rebuilding carbs

[ST1100]

This is exactly the same as mine 1970s Emcomat 7 with milling head. It was made in Austria...

Indeed 

We had an Emco 8 in the company I spent my apprenticeship (electromechanics and mechanical engineering) at, very versatile machine... (back in the day we still repaired things instead of replacing...)

Got me a small Erba Compact 300 for the bike shed, perfect for small items and still light enough to carry and store away in the shelf when not in use.
Don't need it often, but when, you're in dire need to have that little lathe at hand...

[exvalvesetdabbler]

My biggest regret was not buying the milling head to go with my little lathe.  It's been worked hard over the last 40 years and has a few faults now. Originally sold as a model makers lathe.  It's earned its keep and doesn't really owe me anything if it falls apart tomorrow. 

If you tot up the cost of bits made, it's paid for itself with all the screw cutting and machining.

Wheel spacers, collars, main stand pivot, side stand pivot bolt, engine mounting bolts, caliper bolts,  some in high  tensile stainless which was pushing things  it a bit.

Most useful tool next to the lump hammer and mole grips!

Regards
Dave

[exvalvesetdabbler]

I picked up the carb bodies from the vapour blasters today,  they came out as good as expected. here are a few pits remaining , but they can't put metal back on!  Bit of a balance between smothing out a few deep pits and not rounding off the sharp edges on the lettering/ keihin logo

Currently removing all the blanking plugs and giving them a buzz in the ultrasonic followed by drying off and a light spray with duck oil to preserve them for now.  It will be a few months before I can get the plating done.

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I haven't been slacking though, fuel tap body cleaned up and the brass nut nickel plated
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Regards
Dave

[exvalvesetdabbler]

Making a start on the electroplating.  A few test pieces I put through yesterday evening. This is my first time using commercial carriers and brighteners.

This is using the Gateros chemicals.  I only put 4ml of brightener in rather than 6 ml as per the instructions hoping for a less shiny finish hoping that would give better adhesion for the yellow passivate. (Which a lot of folk have problems with). I will have to push through some more clear passivate items first  to use up some more brightener.
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So far I am degreasing and stripping old plate off using a sodium hydroxide based sink unblocker in the ultrasonic bath followed by warm citric acid until there's no more fizzing. If they are then clean enough (water break test).just a minute in 5% HCl rinse and straight into the bath.  A few bits where rust is visible in any pitting, just back into the acid till it's gone.


Prior to passivation, 5 minutes in the ultrasonic using warm soapy water to scrub any residual brighteners from the surface followed by an acid dip.

Regards
Dave

[Johnny4428]

Looks like you are getting good results there. Nice work!

[exvalvesetdabbler]

Good results are still to come - or not  if the yellow passivate on all the carb bits doesn't rub off.

I have a Speedo base to do and hopefully that might use up some of the brightener and dull things down a bit.

Regards
Dave

[exvalvesetdabbler]

Hard to see what's going on in there with all the 'bubble bath' they put in these solutions. It got to the top earlier and had to poke it back down with a plastic stick.

I suppose I should just light a couple of stinky candles and relax until they're done.
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Regards
Dave

[DomP]

The Gateros kit is really good, its very satisfying when you get good results

[exvalvesetdabbler]

Finally got around to doing the yellow passivate the last few days after struggling with adhesion.

A few words of wisdom for  anyone using the Gateros kit especially the brightener.

DO NOT DUMP IN THE MAXIMUM AMOUNT OF BRIGHTENER FROM THE START

Initially I was aiming for a satin like finish more in keeping with the original so opted to add 4ml brightener instead of the recommended 6ml.  Things were still coming out the bath looking like chrome and the excess brightener film left on the plated items was making the passivate difficult to adhere. So the only thing for it was to do a couple of large items (Speedo bases) to pull some of the brightener out of the bath.(it gets consumed during plating, occluded within the plate and as a surface film).

To succeed with yellow passivate you only need a satin-dull plate coming out of the bath and even that brightens up after passivation.

The key seems to be getting bubble formation in the acid dip before the passivate. With the bright finish and using 5% HCl there were no bubbles at all even after a good minute in the acid, almost like the brightener film was acting as a lacquer.

With much reduced brightener levels in the tank, cleaning off the brightener film becomes easier and bubbles in the pre passivate acid dip make an appearance much quicker.  But you still need to wash it off well.  I have currently settled on using a warm detergent wash for about 5 minutes in the ultrasonic bath followed by a long soak in a jug of water. Followed up by a quick buzz using a mildly and dilute alkali degreaser.( 10% dilution of Elbow Grease Heavy Duty Degreaser).

Here's what they come out the bath before passivation
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Here's after passivation
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Other than the initial frustration it seems relatively straight forward but very time consuming.

I did feedback these observations to Dan at Gateros. Very helpful chap who looks after his customers.

Regards
Dave

[AshimotoK0]

Good tips there Dave and nice results. I have one batch of zinc electrolyte which had depleted brightener so I will try that out.
Yes I always find Dan at Gatetos really helpful unlike the guy at Youplate, who wasn't very helpful at all.

[exvalvesetdabbler]

For the barrel spring that closes the throttle and the torsion spring on the carb link rod, how do other people plate these?

Cleaning/pickling  , anodic stripping or  dunk in acid and prey?
De-brittlement, does any one do this?

And what about the hard steel inserts in the carb sync adjuster screws,

Regards
Dave

[exvalvesetdabbler]

Finally finished the zinc plating.
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I have tried to reuse all original components where possible but there were a few screws that had been chewed up and quite rusty.

I was unable to salvage the M5 screws that hold to the top cover onto the carb bodies, so I plated some small head stainless as screws.  I used a Woods nickel strike first and then into the zinc bath  immediately .
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This modern trivalent yellow passivate is not as good as the old hexavalent stuff. Even with the best cleaning between plating and passivation the colour does fade as bit if you rub it hard enough, but then the old stuff did to some extent.

Regards
Dave