Hi everyone,

I took apart the front wheel of my '77 DT400 as the aluminium rim has a deep crack in it. Sadly I forgot to measure the offset before taking it apart, I snipped the spokes as they were seized. What should I do? I'm looking at a new Excel Takasago Rim for the bike and I understand I need the offset for it for the wheel to be built up again. I'm planning to get the wheel done by someone else as I have absolutely no idea how to lace rims. 

Thanks in advance

Normally pretty much centered but I can't say for sure on that bike.  You could put the hub on the bike and measure how close to centered it is?  If hub is centered in the forks, then wheel is centered on the hub.  

If hub is offset in the forks, you should be able to figure out how far to offset the wheel on the hub to center the wheel in the forks.

OR, you could send your hub to Buchanan's.  They are experts that have been around for decades and can provide and install a new wheel with stainless steel spokes and you know it will be done right.  

Welcome if your new. I'm old--very old lol.
I've got "77 DT250 forks & wheel in my much older 360 so did a measure up.
Looks like years ago i built a gold rim onto it unless it had one but i dismantled & cleaned the spokes up on the bench grinder wire wheel so of course they started to rust after that didn't they!!.
Still good though. So take this result with a grain of salt but see what others say.
With a long straight steel ruler up the RH side [non brake side] i got 25mm from ruler to the rim edge as it meets the tire/tyre. On the brake side i got 20mm taking a line on the edge of the brake drum with my ruler.
Bit hard in the bike but confidant the brake edge was ok where i managed it.
But wait--there's more. It looks like the tire is about 5mm closer to the right side. So going by that theory 25mm should be 30mm & 20mm should be 15mm on the brake side.
I guess ya wishing you hadn't asked now & i'm psyched out now because my tire is closer to the right.
I'll load the pics i took of the wheel plus the bike so ya can have a laugh lol.
i didn't have enough hands to hold the phone & two rulers. 
About time i gave it a clean out down the paddock or give a good rev tomorrow while neighbors are at work.
photos.app.goo.gl/6W38H74zwXK8ANRc6

Thanks to both of you for your help and apologies for my super late

Turns out I've got a 78' model as that is when this bike was first registered, according to the documents I got with the bike. (Bought it in Germany) I think I got too excited with starting work on the bike and forgot to read the docs that came with it

I eventually bought a donor DT400 as it had both wheels and some other parts I needed for my own project. Measured the offset for the donor front wheel (specifically the gap between the side of the rim and the straightedge that was placed flat upon the drum of the hub (was pretty much bang-on 20mm) and only then took it apart.

I cleaned and serviced the hub I was going to use for the wheel, ordered new OEM spokes (ooo shiny) and cleaned up the donor rim, put all of the parts in a box and sent them away to get laced and trued! I live in the Netherlands (my DT400 is interestingly an Austrian-spec model with Austria-specific indicator lenses) so the obvious choice for me is to send it somewhere more local-ish. Even though I've read good things about Buchanan's

RT325, your bike looks rad, looks like a true survivor. Thanks for taking the measurements for me. I'm glad I asked as if I hadn't been able to measure the offset myself I would have been okay with your specs!