SU Carb Emissions removal

[Shawn]

I have a 1-1/2 SU in good order, however it is the later emissions control type with the waxstat jet and poppet valve in the throttle butterfly.

This site offers a nifty way of removing the often faulty waxstat:
http://www.nireland.com/gd.triumph/waxstats.htm

I was wondering what peoples thoughts were on removing the poppet valve and filling the holes in the butterfly with solder. I'm pretty handy with a soldering iron, so I know I could do the work ok, and I think the butterfly would remain cool enough that the solder wouldn't melt and be sucked in to the engine.

Good or bad idea?

[Stig]

The esteemed Mr Vizard says it's a good idea, and that's good enough for me. The carb certainly won't get hot enough to melt solder unless the whole engine's on fire!

[picky]

Maybe keeping the poppet valve will restrict airflow and make the upgrade from 1 1/4" to 1 1/2" pointless, I would get rid of the poppet valve.

[Packedup]

Word of warning with the 2p trick - If the bottom retaining bit on the jet is corroded on you may well find something breaks trying to get it off, so make sure you have a spare!

Other than that it works very well, a bit of epoxy on the coins and little metal bit can help when trying to fit it all back together

You can simply solder up the poppet valve, although it will mean the valve itself is still restricting the airflow a bit. Might be worth just finding and fitting a plain butterfly really, even if you can't find a freebie s/h one they don't cost an awful lot new.

[bmcecosse]

Remove the valve and solder up the hole! Also remove the ends of the holding screws - although the difference is insignificant.

[Cam]

You could also 'knife-edge' the butterfly too and build up the 'step' in the jet bridge with epoxy resin if you fancied it. Also, you could thin the butterfly spindle down. I did all this to a carb once (HS4) and then ended up giving it away to a mate who needed a carb before I could use it!

[bmcecosse]

The bridge building bit is definitely NOT recommended for road cars. But yes I have knife-edged and thinned - and filed a big 'bell mouth' on the inlet flange to eliminate the vena contraca effect.

[Cam]

Well, I don't think any of it will make much practical difference really unless you need more flow than the carb can supply, in which case you really need a bigger carb!

If it's for a mildly tuned road car then I would not bother removing any of the carb bits, personally.

[Packedup]

I'd get rid of the waxstat if nothing else. The "interesting" effects they can create when playing up (or maybe when working normally, is there such a thing as a properly functional waxstat?) just isn't worth the hassle when it costs 2 pence UK money to remove it

[Shawn]

I'm only going to get rid of the poppet and waxstat. Did the poppet last night and it has soldered up and sanded beautifully. Will tackle the waxstat in the next few days, probably while listening to the Boxing Day test.