SU carby service

[littlejim]

While researching this I found a section on the forum dealing with the problem in 2009,with some good advice but I've lost the reference - apols to those who contributed.

One part said 'lift the damper* and it should slide back to its original position with a satisfying clunk'. (* it probably said dashpot)

I've stuck another low gravity day. Mine stay up where I push them to. They look black rather than silver as well.

As an aid to cleaning them out I'm using the following article:

www.sw-em.com/su_carbs.htm

Edited June 20, 2010 by littlejim

[ianhoward]

Littlejim

 

The link looks a good resource...

 

Here in Blighty there are 'Carb Cleaner' aerosols that bring up the carb components nice and shiny removing all the deposits (with rag or suchlike). I have used these to good effect to clean up both the inside of the dashpot and the pistons thus eliminating the sticking and achieving the satisfying 'clunk' as the piston falls to the bottom of its travel... I would expect that there would be something similar down under?

 

Brgds

Edited June 20, 2010 by ianhoward

[vivdownunder]

Hi Jim,

 

Whizz down to Supacheap and get a can of Nulon Throttle Body and Carby Cleaner.

 

You usually fine sooty deposits on the aircleaner side of the damper, and inside the carby body around the butterflies.

 

Scrub with a toothbrush if necessary. (Best not to return it to the bathroom)

 

Check carefully that the circular lip where the dashpot fits down onto the body is spotless.

 

Tighten the three screws around the dashpot evenly, or they can pull it to one side.

 

Without the needles, test that the dampers now drop feely.

 

Then you have a benchmark for when you fit the needles and centre the jets, so the dampers again drop cleanly with a metallic clunk.

 

Regards,

 

Viv.

[littlejim]

Thanks Ian and Viv,

I've been at work with the carby cleaner. The rear one worked smoothly straight away but the front one was a bit recalcitrant, wanting to defy gravity. I redid it and did the inside of the carby body, and after eleventy twelve pushes up and down it gave up and behaved.

The next few minutes were rather interesting and comical to those who, unlike me know what they are doing. I should have the heading "an interesting day at the office".

 

With the choke disconnected I had to put duct tape over the carby inlet to get it started (short arms) - after the tape came off it settled down to a 4500 RPM idle! At first I couldn't believe it would go so fast with so little air able to get past the bottom of the dashpot/piston.

After playing round with the front shaft that the choke goes on, plus more carby cleaner on that, it came back to something a bit more like normal. While watching the temp gauge come up I decided the smoke from the painted exhaust pipe wasn't blowing the way I expected. A bit of paper confirmed that it was sucking instead of blowing despite my following the cheat sheet that came with the electric fan.

By then the Canberra temperature had dropped to below my accepted minimum so I pushed it back in the garage ready for a repechage tomorrow after the sun gets up a bit. Think I'll reconnect the choke until it warms up to operating temp.

As one of our UK friends has pointed out the Workshop manual doesn't cover the HS6 which makes it more challenging for mugs like me. Luckily Google finds some good articles that help, here's the latest one http://www.sucarb.co.uk/TechnicalDetail.aspx?id=81.

I'd like to see one that explains,for the ignorant, what the low speed setup is doing, especially as it seems to be operating mainly on the rear carby.

PPS the electric water pump worked like a charm gurgling away and remaining on for a while after I switched off. It could be running backwards too but I don't care, as long as it is running.

I'll get out of your way now.

Edited June 21, 2010 by littlejim

[littlejim]

Here is another reference for carby tuning that is easy to follow and well set out.

http://www.nicoclub.com/archives/2-write-ups-on-tuning-su-carbs.html

Edited June 21, 2010 by littlejim