Vit 6 cd150 carbs Random flooding

[zhcj]

anyone shed any light onto this problem i have on my 1965 vit 6.

purchased 2 supposedly overhauled CD 150 carbs although they were of a mk1 2 litre car. i was assured they were the same carbs they look identical to my original ones in every aspect . they are not the emission control later ones so i put them on with a friend.

i have replaced the main needles with correct vit 6 ones just to be sure as the 2 litre ones i was told were different . im told the jets are the same for both the vit 6 and 2 litre  cars

have replaced both float needle valves and also swoped over the floats from my original carbs,

i seem to get random flooding usually when it has been stood for a day or so overnight or just started up to move it out of the way quickly. then when i come to drive it a couple of days later after a mile or so  the carbs flood and fuel runs down from the air intake. it was mainly just the rear carb causing the problem but the front one also started to do it, when i  gave the front one a quick knock on the float chamber it seemed to be ok . other the the random flooding the car runs very well it does not flood all the time any suggestions would be welcome wish i had kept the original ones ones on

[glang]

well its got to be float/needle valve related. Either: dirt in the valves/some other problem with them so not sealing properly or floats not working/poorly adjusted.
I would revise the system again checking by blowing through the valves in situ that they seal when the floats are raised by hand as well as closely inspecting the floats for punctures, free movement and correct height setting.
Also you should look for any dirt in the bowls and in your fuel pump filter as an indication to the cleanliness of the fuel supply system.
Stick with it as it cant be anything too serious.....

[zhcj]

Thanks for your reply I was thinking maybe some rubber slithers with taking the pipes on and off the floats look ok there does not seem to be any fuel in them . I have not touched the hieght of the float it's exactly as it was . How do you mean blow in situ into the needle valve ? Do you mean with it in my hand . Could it be worth getting 2 new floats assuming they are available. ?

[glang]

well its a bit fiddly but you can remove the bowls off the bottom of the carbs and then blow into each carb by its fuel inlet (after removing the fuel pipe of course) then you raise the float up gently by hand until at the correct level it closes the needle valve and you can no longer blow air through. If you can continue to blow something is wrong.....
With the floats its unlikely that both have failed so I wouldnt be in a rush to replace them just yet. If the needle valves work correctly and at the right float level the next stage is probably to remove the carbs completely as its quite difficult to work on their underside in situ. Then closely inspect the floats for possible punctures shaking them to see if petrol has entered inside (the idea being that if it leaks it wont float and do its job).
As an aside I assume you havent got an electric fuel pump fitted which could be overpowering the needle valves?

[zhcj]

Hi thanks again no it's the original fuel pump could be as you say dirt has got in during the change over I will try the check on the needle valves as you suggest.

[zhcj]

If it is the height of the float that's wrong without taking the carbs off which I'm trying to avoid doing to measure does it sound from my description of it were to be the float that the float is sitting to high or to low when I replaced the needle valve I put back on the same size washer that was on originally the medium size one if the three which came in the pack

[thescrapman]

Did you fit new bowl gaskets? Or swap them over.

Not all gaskets are the same, and a couple of combinations cause the float to catch on the gasket.

[zhcj]

New ones but exactly the same as the ones I took of when I replaced the needle valves

[glang]

Quoted from zhcj

If it is the height of the float that's wrong without taking the carbs off which I'm trying to avoid doing to measure does it sound from my description of it were to be the float that the float is sitting to high or to low when I replaced the needle valve I put back on the same size washer that was on originally the medium size one if the three which came in the pack

Well the float would have to be sitting very high (ie the distance from the base of the carb to the bottom of the float would be much less than the 18mm that my manual quotes) so that the float is reaching the end of its travel before it has fully closed the needle valve. It also suggests that the different washers can be used to change the level so avoiding adjusting the floats themselves.
However I cant see the float adjustment being the problem as it usually only affects the fuel mixture and not cause overflowing. If the needle valve washers didnt seal for some reason or the floats were, as suggested, catching on something then you'd get it.....  

[zhcj]

thanks again i think ill inspect the float chamber on the front carb as thats only leaked the once for any sign of debris that may have caused the needle valve to stick

[zhcj]

as a matter for my interest you mention the float level affects the fuel mixture ?

in which way, if the float say sat to high or nearer to the bottom of the chamber so less than 18mm but not enough to cause the valve not to close fully would that make it to rich or weak?

[glang]

In this case the level in the chamber would be running higher so it would be easier for the venturi effect in the carb to suck the fuel from the jet hence you would have a richer mixture. How much this effect is I dont know but the level setting recommended by Triumph seems to be quite precise so I guess its important.

[glang]

Hey I found this on line which is interesting:

Air velocity past a pickup point in the venturi area causes a negative pressure in the fuel well. Atmospheric pressure in the bowl (the bowl is open to the atmosphere via the bowl vent) pushes fuel from the fuel well through the pickup into the venturi area. With the engine off, fuel in the fuel well will be at the same level as the fuel in the bowl. The level of fuel will alter the amount of negative pressure necessary to cause the fuel to flow.

