Ok, so hears an update. BigJim is not a happy bunny so just gonna unload some stuff here then will be taking a break for a bit
Backstory is:- Replacement head purchased, get it blasted, stove enamelled,new cast iron guides,new valves collars collets and springs. First ride cut short, plugs keep coming loose. Head off and scrape out paint around plugs, plugs now do up tight and stay tight, progress, refit head and take for longer ride. loses power when holding at 50 and basically stops but not cutting right out, idles then returns home with less use of the throttle. settings on valve timing,ignition and carb are unchanged from before new head fitted and had been running well. Strip and clean carb, loosen tappets, try again, same problem. Remove head to check valves, bend 2 exhaust valve tops due to poor use of compressor (didn't know about the tap after light tightening, my fault, lesson learned). Walk away. Return with grinder, remove valves carefully. Wash the whole shebang in petrol to guarantee cleanliness, shorten life by a good few years with lung damage. Am reminded from years ago that inlets are larger than exhaust by Swarthy, useful stuff. Take a look at cut exhaust valves and see one is an inlet in size (marked as such on face also. I never checked when i collected it from engineer ( my fault, lesson learned). Steal a new inlet from old head (3000 miles since April) which seems to fit ok, not too much rock, and fit a new (cheap, not the expensive srm type) exhaust valve. Then as i about to fit i notice the vertical scoring on the cylinder wall!!. Only on the timing side but on both cylinders. Think bollocks to this and rebuild the bike anyway. Walk away and open a can and shout and swear for a bit.
Contact engineer today who does not comment when i asked him re inlet valve in exhaust port. Enquire further to check if seats had been cut which is confirmed. Had wondered if inlet had been fitted to exhaust because not enough meat in the head to seat the smaller exhaust valve?
So here's the rub, When i kick over the engine with plugs in and place my hands over the exhaust ports to check compression i can feel a large suction on the induction stroke in both ports, stronger in one, which i assume is the valves not seating correctly. The new cheap one is worst. Have set the inlet and exhaust tappets 2 Thou bigger, could this make a difference?
In conclusion am taking a break from the bastard thing for a day or two. Have been fantasizing about taking the big grinder to it and getting the Mrs to film me and post it on you tube. The bottom end was built by the most expensive engineers i could find ( no names here). The engine has covered approx 3000 miles since April, did have a dodgy cam ring for about 10 of those (my fault). The reason for the replacement head is that i was sold the wrong bolts for the Rocker box and damaged the threads on the old head.
I can predict how the responses, if any, to this post will unfold. Some people just shouldn't be allowed to own a classic bike, and i'm obviously one of those. Call me a " previous owner" and all that entails but please bear in mind i have never owned one of yours.
In th words of the great sage and eminent engineer Berger "thank you for listening, time for a black and tan".