I used 10mm OD Viton O-rings with a 1.5mm cross section and I got them from McMaster - P/N 9263K295. I do have some spares so if you're interested, shoot me a PM. Listed O-ring dimensions are often nominal or "as installed", so before I cut my grooves, I measured the O-rings to be:

 

.401OD

.281 ID

.060 cross section

 

With that info and a little trial and error, I cut my grooves to be .286 deep and .063 wide.

 

I also checked the size of the throttle plate screws. They are brass screws M4 x 0.70 x 10 mm long (approx.) and they're thread deformed at the tips for retention. I'm guessing that's why one of yours snapped off? Did you get a half turn or so before it locked up or did it snap right away just from crud in the threads?

I edited the info into the above post, but that doesn't bump the thread. So I'm bumping now it so you know I've been back.

So this rookie gets the screws out of the throttle plate but looks like I damaged 1 of them on the way out but didnt realise. I put them back in and 1 is getting really stiff so by the time I start backing it out the head breaks off. Stupid mistake because I know better but just too excited a guess. Hopefully I dont need another throttle shaft.

 

Thanks for the guide and I will sure to give it a try.

I hope you can get the screw stub out of the throttle shaft. The threads on the original screws are purposely deformed at the tips after the initial installation. This is so they don't accidently come loose and get sucked down your carb throat. You can usually get them out, but they can be a little tough to get started correctly to reinstall unless you clean up the threads a little. Sounds like you cross threaded it... Might not be good.

 

And about my dimensions above... I want to point out that I'm operating in a non-professional shop with uncalibrated measuring tools. Because of that, my measurements could be off a couple thousandths from what you would get with your measuring tools. My RELATIVE measurements were spot on, but the absolutes could be off some.

 

By that, I mean...

 

I cut all of my grooves spot on at .063 wide and .286 across at the narrowest point. I know that because I used the same measuring device for all the work. But in your shop with your tools, you might measure .064 wide and .285 deep. Or something else the other direction.

 

The point is... Use my uncalibrated absolute measurements above as a guide only for getting close, but determine the last couple thousandths in either direction with a test piece and trial-n-error in your shop with your measuring tools.

 

Hey Bruce,

 

You are talking about calibrations to a metrologist so I already took your measurements only as a guide. The reason I live in Barbados is because I work for an organisation where I am responsible for improving the calibration capabilities of the labs within the Caribbean. My previous job my background was calibration of pressure gauges, force equipment, torque wrenches and gauges along with some flow and volume work. Since I am now a paper pusher this is the only way I get to dirty my hands and have some fun. Gratefully there are guys like you that already did all the research so I get to do and not think so much.

 

Everything I do would be relative to the o-rings and the shaft diameters as indicate by my instruments. The key is that I want a sealed fit between the o-ring and the bushing. Problem is in Jamaica I would have access to a machine shop. Here I will have to use a drill press and hack saw blade to make the grooves.

Excellent. So you already got a good handle on the measurements stuff. Better than I do, I'm sure!

 

I'm a little concerned about the plan to use a drill press and a hack saw blade to make the grooves though. I understand you gotta make do with what you have available, but O-rings are one of those things where a thousandth can really make a big difference and I'm not sure you'll be able to achieve the level of precision desired to make this work properly. Fit and finish are both important.

 

Do you have any access to better facilities in Barbados? Maybe you could take the parts to one of your metrology customers with some machine tools and tell them it's a test piece to make sure they've got their calibration processes under control?    I've been to Bridgetown. I wasn't there for anything industry related so I wasn't looking, but the city is big enough that there has to be other means available. For a cost of course.

There are machine shops that I can have do this for me but that would be taking all the fun out of bringing the carbs with me to Barbados. The reason they are here is for me to get my hands dirty. I will check it out and see as I think I will take the broken stub to the machine shop so I dont do any further damage.

I understand. I probably get my hands dirty more often than I should. 

So since I am new to the forum I will reiterate the obvious that Captain Obvious is a great guy. This gentleman, who I am still yet to meet, sends me a few odds and ends to help make my carb refresh that much better. Bruce I salute you sir and table a motion to promote you to Major Awesome!

Haha!! I'm not looking for any promotion. That just means more responsibility for not enough pay. I like it right where I am. 

 

Good luck with the project and remember... If I'm ever in Barbados or Jamaica, you're on the hook for the tour! 

i second the motion - a very good man, and a super resource for this forum.

Just as an update I still have the throttle shafts to machine but I have been putting in some work on cleaning up the carbs. So far I have spent a few hours on the dome with an assortment of sandpaper and I like it. I may try some polish but I love the bling so far. Anyone who has done this before, should I clear coat the domes?