A good general rule is that a 1/16 inch change in fuel level is approximately equivilent to one jet "size". This approximation is good to know when "dialing in" a different carburetor, as it allows the tuner to "try" a jet size without buying the jet. However, don't try dropping the fuel level by more than an 1/8. And this change should not be permanent, only for testing.

[zhcj]

thanks again ill let you know if any progress

[daver clasper]

Hi.

I had similar issues. on both carbs after fitting a set of second hand float valves.

They were sealing when I blowed through them, though pump pressure is a lot higher than this, so not a good test apparently.

I was advised to give the valve pins a light tap with a hammer as this can reseal them.

This worked. No problems since.

Cheers, Dave

[Pete Lewis]

And  to add  the 1600 does not have a piston spring but does have a thicker heavier diaphragm retaining ring   a spring will make it run rich across the range

this has all the  feelings of the dreaded rubber sliver syndrome, best to remove the needle valve and look  behind it,  while the pipes are off spurt some fuel into a jar , see what arrives  take care with refit or you make some more

make sure all the front face ports are not obstructed with gaskets or air box  fitting.

Some floats have two valve arms and the float can be fitted upside down with  ig effects on float operation even if the 18mm is set

pete

[daver clasper]

Also. Another time I fitted an air filter upside down, with the cut out bit a the bottom, so severely restricting air flow. Ran ok until hot then terrible with lots of flooding.

Regarding slivers. Smooth any bur off metal petrol pipe ends and I also smear a tiny bit of vaselene on to connection end to maybe prevent slicing into the rubber.

Cheers, Dave  

[zhcj]

thanks for reply's all very helpful

the float in the front carb turns out was leaking fuel into it even though it was working ok previously so ive replaced that with a spare i had and so far so good its all working.....i hope

[glang]

good news! Did you find anything wrong with the rear carb? It could have a leaking float considering its probably the same age as the faulty one or of course, as sod's law dictates, it could be something completely different.....

[zhcj]

no the rear one remains a mystery it leaked originally although supposedly overhauled so i replaced with a new float valve and the float from my original carb and it still flooded . neither float the original or mine was leaking. the only difference was the ear on the original float was slightly bent upwards towards the needle valve where the one i had on my original was flat. so i put the original one back in with the ear slightly bent guess that means it closes the valve sooner?

so far its been ok but im waiting for the flood again on the rear one or it could have been a rubber sliver thats cleared out itself when i took the bowl of.

one other question i notice on these carbs it does not need any choke at all to start it so i assume its running rich?
on inspecting the plugs they are black if its short town stop start journeys but they do grey up to the correct colour when its run without stop and start all the time .

[glang]

yes it must be rich as you should need choke to start. Really it sounds like it could do with a complete set up then you can be sure everythings good:

check/adjust engine valve clearances,
balance airflow through each carb,
set correct mixture and then tickover.

The last job can be done with a colourtune unit installed temporarily instead of a sparkplug or using the small plungers that your carbs should have. I use the second method but it does take a bit of practice. The idea is that with the engine running operating the plunger lifts the carb piston a fraction and this causes the revs to increase if rich, drop if weak and stay unchanged when correct.....

[zhcj]

thanks very much again  i thought that if the engine revs increased then quickly returned to normal when pressing the spring plunger up on the piston then that was correct.
thats what happens here the engine revs rise but quickly drop back when i press that plunger, they do not remain high which i allways thought was rich. ive got a colourtune also but rarely find that accurate. an old experienced now retired triumph mechanic always said to me you had to set them to run rich to allow for the lower octane fuel. when i last checked it it was doing 20 mpg round town  

[zhcj]

its certainly rich on short journeys i can see that by the plug colour but seems to be ok on a longer run judging by the plug colour anyway if thats anything to go by.
i guess i could always screw the mixture screw upwards half a turn on each carb see if that weakens it of maybe

[glang]

what youve described from the plunger operation is a rich mixture. Its the engines immediate reaction on pressing it that shows whats going on and when correctly set there should be no change. I give the plungers a jab when I do it cos if you hold em for longer then this will have an effect on the running and can make you think the adjustment is wrong.
You can try a tweak of the screws as I dont think your mixture is far wrong but the further you go doing it 'blind' the more chance of error as the carbs might each be different....
Finally I use an octane/lead additive (Millers VSP) in my Vitesse which allows me to run standard ignition timing and a pretty lean mixture (36mpg on long runs) without excessive pinking or run on.

[daver clasper]

Hi

I have the same thing. Starts sometimes without choke on warmer mornings, runs rich in the city (though have heard this is normal), and correct colour when cruising.

Seems to be doing around 23 mpg in city, 34 mpg when cruising (with overdrive).

I wondered if my needles were more worn at the lower ends causing this, but I guess yours are new.

Cheers, Dave