tuneing the su carbs

[pinky]

Good evening gentleman

 

thank you stuart for you help today worked a treat

 

 

next prob, trying to tune the carbs,however when I wind the adjusted up trying to

make the mix lean it goes to the top and is still is running rich both carbs ,

 

any ideas

 

 

cheers pink

[AndyR100]

Choke not fully-off?

..... Andy

[pinky]

 

The chokes are hard up on the shoulder no upward movement

 

pink

[Lebro]

Lots of things to check: (on both carbs)

is the needle centred in the jet

is the needle at the correct height in the piston

is the piston moving freely in the cover

are the right springs fitted

is the correct needle type fitted, is the jet badly worn or oversize

 

Bob.

[RogerH]

...is there oil in the dash pots

 

 

Roger

[pinky]

 

 

oil in the dash pot

 

the carbs have worked well with good performance and economy (so should contain the right needle etc )

 

it started to smoke really bad, I discovered the chokes not retuning properly

I replaced the gaskets, choke now returns properly,

however it is still running rich, tightening the adjustment nut, compressing the spring should weaken the mixture (is that correct)

I believe there could be another problem, however the plugs are sooty black wich would suggest over fuelling

 

pink

[Don H.]

Float valve not sealing?

[Lebro]

+1 but if float valve not sealing you would expect to see fuel flooding out.

 

No oil in dashpot would make it leaner on acceleration, & no effect on cruising.

 

When you replaced the jet seals did you check that the jet was central to the needle.

to check - remove the springs from the cover, replace cover, wind jet adjustment fully up, lift the piston by hand, & let it drop - it should go down with a clunk. If not the jet is not centred, and is hitting one side of the needle, which can then not go fully down.

 

Bob.

Edited December 14, 2016 by Lebro

[vitessesteve]

 

You may find the "Tuning SU Carburetters" booklet useful I have a copy on my website at: http://vitessesteve.co.uk/Other-manuals

[BlueTR3A-5EKT]

 

You may find the "Tuning SU Carburetters" booklet useful I have a copy on my website at: http://vitessesteve.co.uk/Other-manuals

Fine and useful tech notes and info

Thank You

Peter W

[pinky]

Thank you gentleman for your help with this matter,

 

today I went out re centred the jet etc etc

started car run up lovely, smoked, then cleared, thought I cracked this

left it running, got it up to temperature then it smoked like a pig so I think I have got a blown head gasket,

presumably when hot the expansion allows the oil to flow into the barrel

did a compression test and the third plug hole from the front is down

 

unless any one has got a different idea on this problem

 

thanks pink

[vitessesteve]

If you think oil and water may be mixing due head gasket failure can you see any oil in the cooling system or water in the oil?

 

What colour is the smoke? Oil tends to blue hue. Unburnt fuel to be a black soot. Water may appear as white clouds.

[Lebro]

Before removing the head, try torqueing it down again.

Easy to do, & might just save a lot of work.

 

My '3 started playing up with regard to water temperature earlier this year. Turned out to be a slightly leaking head gasket - compression to water jacket.

totally cured (for now anyway) by re-torqueing head studs. I got quite a lot more on them such that my rocker clearances went -ve !

 

Head was last tightened by the Factory in circa 1968 when the engine was factory reconditioned.

 

Bob.

[pinky]

Before removing the head, try torqueing it down again.

Easy to do, & might just save a lot of work.

 

My '3 started playing up with regard to water temperature earlier this year. Turned out to be a slightly leaking head gasket - compression to water jacket.

totally cured (for now anyway) by re-torqueing head studs. I got quite a lot more on them such that my rocker clearances went -ve !

 

Head was last tightened by the Factory in circa 1968 when the engine was factory reconditioned.

 

Bob.[/qwuote]

 

good idea bob, I will try that

 

no oil, and water mix

oil is being burnt

I believe it is leaking carb side, centre,

[Richardtr3a]

I had a similar problem but not so bad.

 

After the MoT many years ago, I filled up with petrol ,from a small local garage in the Cotswolds, to help their sales.

 

The car immediately started knocking and I went back for a fuel additive. The knocking continued and the plugs were blacking up continuously

 

I had it tuned by Southern Carburettors who could not improve anything.

 

It took 700 miles and a trip to Classic Le Mans before the noise faded away. The mileage never went back to the previous high mpg and a number of experienced tuners have looked at it since then. I was always cleaning the plugs and kept the kit in the passenger footwell.

 

I want to enjoy the car next year so the carbs are going away on holiday after Christmas, for a full rebuild.

 

Good luck Richard &H.

Edited December 16, 2016 by Richardtr3a