rebuilding carbs

[exvalvesetdabbler]

I have been digging through my boxes of bits and found enough bits to put together a set of carbs.

I'll post what ever I get up to on this thread as I go.

The first job was to refurb the frame and link rod that was stuck fast.  Loads of soaking in various fluids and wiggling to get some movement. Made up a jig to drill out the pin so that the link rod could be extracted.  Then drill out the hole to 4.4 mm and tap M5.

The jig keeps the drill centered.  Drilling out a steel pin from aluminium can result in the drill wandering off centrer.
[ Guests cannot view attachments ]
Stepped screw to lock in the link rod.
[ Guests cannot view attachments ]
Remove the felt seals and retainer
[ Guests cannot view attachments ]
Link rod. This is after 2 days in my electrolytic cleaning bath to de-rust an clean.A bit scabby where the throttle linkage is attached bit at least the bit that engages with the bushes has survived. I'll probably just brush plate this portion.
[ Guests cannot view attachments ]

Regards
Dave

[exvalvesetdabbler]

Time to separate the two halves of the throttle cable rotor.  I learned from previous experience that acids and plating solution can get trapped between the two halves resulting in corrosion creeping out the cracks.

I center punched each rivet and drilled out using a center drill. Any residual around the hole can be sliced off with a sharp blade and the remaining rivet on the other side can simply be pressed out.

A center drill with a tip just under 3mm is an ideal size.
[ Guests cannot view attachments ]
[ Guests cannot view attachments ]

[exvalvesetdabbler]

The original retainer rings for the felt seals weren't that great and it was easier to make some new one out of stainless.

[ Guests cannot view attachments ]

I will still try to re plate some of the old ones but I suspect that once they have been cleaned and pickled, there won't be much left of them.

Lots of. De rusting and electrolytic cleaning to do. Sodium carbonate, dash of oven cleaner and washing up liquid. It's a slow process but saves on a lot of scrubbing.

[ Guests cannot view attachments ]

Regards
Dave.

[Laverda Dave]

Nice work and well done for putting in so much effort to overcome the problems.
I can see you recieving order for those stainless felt retainers 👍

[Murf]

A lot of good ideas there, I like your electrolytic cleaning, will you be replating the parts yourself?

[exvalvesetdabbler]

Jury is still out on plating,  depends if I can get a worthwhile batch together to send them out. Also there's a lot of small bits to loose.   If I do them myself, I need to  refine the brighteners in my tank to get a level finish, and probably try out an alkaline bath for better throwing power to get into all the nooks and crannies.

Regards
Dave

[exvalvesetdabbler]

Most bits cleaned, rust removed.  This is the state I would have them before sending off to the platers or plating myself. Flash rusting shouldn't be a concern so long as some residual plate remains. That's the beauty of this clean up method, it removes rust but leaves zinc plate in place.

[ Guests cannot view attachments ]

Regards
Dave

[exvalvesetdabbler]

Nickel plating the ends of the carb link rod.  These are quite a soft steel that has been hard chromed and since it's only the end bits that are the worst and in plain sight once on the bike, I decided to clean those up and apply a coat of nickel.

Because of the inverted cone on each end, simply dipping the end in plating solution just trapped bubbles and didn't cover well.  I came up with this method using a cable gland to create a cell around the end.  The bit above the gland is the nickel anode.

Slow going at 10-15 mA but it seems to be working.

[ Guests cannot view attachments ]
[ Guests cannot view attachments ]

Regards
Dave

[exvalvesetdabbler]

I had a, little win today, been figuring out how to cut the felt seals while keeping the od and id concentric. Cutting the two holes separately was not reliable.

[ Guests cannot view attachments ]

The solution was to make the two cutters fit inside each other. The outer cutter does the outside diameter and retains the circle of felt.  The inner cutter is chamfered internally to cut the inner hole to the size needed.

These are cut by squeezing the cutter against hard plastic in the bench vice so no bruised knuckles which is a bonus.

[ Guests cannot view attachments ]

This is the felt that I found.

[ Guests cannot view attachments ]

Just need to do the same for the carbs link rod and the throttle slide arm felts.

Bit of a faff making up tooling but should be able to turn them out like sausages.  I was tempted to size the cutters to the same length so that a felt washer comes out in one hit, maybe later

Regards
Dave

[exvalvesetdabbler]

Been making replacement interconnectors to replace the old plastic ones that some folk have been reporting breakages for.   I also compared the measurements with the T connector which is brass. On the old plastic ones, the groove width was narrower as was it's inner diameter. Not really sure if the old plastic has shrunk with age or just naff machining tolerances.  I made the new ones to match the grooves in the T connector.

A bit of faffing around grinding a groove tool for machining brass to reduce the rake angle to near zero, a sharp contrast to what I have been using for stainless.  The tool tip was honed on an oil stone to remove grinding marks that would otherwise show up on the finish of the groove.

Nearly finished after deburring
[ Guests cannot view attachments ]

Finished item
[ Guests cannot view attachments ]

Don't think I could make a living doing these, the first one has taken most of the day in between the crisp, biscuits and coffee breaks, on the plus side there were no rejects. 

Number two tomorrow.

Regards
Dave

[taysidedragon]

Nice work. Quite fiddly I imagine.

[exvalvesetdabbler]

Measure 5x cut once!.

[Laverda Dave]

Nice work 👍. If you had a CNC machine and a program I bet you could batch manufacture these. There must be a demand for them because the plastic ones get so brittle they break for fun. I bet DSS and CMSNL would be interested?

[exvalvesetdabbler]

A milling machine would be my first choice if I had somewhere to put it, but yes you're right if someone with CNC capability took it in they could churn them out like sausages.

I had a lot of similar items made at work in titanium and despite the high material cost, the tooling/setup costs always dominated for small batches of around 30.

Regards
Dave