Too rich!

[1mustard]

Hi, just some quick advice needed, my traveller is running too rich, i can only get it down to 7.5%, its a carb fault, standard 1098cc, what do these suffer with?, i have gone as far as i can on the adjustment and it won't go any lower.
cheers

[minor65]

Just checking you are turning the adjustment screw the right way. Down for rich, up for weak.

[1mustard]

yes mate, when you richen it up it goes off the scale like any car will. Won't go leaner than 7.5%, carb fault just need a few maybes on what may cause this.

[Neil MG]

.......just need a few maybes on what may cause this.

Worn or damaged needle/jet
Float chamber fuel level too high
Incorrect needle fitted
Needle fitted incorrectly (too far into piston)
Stuck jet

[MarkyB]

Worn jet and needle would be my guess, if the jet hasn't been centred properly this will happen.
If it is centred properly little or no wear takes place.

[1mustard]

thanks i will have a look asap, cheers

[bmcecosse]

The idle mixture is not important - what colour are the plugs after a good hard run?

[1mustard]

black as its running too rich.

[bmcecosse]

Hmm - I suspect needle possibly not fitted flush in the piston then. Is the piston free to rise and fall full stroke ?

[mike.perry]

I had an old carb which was running too rich, worn jet, I had to wind the mixture nut fully up. A temporary cure was to lower the needle shoulder below the face of the piston and re adjust

[1mustard]

thanks for all the good advice, i will crack on asap.
cheers again

[bmcecosse]

Within reason you can drop the needle - but not so much that it stops the piston getting right down on the bridge...... Leaky float valve is the likely cause - causes flooding when idling, but the fuel is of course used up when running. Test it by switching on - and NOT starting the engine - does the pump keep ticking??

[1mustard]

the pump only ticks once or twice on start up, i am going to have to have a good look inside the carb.
may be worth seeing if i can find a secondhand one through the club.
cheers

[1mustard]

Hello all, ok so today i stripped the carb, give it the once over couldn't see anything obvious, cleaned it all out etc, centred the needle etc, running richer now! won't go under 10% on idle, it stinks! when you rev it, it comes right down low, i am thinking new jet, float, float valve, needle, and give it a go again, hopefully it will cure it, depending on cost or a secondhand carb maybe the way forward, i checked the float height seems fine, i may just alter it abit out of interest and see what happens, the jet did have some scratch/marks on the side of it so maybe that would be a good thing to change first.
cheers

[MarkyB]

Scratches inside the jet sounds a bit desperate, wear that you can barely see will affect the mixture.
As the float and float valve are working I'd leave them alone.

[bmcecosse]

Almost certainly the float valve........

[1mustard]

I changed the float and needle valve because it was cracked but its still the same, i am going to change the jet, looking on ESM, do i just need the jet? or is there any washers/fitting that are worth doing while i am there?

[bmcecosse]

" because it was cracked " What was cracked? It won't be the jet....

[Neil MG]

If the scratches on the jet are on the inside then as MarkyB says ("a bit desperate") that's your problem and you probably need a needle too as that's most likely what made the scratches. If the scratches are on the outside of the jet, then that could only cause rich running if they prevented the jet from returning all the way.

[1mustard]

All sorted fitted a new jet and needle yesterday and shes ticking over sweet as a nut on about 3% job done! thank goodness for that it was so rich it was starting on 3 cylinders without the choke!!!! as for the cracks they are in the plastic float thats why i at first changed it but it didn't cure the problem.
Thanks for the good advice.