SU Carb prob!

[candy]

I took my carb apart (803cc) and now the piston wont raise more than a centimetre but when i remove the spring it raises all the way with no catching. I cant see how i can put the spring in any other way. I am sure it was raising all the way befor i got my hands on it as i was running the engine after replacing hoses. And where do you find what version of SU it is . I was expecting HS1 to be stamped on it but only to find ambiguous numbers stamped here and there. The neddle and dashpot damper are not bent. 1956 series 2[img:f42ea5e3f6]http://mmoc.org.uk/mbimage.php?src=1214423479_8323[/img:f42ea5e3f6]

[10852sm]

Hi,

Sorry I cannot help with the spring but I can tell you that you have an H1 or H2 carb, not an HSxx carb, H1 and 2 carbs have a central threaded bar through the float chamber and use a float with a hole through the middle and a central nut to hold the top on, HS carbs have three small screws which hold the top on.

I can also tell you that not all H2 carbs have the same diameter float chamber, some use a 1 1/2 dia float and some use a 1 15/16 dia float.

Hope this is a little help,

Steve

[youngun]

I have a spare 803 H1 carb if you need it!

[8009STEVE]

Stupid comment! I thought the 803 is a sidevalve. The picture shows what looks like a rocker cover. Does the 803 card work OK on a 948/1098?

[Welung666]

The 803 is the first A series, the sidevalve was a 918cc.

[8009STEVE]

I told you is was a stupid comment.

[Alec]

Hello Candy,

it is difficult to assemble the piston dashpot assembly incorrectly, I would remove it again, and see that the piston (with the spring in place) will move smoothly up and down the dashpot. If that is OK, then I'm guessing that you somehow got the dashpot canted on the body. Try again, as I said it is virtually fool proof.
The usual S.U. identification is a small aluminium tag, starting with the letter A normally like AUD xxxx

Alec

[polo2k]

if it sticks then leave the surface with a little color to it, then put the piston in with no spring and turn it for a while (unless its really tight) Youll be able to see the scuff marks where its catching.
If its all the way round then theres is somthing REALLY wrong, if its localised then it should be rectifyable.

[candy]

That is just it , it moves down the bore of the dashpot cleanly untill the spring is fully compressed and it cant travel anymore but this distance is only just over a centimetre and therefore does not lift to even the halfway point of the throttle opening. YOUNGUN,can you not whip out your spare carb spring and measure the free length for me? I have just bought the car so have no history of the carb plus it came to me on the back of a transporter. The spring i have is 5 inches long uncompressed.

[Alec]

Hello Candy,

what is the compressed length? It should be less than the length from the base of the piston to the top of the guide tube. (Guessing wildly at about 3").
In other words if you put the spring into the piston it should push down below the top of the guide tube.

Alec

[candy]

The piston only travels 1 centimetre into the dash pot before the spring underneath is fully compressed which relates to not much throttle opening. The engine is ok to idle . YOUNGUN ,cant you whip
your spare H1 carb spring out and measure it,s free length for me? This car arrived on the back of a transporter so i have no carb history. The diameter of my spring is 23 millimeter and as such rests on the first lip down in the piston . If the spring was of a smaller diameter it would go all the way down to the bottom to the level of the needle. Any clues there?? P.S the lip is about 1 centermetre down on the inside of the piston.

[Alec]

Hello Candy,

it is the wrong spring then, it should go all the way to the bottom of the piston.
Try visiting the Burlen web site, http://www.burlen.co.uk

I just had a quick look myself, and found the list of spares for a 56 Minor, which does not list a spring. I have never come across an S.U. before without a spring but it would seem it shouldn't have one? Try running it without and see how it goes?

Alec

[Kevin]

I am sure it was raising all the way before i got my hands on it

That may be the problem, if you didnt check before maybe the problem has been there ever since you bought it.
Like Alec I looked at Burlens and it doesnt list a spring but there is a reference to one in the list of parts so maybe its not available or superceeded by another.
It does rather look like your one is incorrect even the internal diameter looks a little large it must be from a differrent carb, lets hope someone like youngun can check their own and give you correct dimensions, or it could be worth while giving Burlens a call.

[candy]

Just to prove it, i cut the spring in half and the piston raises right to the top
and the engine runs and revs . I downloaded a program called winSUv2.6
and it tells you what choice of needles and jets you have but does not tell the part numbers untill you fork out 9.99 but it told me that a red medium spring (from Burlings)would be the baby without forking out 9.99.so i think i,ll try that. YOUNGUN, i still might be after that carb you got if it goes pearshaped!

[Alec]

Hello Candy,

when I looked at the Haynes manual it lists a red spring for the HS type carburettor but no spring for the H type. Unfortunately the procedures page shows a picture with a spring but I guess that that could be a generic illustration they are using.
I would ring Burlens to be sure. Adding a spring if it is not required will richen the mixture during acceleration.

Alec