cb550K3 carbs

[nairb]

So.... a part of the resurrection of my K3 was the refurb of the carbs.They are the originals.  So I took them mostly apart and cleaned up.  Then back together.  I made a jig to hold them and did a static fuel test........ They flooded.

Anyway after a bit of effort and re-setting the carbs up they would sit on the end of the fuel line from the tank and not flood or leak.  Which was all very pleasing.

So I put them on the bike and connected up the cables and air box.  It initially ran ok, no flooding but the idle and balance was a bit off.

Some 10 days later I get around to checking for air leaks on the carb rubbers etc.  Except now the carbs flood again.  Well one of them is - the lhs one.  Which is a pain.

My question is..... These are the old original carb floats.  Do they fail with age??.  I am thinking that they have sat there for nearly 2 weeks fueled up.  Do they go porous with age and now dont "float" as well when left in fuel.

I think its the last issue to fix before going for the mot. Its a long time since its been on the road so its still not registered as 'historic'

Ta
Nairb

[Bryanj]

No they dont its just pd carbs are a pain in the wottsit

[JezzaPeach]

With the 500/4 I can get the float bowls off using a mini ratchet with a JIS or Philips screwdriver tip.
If you can do that it might be worth checking the float has no fuel in it and if not, using a carb kit brush to give the float valve hole a good scrub. Maybe leave some vinegar in it to dissolve possible traces of oxide type deposits.

[Bryanj]

2 most common things on pd carbs are
1 pilot jets/pathways blocked, the jets are push in but will come out
2 pilot screws with missing tiny washers and O rings along with people who tighten them in too much and deform or break the tip

[michtag]

2 most common things on pd carbs are
1 pilot jets/pathways blocked, the jets are push in but will come out
2 pilot screws with missing tiny washers and O rings along with people who tighten them in too much and deform or break the tip

Speaking of o-rings, can anyone tell me their dimension? I'd like to have a few spare ones and don't really want to buy a full carb kit.
Also, would a broken/missing o-ring cause erratic idling?
cheers

[nairb]

Well I finally bought myself a mini ratchet and found I could get the outside float bowls off.  In the end I took the whole set of carbs off again.  Did my best to check the float hight and clean the float valve hole.  Rechecked the pilot jets were clear.  Put all back together and did a static fuel test - sitting under the fuel tank for hours.  No leaks.
 
So put the carbs back on the bike... Tank on - no leaks.  Bike started and did run better but still needs carbs setting up better.

Then the rh carb starts dripping.... and only stops with the tank fuel tap set to off.  No amount of "tapping" the carb would stop it dripping either.

These carbs really are a pain..... Other than that this old 550K3 is almost ready for its mot, then get it changed to "historic vehicle"

[Nurse Julie]

You don't need an MOT to register it as Historic, its not needed for the paperwork process, nor is insurance unless you live in Northern Ireland . Then when it's registered as Historic, you still don't need an MOT, it is personal choice whether you do or not. Can't help you with the incontinent carb though 😢😢😢

[Bryanj]

Yes a broken/missing O ring will cause problems, there is a newish post on the US site where somebody is fitting new adjuster screws and i asked nicely if he would measure the O rings before fitting

[nairb]

You don't need an MOT to register it as Historic,

Yup thats true.....but the post office says it must be on a SORN to be able to change its historic status at tax time.  Well this old 550k3 was on the road some 26/27 year ago and the sorn thing dident exist then.  So its in limbo.  No good phoning the dvla to have it put on a sorn either.  No sir we cannot do that. 

So the plan is :- to tax it for 6 months at the post office, then sorn it before the start of the next month.  Then go back to the post office and change its status to "historic".  It will cost one month of tax.

Its best to check with the insurance company to see what their attitude to NO mot is.  I always tend to have an mot. 
Anyway........ back to these dripping carbs.   I should have taken the floats off and put them in a large jar of petrol and see if they still "float" after a couple of hours.

[Nurse Julie]

All insurance companies are fine with the no MOT law on Historic, as long as the bike is maintained to a safe and roadworthy condition at all times. I still have all my Historics MOT'd, but that's because I like collecting pieces of paper for the bikes history file 😁😁😁

[paul G]

All insurance companies are fine with the no MOT law on Historic, as long as the bike is maintained to a safe and roadworthy condition at all times. I still have all my Historics MOT'd, but that's because I like collecting pieces of paper for the bikes history file 😁😁😁

I have always done mine at least once to prove after the initial restoration it was road worthy.

[nairb]

All insurance companies are fine with the no MOT law on Historic, as long as the bike is maintained to a safe and roadworthy condition at all times.

Oh yes they comply to the law.  I asked my insurance (pj) what they thought of the new(ish) mot rules and they replied that in the event of a claim they would "go thru the bike" checking for defects. 

So I chose to have an mot done.  Especially after a complete rebuild.  Apparently bikes with an mot history fetch better money at auction.... So they say.  It must help in the selling anyway.

I think it was an error to remove the need for an mot on older vehicles anyway.  Once every 2 years would be better.

[Bryanj]

The tiny O ring on the mixture screw is 3mm bore by 1mm cross section as measured by a UK member on the US site

[nairb]

I managed to buy a pack of 5 of these small o-rings for 1.69 off ebay.  Hopefully they will be ok.  Not a massive loss if not!.  They arrive next week.