The thread probably could be retapped but I never have done any retapping before and would prolly have to pay someone $150 to do it for me this day n age.
I put a thin amout of jb weld on the threads down in the hole, I will attempt to set the screw down in later today after it sets awhile.
I need to get into the tap retap.  I need to put a second spark plug hole in a dt400 head for a compression release also.
Dan

Think of a price for the one with a new needle/seat and if you want to get rid of it, I may just buy it.

Tapping a thread is the same principle as what you're going to do with the JB and a screw, albeit with slightly more specialised tools.

I bought used good quality taps and dies and, together with my pillar drill, are some of the best buys I've made.

Here is a link to my thread on the carburetor conversion, when I get back to my house in a couple days let me verify what exactly I have and I will message you with pictures and prices.

www.yamaha-enduros.com/index.php/forums/...-alternative?start=0

Hey Dan, I'd like to see a picture of the head after you drill and tap it for the compression release, I'd like to do the same to my DT400.

DT400 has the kick start operated compression release for starting in the front of the cylinder. Is that working. Do you want one in the head for another reason--to scare pedestrians etc by operating with a cable & lever. Or just one of those chainsaw type to push in & they pop back automatically.
Stripped thread in the pilot air screw hole would be a 'first' as they're never screwed in tight. Was it all corroded & crumbling on moving the screw.

I haven't drilled it yet but got this far.
You can see where there is spot in the casting to put the hole.
I had to cut away part of a cooling fin that was going over it.
The shiny circle is the spot for the hole.
I don't think all the Enduro heads have that, I know my 250 does not.
Dan 

I used to have 2 webco heads for the 400's.
I hate myself for ever selling them even tho I got big $$ for them.
Dan

I intend to put a cable operated one on mainly for sound effects going down through town.
I know it's silly.
But I hardly ever use the brakes on the 400, even less so with the release.
Dan

I intend to put a cable operated one on mainly for sound effects going down through town.
I know it's silly.
But I hardly ever use the brakes on the 400, even less so with the release.
The screw or hole had no real corrosion, but the threads weren't grabbing but the screw looks fine.
I ran the screw in after the jb set all day, it took considerable force, I got it to bottom, the back out 1.5 turns and it stayed time, hopefully it holds.
Dan