Carburretter check and adjustment

[Adrian]

Hello all

 

As a double check for those in the know and those who would like to know I'm going to attempt to put together a quick step by step guide on checking and adjusting CD 150 carbs as per Pete's great instruction during the tutorial day. Just so you know - I've never touched a carb before and am not a mechanic so if anyone wants to refine this please feel free.

1. Visual Needle adjustment. The basic setting is the washer on the needle at the base of the float should be more or less be flush with the base of the float. This is adjusted by as long allen key or special car adjuster tool (the adjuster has a centralisation sleeve to prevent diaphragm damage). Please note, float chamber disassembly does not result in parts springing out and getting lost although caution should be used to prevent threading of the screws / sockets during re-assembly. 

I think this is sitting a little too far out (correct?)

 Check the diaphragm isn't distorted. If it is soak in petrol and it should reform to its original shape.

Don't forget during re-assembly to make sure the tab on the underside of the diaphragm is located in the corresponding 'socket' in the carb body.

Right hand side of the photo. Obviously carefully re-insert the needle into the slot as seen in the photo.

2. Temperature compensators. As I recall these are to facilitate consistency between cold and warm starting. Not all carbs have them. If you do they are easily recognised....The yellow plastic covers. If you remove those bigger screws adjacent to the plastic cover you get the following

Note the two rubber washers. Basically it is a bimetallic strip which operates the cone in the middle of the above picture to adjust (I think air into the carb)? With the washer off it should offer slight resistance when pressed, if no resistance adjust the nut on the inside until you feel the slight resistance as follows. The nut should move freely with pliers.  

All of the temperature compensator adjustment is totally irrelevant if the air intake on the carb is covered by a wrongly / deliberately placed gasket. They can operate without them and it was apparently a common feature to blank them.

You can see the cut out for the intake in the above although ironically the intake for the other carb was blanked by a reversed gasket - perhaps that is why it never started particularly well.

3. Choke. Pete said to make sure there was no corrosion on the plates, if there was, clean them. Fortunately spotless.

Although may have to get a gasket as the one on there seems a bit rough.

4. Finally - balancing (if that is the right term) - visual

The picture of the carbs above shows a screw on the top right of each carb. This adjusts the opening of the baffles? (the brass thing!) I just adjusted them visually until they both operated the same.

Then it is a good clean of the outside with 00 steel wool and carb cleaner.

Hope I've remembered it correctly Pete!

Adrian

 

[Pete Lewis]

Adrian,  spot on,  you can remove the (I thinks) you are correct

One point the temp compensators are there to bleed air past the throttle plates and thisnweakens mixture and raises the idle a little 

When under bonnet temperatures get too hot for normal settings  its an emmision gimickmfrom the 70s .

If they are open for normal temperatures you dont set the mixture correctly, hence the simple view is they should be best closed 

There are detailed how to set them up which is beyond most diy tinkering so Closed is the best option

Pete

 

[dougbgt6]

 Adrian, good job! Although, there's nothing wrong with that gasket! Bit of Hematite, it'll be fine. 

An additional thing you could add is taking the needles out to the replace the "O" rings that stop the dashpot oil disappearing. There is a spider washer that holds everything in and is liable to ping off and disappear.  I lost both mine! Double T shirt. 

Buckeye triumphs site show a detailed overhaul of TR6 Stromberg 175 CDs which are similar, they show the needle, spider, etc in the overhaul section. But it's high time we had a specific 150 version. Well done.

http://www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm

[Colin Lindsay]

Excellent job, pin this as a sticky thread... although I hope it's just the angle, the needle in the first pic looks to be at an angle compared to the piston... :0

 

Just about to start on a Stromberg for a 1200, it's been years so wish me luck.

[Pete Lewis]

yes colin the angle is a biased needle they are sprung  towards the engine (so are some SU) so the fuel gets sucked from around the needle not from the back of it,  for better atomisation 

only found on top adjuster CDSE  not on CD or CDS  they should be a fixed needle,  nothing to stop you swapping all the bits over if you feel adventurous.

Pete

[Colin Lindsay]

Too modern for me, those fancy later carbs... but nice to know there's nothing wrong with the eyesight!

[Pete Lewis]

Ah  what !  speak up 

go to spec savers they make em look  upright

Pete