changing to usa threads on some of the bike:

Not open for further replies.
Feb 21, 2005
Greetings from wet, windy Cape Cod.

the 71 basketcase is coming along as funds and time permit. Frame is painted, engine and tranny rebuilt and back in, Oil tank and battery box are all painted, clear coated , and back in the frame, Z plates back on ( I even painted the spacers between the frame and Z plates, tanks and right side cover is primed, waiting for better weather to do color coats..... My main problem was borrowing a friend's baldor polishing system: I had a ball polishing all the covers etc: it really is mesmerizing to do the polishing and I'm glad I didn't have to resort entirely to elbow grease.

Today I rebuilt the original amals. Upcoming daughter's wedding precludes getting the Mikuni retrofit at least for a while so I went nuts with the polishing wheel and cleaned/rebuilt the old carbs. I did two things that I don't think will come back to haunt me, but maybe you have other experiences.

I chased the threads on the carb body with a standard 10-32 tap and bought off the shelf stainless allen head cap screws and lockwashers for the carbs, then I chased the 5/16x18 intake threads with a USA tap and installed more over the counter stainless allen bolts and lockwashers.

to my way of thinking, if something were to work loose on a ride, I'd rather go to the local hardware store and pick up a bolt than have to order some special order exotic part, especially when the size difference is so minute. everything looks great, feels plenty tight .

I did the same for the clutch inspection plate and switched the original rocker cover bolts for 1/4x20 stainless cap screws as well. looks good and I think I saved myself a bunch as compared to ordering all those allen sets from oldBritts or British cycle supply.

do you think this will cause any problems on the long haul ?

just waiting for a little more doe so I can get all the electronic stuff and be actually CLOSE to firing it up :)

I don't know man.... Shinny parts are nice but unless the threaded holes are damaged, and you can’t find a Heli-Coil that is the proper size… don’t change for change sake. I’m not trying to be a Concourse Nazi, but if you ever want to resell the bike, the next owner might not think your ideas are proper English! 10-32 tpi might not have enough thread bite in soft aluminium parts or pot metal that the Amal’s are made of. I would rather spend the few dollars on spare bolts that are made for the parts and then keep your old bolts as back up. Put them in a small container in your bike if you plan to venture on long distance trips.
Shinny parts are nice but unless the threaded holes are damaged, and you can’t find a Heli-Coil that is the proper size… don’t change for change sake

You make a good point, but as I understand it, it's a matter of going from 55 degree thread pitch to 60 (or vice versa, I can never remember) and the bolts I changed over (except for the intake manifold bolts) are all relatively non structural. I tested the 5/16" thread conversion on a Z plate bolt to be sure prior to tapping any others. I torqued the heck out of it looking for structural failure (and I was in the boiler room in the Navy so I KNOW how to wreck a bolt if I need to) the retrofitted fitting held very nicely.

My bike is being built up to be a 'runner' not a show-er, so councourse correct parts are of no matter to me. it was a total rust bucket when I rescued it from leaning against a barn in Virginia, where it had lahguished for 20+years. There was an inch of red clay in each cylinder, every nut and bolt was corroded and nearly unusable. but surprisingly, the engine internals were really quite good. Since I'm a true New England Yankee (read CHEEP) it just made sense to go with locally obtainable parts where I could safely get away with it. I didn't mess with any of the hardware involved in the engine build.

thanks for your feedback

Karl hoyt
I don't think you will have any problems with the intake manifolds or rocker covers and inspection plates, but the small screws into the concentrics might not have enough strength with the damaged to the threads in the zinc pot metal. I have seen the originals strip pretty easily and the vibration makes it worse. The result of failure here is gasoline dumping from the float bowls onto a hot engine. Not a pretty sight.
hey basketcase wondering if you have any photos of the buildup you could post or put on a website such as boganpages on the website or even photobucket as it would be good to see some build up pics.

I have some pix of the original beast leaning against a tree in my back yard and once I get the tank finished, I'll post some pix of the build as it is now: I'm a part-time musician and the gig season is upon us, which means more $$ to put into the Norton :p so I hope to be kicking it over by July or so.... right now it's just a frame and mostly reassembled engine (but all shiny !!!!) . In the next month or so after I relace the wheels and install the boyer and electronics, I'll get some decent pix !

thanks for all the feedback on this issue, folks

Not open for further replies.