Valve adjustment problem

[Gecko]

Having suffered some vibrations I thought it was time to adjust the valves again and to confirm my suspicions they did need doing. Right hand side went well but as I got to the left , the upper exhaust valve presented me with a problem. It was very tight (no play at all) and having slackened it off (which lossened off quite easily) I now find I can't adjust it. It feels like the threads are stripped - it tightens up to a point then slips loose again.
So the question is , which bit do I look at replacing ? Is it just the adjuster screw or will it likely be the rocker arm assembly and how the heck do you get it out ?

 

[Trullion]

My guess is that someone has overtightened the locknut, stripping the thread. For years I have tightened my valve locknuts by feel. About two years ago I thought I'd do it 'properly' and use a torque wrench. Problem was that the torque setting on the maintenance sheet I keep in the garage was wrong. It was overstated by some margin because some idiot (Moi) had typed it incorrectly. Result of using torque wrench: one stripped thread.

Unfortunately AFAIK it isn't possible to remove it without taking out the rocker arm. From memory the adjuster can then be unscrewed from underneath the rocker arm when it has been removed, which is straightforward though annoyingly time-consuming. I obtained a couple of used adjusters and locknuts from Motorworks for not a lot, though the case hardening on one of them had worn through. An alternative would be to buy a new or used rocker arm complete, but I preferred to keep mine as there is no wear or marks on the bearing surface and it was a simple enough fix just to replace the b*ggered adjuster.

Since then I've gone back to using 'feel' to tighten nuts, using a torque wrench only for high torque, critical fastenings such as head bolts. There have been no issues with the replaced valve adjuster.

Hope this helps.

 

[Gecko]

Thanks, good to know I am not alone with this one...

I have the rocker out now and am off to see if I can get a spare part ... were there any special problems to be aware of for reassembly?

 

[Trullion]

No. At least, I don't recall any. You should check and if necessary adjust the end float on the rocker shaft before accurately adjusting the valve clearances. Minimum spec (2 thou from memory) should give you a nice quiet top end. There are several threads on this forum re how to do this if you haven't done it before, though it's not difficult.

Good luck!

 

[Gecko]

Picked up a new rocker adjusting screw and nut from the dealer and got on with pulling the assembly apart. It wasn't too bad really. The screw was needed to be hack sawed out but that was no trouble and the new one went in nice and easy and feels good again.
I'll have a look at adjusting the end float on the rocker shaft tomorrow. I ran out if time today but thanks again for the help.... so far so good