Hi.

Sorry to break the subject matter.

Can you tell me where you are finding your serial numbers on your Kei Hin carbs please?

I am currently renovating my bank and the only number I can find is 069A

Everything I have read and heard you guys discussing are numbers with a letter prefix.

Any help greatly appreciated.

Richard

[Bryanj]

650 cams have different tach gear and clock

[mickwinf]

richie your number is correct for the earlier models, no letter, and actually are considered a better design than the PD type

[OZZYSBIKES]

richie your number is correct for the earlier models, no letter, and actually are considered a better design than the PD type

Hi Bryanj,

I actually have a complete CB650 engine which I bought second hand just for the camshaft and tacho drive, I then found another CB650 camshaft so all I need now is some way of matching the tachometer to the bike, I think that the best option for that is a speedo and tacho (spurious) from David silver that are for the 650, the clocks have a black background but I can live with that,

I have today bought the big bore kit so have most of what I need in place to make it a bit of a gentleman's express 550, I will probably gas flow the head myself with help and advice from a good friend who builds big air cooled four cylinder engines for various racers and has had 180 hp out of his engines so he certainly knows what he is doing !

[Nurse Julie]

Jeff. I have replied to your eBay enquiry via a PM on this forum 😁😁😁😁