Idle mixture screw thread size 78-79

[bikerphil]

I am trying to fix the damaged threads in an early style carb (78-79) and the threads are an unusual size. Does anyone know the exact size of the metric tap needed to repair this?

[DiverRay]

I'll try and find it, but I know it's NOT an easy tap to find! I couldn't find one a few years ago, but I was able to replace the body with one of my spares.

[cajun31]

Couple questions. Do you have the replacement screws in hand? Do you live close to a hardware store such as ACE hardware, Lowes or Home Depot? If the answers to these questions is yes then take the spare screw with you to one of those stores and just size the screw. I do that all the time when looking for replacement screws etc.. Lowes and Home Depot have threaded guides with all the different and common sizes.

[red bandit]

M5 X 0.5 It's not a standard thread but it is a common thread. A hardware store would probable not have one in stock but might be able to order one. Otherwise a tool supply house. J&L (their shipping is killer) or what ever you can find in your area.

[bikerphil]

Yep, no hardware store I went to has anything close to it. I was sure of the the thread pitch being 0.5 as I have a gauge to measure metric thread pitch, I just wasn't sure of the bolt size. So it is M5X0.5, I'll buy one online, Thanks fellas, much appreciated.

[Bax]

M5x0.5, you'd probably want the plug or bottoming chamfer for the carb so you don't wreck the seat

---Bax

[bikerphil]

Well, it's just the first few threads on the top that are messed up. I don't think the threads go all the way down as the tip on the screw below the threads is pretty long. Thank you for the chart.

[bikerphil]

OK, not in a big hurry to fix these carbs, they are a spare set for a friend, taps on the way from China. Thanks again red.bandit for the exact size of the tap.