How do find the inner diameter and/or wall thickness of a frame?

[rottenprimate]

1981 GS450SX

I need some slugs, do not have a lathe unfortunately. Trying to find some rod that might work or SOMETHING. But need to know what size to go with. Thanks!

[uk gs nut]

There are drain holes at bottom of the frame, maybe that might help.

[Redman]

. . . . . . .

Makes me wonder what you are monkeying around with.

.

[Rich82GS750TZ]

OP= rottenprimate

Makes me wonder what you are monkeying around with.

I see what you did there Dave, and I approve.

[rottenprimate]

Makes me wonder what you are monkeying around with.

Well I plan on chopping the rear of the frame off. There is a new and very obscure style of bike called a “cafe racer”. I consider myself a bit of a pioneer in this style.

I suppose it won’t be much of a problem. Chop the frame, try stuff till it fits. but I would like to make sure I can get the right size before I go chopping.

[Rich82GS750TZ]

There is a new and very obscure style of bike called a “cafe racer”. I consider myself a bit of a pioneer in style.

Do tell. We’d love to see some pics of your builds. There are a few members here who’ve done some very nice café mod builds.

Not sure about “new and obscure”. You’d have to live under a rock to not know that it’s a thing.

[rottenprimate]

Do tell. We’d love to see some pics of your builds. There are a few members here who’ve done some very nice café mod builds.

Not sure about “new and obscure”. You’d have to live under a rock to not know that it’s a thing.

That was a joke. This is my first build. I’m not a fan of every aspect of a cafe racer. I’m not entirely sure what I’ll end up doing yet. I do know that I’m gonna lob the back of the frame off and need some slugs. I will definitely start a thread when I get the build started. I’m just waiting on a few things. My bike is a POS and needs a ton of work. I bought it for $200 mostly for the learning experience. I have an actual functioning bike for riding.

[Rich82GS750TZ]

Ok. Sorry. It’s difficult to read sarcasm in print. Anyway. Welcome to the forum. I don’t know what the ID of your frame tubes are at the back of your bike but someone here probably does.

You’re in the right place to learn. Tip on using the site’s search function. Always used Advanced. Always change to search Titles Only for your key words. You may find the answers you seek.

[salty_monk]

I think they are 2mm wall thickness tube but I may be wrong....

[Baatfam]

If indeed your bike is a "POS" needing a bunch of work, would it not be prudent to do the bunch of work first?
You know, make sure it goes, handles, and stops correctly? You can always start chopping later.
I only suggest this, because I've seen folks run out of money trying to make their bike "look" right, before they get the bike running right.

[cowboyup3371]

If indeed your bike is a "POS" needing a bunch of work, would it not be prudent to do the bunch of work first?
You know, make sure it goes, handles, and stops correctly? You can always start chopping later.
I only suggest this, because I've seen folks run out of money trying to make their bike "look" right, before they get the bike running right.

+1000 on this - get the bike running properly first

[rottenprimate]

If indeed your bike is a "POS" needing a bunch of work, would it not be prudent to do the bunch of work first?
You know, make sure it goes, handles, and stops correctly? You can always start chopping later.
I only suggest this, because I've seen folks run out of money trying to make their bike "look" right, before they get the bike running right.

you are correct but unfortunately part of getting it up and running again is a frame repair on one spot which needs a new piece of tubing. Cosmetics are the last thing I’ll be doing.

[Gorminrider]

find ID at drain holes was a good idea iOR just drill a small hole at one at those "rear of seat" places where you're going to cut it off and push in a small rod. Subtract the thickness of the steel at the hole=ID

[GregT]

2mm wall thickness is plenty for a rear subframe - even with a pillion and suspension pickups.

On my roadracing frames I usually use 16gauge - 1.6mm wall - mild steel for subframes.

When you say you need slugs, I'm assuming you're going to use inserts at tube joints. Unless you're lucky, you probably won't find the correct OD tube to use there.
When I have to build a frame in sections with joints on straight pieces using inserts, I almost always have to machine thickwall tube to suit.
Finding the correct tube in the very small quantities you need can be impossible - and you don't need the balance of a full stick laying around for ever....