A 3mm? Honestly, Matt, how hard was it to measure the diameter of the thread (major pitch) with a scale and go from there? (Take this in good hearted ribbing, not an insult. I have my moments too, too frequently.) You'd have found it was an M5, then from there the pitch will either be fine or coarse, which is clear by visual inspection... Just sayin' go buy a caliper, maybe a thread pitch gauge set and the like. FWIW the most common fastener on the bike (engine cases body work, etc.) are M6-1.00.

Oh, the "peanut butter" grade of the OEM screws has been known of for decades. The real curse was when they were use on the engine cases. Impact drivers were a way of life, as were drills and easy-outs. Never a bad idea to replace with socket or hex head screws.

I thought about buying a hundred screws of the float bowl size and selling them for cost here, just for the guys doing jetting. I can get them for a few cents a piece at Fastenal, but they have to be bought in lot sizes, not a few. I'm thinking maybe a buck for 4 plus postage. That would work in the U.S., then someone does it in Australia, got them covered. Of course you can find them at some stores that carry metric hardware. Just avoid black oxide - instant rust when exposed to the elements.

 

I don't have anyway to measure the screw (I don't have one of those bolt measuring plates at home) and if I took the screw out on more time I couldn't get it back in, which meant no transportation for me If I was 100% certain that Lowes would have the right screw I would have taken it out, but if in fact it was a specialized screw, then I would be stuck 6 miles from home without a throttle on my bike.

Conversely if I took the screw off at my house, I would have no way to drive to Lowes and get a replacement screw even if I knew the size. What a conundrum!

I agree with your peanut butter statement, my other carb screws are in surprisingly similar condition...

 

I was just pokin' ya! Buy one of each bolt they have! Oops, did it again.

It used to be a common thing for aftermarkett allen head screw kits for the side cases of bikes, just because the screws would strip out both because they were not standard SAE phillips, but were ISO (right?) with a different tip required AND they're so stinking soft!

 

I actually bought 4 types of screws and returned them all because they wouldn't let me take them outside to compare with the screw on my bike! the 5th buy was the charm?

 

Lowes or Home Depot are generally not too helpful. If you're in the states try a local True Value or Rocky's hardware. They're much more helpful and even sell you a cheap little plastic thread pitch template to show you how to measure whatever fasteners you may have..

Generally speaking you want a stainless steel socket head cap screw replacement on all Phillips head screws. Cap screws are commonly called Allen bolts. The first time I have a carb out it goes to the hardware store for replacement screws.



The higher sides make for a deeper pocket that will handle more torque. Button screws like you have are OK but cap screws are nice and deep. They work well with ball end hex keys (commonly called Allen wrenches) which can sometime round out the shallower pocket on a cap screw.

Many local hardware stores have really excellent nut and bolt selections and are staffed by knowledgeable friendly staff.

You'd also be advised to coat any external screw with anti seize. The screw is much less likely to seize up, will actually hold better and $3 will buy you enough anti seize to coat ever screw on the bike.

My rule is if it come out it goes back in with anti seize.

Find a helpful local hardware store with a good fastener selection. You'll be back there a million times.

 

A few years back, when I was building a Honda 305 Street Tracker, I took all my case screws and other misc. bolts, nuts & washers to Fastenal in a couple bags and asked them to match them with stainless socket head screws, washers & stainless nylock nuts. Left them the bags and they measured it all and ordered exactly what I needed. Had it all ready in a couple days and it was pretty inexpensive. I think less than $15 for everything.
One thing I learned by experience is not to use stainless nuts and bolts together without liberal use of AntiSieze. The threads will gall and lock up solid. From there you'll either have to turn them till they break or cut them apart. It won't happen the first time you put them together, but when you're either loosening or tightening them later on. Better yet, use stainless bolts and zinc plated steel nuts.
First time this happened was when I tried to remove the front axle clamp bolts. One was about 2 turns loose when it locked up solid. There was no room to cut, so I had to twist it till it broke. I took it back to Fastenal and they replaced it, even though we found in their catalog it warned about galling and recommended use of AntiSieze. Been using AntiSieze or regular nuts since then and no more problems.