Video -- of my DIY 90-degree screwdriver carb sync screw tool

[DogBunny]

This one is short and sweet. Clocks in at a svelte 3 minutes and 45 seconds, and 45 seconds of that is of a running XS650.

It's a tool specifically for getting at that hard-to-reach sync screw between linked carb bodies, and if I do say so, it works well. Easy to get on and keep on the screw slot while you're turning it and looking at your vacuum gauges.

Not sure why I made the vid -- I don't expect anyone else is ever going to make one, even though it's pretty easy to make. At the end of the video I say that I'll show the fabrication details in PART II of the video (I documented it all while I made it), but that's probably not going to happen unless a lot of people make two extra clicks -- one click to watch the video on YouTube, and another click to "like" the video (on YouTube).

 

[WideAWAKE]

Top notch!!!!

If I had a bike with linked carbs I’d definitely make one.

 

[Mailman]

I think that’s brilliant! That screw always was a pain in the but to access.

 

[DogBunny]

I have already made a huge improvement. This changes this screwdriver from a kind of fun and cool but non-essential item, to a critical tool IF YOU HAVE BS34 CARBS. I am modestly calling the improvement the DIY 90-Degree Carb Screwdriver Mark II, version 1.1

Since it looks like I will never actually make the Part II YouTube video, let's back up and take a look at the handle construction of the original screwdriver:

The handle consists of a dowel cut in half. A drilled hole accepts the copper tubing, and a carved groove accepts the cable.

The drilled hole is LARGER than the copper tube, so the handle can rotate on the tube. The carved groove is SMALLER than the cable, so the handle clamps the cable.

I assembled the handle halves together using a black zip tie on the left. I tried another zip tie on the right, but it didn't clamp the cable sufficiently, so I had to change to a hose clamp. In-between, I put a piece of shrink-wrap, purely to make it look better. The black zip tie was also for aesthetics -- it looks nicer than a hose clamp.

Now for the Mark II. It occurred to me, that if I ditch the piece of shrink-wrap, and use another hose clamp instead of the zip tie, that now I can easily disassemble the handle, and swap in a different cable, with a different screwdriver tip soldered to it.

Why? Because with a much smaller screwdriver tip, you can use the tool to adjust the "air-mix" screws on BS34 carbs.

The mix screw on a BS34 is a BITCH to adjust unless you remove the tank and use a remote fuel source. I have NEVER been able to adjust it with the tank on. I have tried all kinds of various 90 degree screwdrivers, fixed ones, ratcheting ones, one I made myself, they all SUCKED and were totally unsuitable for reasons that I won't waste my time explaining here.
The problem with using a remote fuel source, is that you can't make road-test type adjustments on the fly, for example, trying to tune out a slight pop on decel -- after perfectly dialing everything in with vacuum gages in the shop, you might find that one of the mix screws has to be opened up 1/4 to 1/2 turn to correct that decel pop. Which I like to do during a road test, with the tank in place.
So, I already checked clearances -- my existing tool, with a smaller tip, will fit, and should work fine. About to get to work on it straight-away.

 

[Mailman]

The necessity of invention is a mutha! Or something like that. Really nice work!

 

[Superdriver]

This one is short and sweet. Clocks in at a svelte 3 minutes and 45 seconds, and 45 seconds of that is of a running XS650.

It's a tool specifically for getting at that hard-to-reach sync screw between linked carb bodies, and if I do say so, it works well. Easy to get on and keep on the screw slot while you're turning it and looking at your vacuum gauges.

Not sure why I made the vid -- I don't expect anyone else is ever going to make one, even though it's pretty easy to make. At the end of the video I say that I'll show the fabrication details in PART II of the video (I documented it all while I made it), but that's probably not going to happen unless a lot of people make two extra clicks -- one click to watch the video on YouTube, and another click to "like" the video (on YouTube).

Excellent. Thank you. Bill

 

[DogBunny]

I decided to make a second 90-degree screwdriver. The new one (the smaller one above) is dedicated for the BS34 mix screw, and I can still use the original one for the sync screw while fiddling with the mix.

I built the new one from this Harbor Freight "precision" screwdriver set, which I bought a long time, probably $4 or so at the time.
This turned out to be a pretty crappy kit, with non-hardened tips, and a gimicky flex extension which I never used.
However, the handle, and the cable inside the flex extension were perfect for making my new 90-degree screwdriver. Having an already-made handle reduced the construction time of the new screwdriver by about half.

https://www.amazon.com/Pit-Posse-Motorcycle-Carburetor-Adjusting/dp/B004N0EX7Y
BTW, if you have more money than time, you can buy yourself a 90-degree screwdriver. At the top of the price range is this Pit Posse set. It is geared. I've handled one, and it is very nice. Comes with multiple quick-change tips.

https://www.amazon.com/Motorcycle-C...-08-0119/dp/B074R9F6KD/ref=asc_df_B074R9F6KD/
Next, is this Motion pro. Cable drive, and single-tip, like mine.

https://www.aliexpress.com/item/3256804066013620.html
If you want to really cheap out, I found this one on AliExpress. Less than $15 shipped, but the whole point of the ones I made is that they didn't cost me a dime.

https://www.aliexpress.com/item/2255801172287090.html
While searching Ali, I came across this. It would be pretty easy to make a geared 90-degree screwdriver like the Pit Posse one.