Valve location screw repair

[Sambo]

Apologies if this has been covered, but I couldn't find anything on the search function.

Since owning my rapid, the valve location screw has been a bit sloppy in the threads, im worried its only going to get worse and cause problems.
I think mines and early mk1, can anyone advise the best way/size to re-tap it, if this is even an option?

Cheers, Sam

[Squinty]

Simple fix is PTFE tape on the grub screw, unless its totally gone or you're a serial tinkerer (like me) how many times are you likely to unscrew it?

[Sambo]

Nice one thanks..
Thing is I've unscrewed it about 10 times in the last few days as I have a leak i can't seem to sort!
It sarted leaking through the barrel so I gave it a clean and changed the o-rings on the valve and housing  as this seemed to fix it last time. But when back together it was leaking from the location grub screw and the barrel!
I think there's something going on with the valve housing to be honest, as I noticed there should be a smaller o-ring on it and mine hasn't ever had one on, just the 1 larger o-ring.. is this normal?
As when I tried to put the smaller o-ring on the valve housing it seemed to knock the alignment of the location screw out, in such a way that explains why the threads to the location screw are a bit knackered and the previous owner might have left the smaller o-ring out?

I've just ordered a new valve assembly in the hope it will sort everything out!
Will try the ptfe too, cheers!

[Squinty]

funny that you should mention the tail o-ring- in a previous thread one of the members quoted a message from Ben Taylor who said  that later blocks didn't have an o-ring as black acetal didn't need one.

Depends how old yours is I guess- 98 onwards,  2000 technical sheet doesn't list a 4.1x 1.6 o-ring in the acetal valve service kit.

[KevG]

an easy fix for damaged thread in the mk1 block is to run an m4 tap through the damaged thread no need to even pre drill it original thread is 4ba,then use a m4 grub screw.
KevG

[angrybear]

If you re tap the thread remember to turn down the end of the bolt to fit in the location slot of the valve.
remember that bolt is not to secure the valve only to locate & align it.

[Sambo]

Thanks for all the help guys, I really appreciate it!

Squinty- that's interesting, when I saw any pictures they all had the tail o-ring and I started to wonder, but its worked perfectly for me without one before.. so I guess as long as I replace the housing with another acetal one I don't need the tail ring..

KevG - Thank you. This is exactly what I was thinking, but wanted someone like yourself to confirm that this is okay to do. Cheers.

Angry bear - thanks, i did sort of all ready consider this, I was going to try and use a 5mm nylon tipped grub screw that should fit nicely.

Thanks again for your advice guys, a big help, hopefully next week she'll be all good again!