Folks : I bring good news !!! .... There is no God! *
 
Now get used to that fact ....  and get on with your lives!
 
*Seriously ...
- No God has done anything for the last 15 billion years - the chances of you incurring his wrath in your lifetime are slight.
- No God was necessary to create the illusion of the "big bang". Its a stretchy,"time dilation" thing.
- Study quantum mechanics, relativity and statistics. Then sit down and think about it for a bit.

Tight valves are more of a problem than loose ones...
 
if they're loose then they close early an open late ... It rattles a bit a looses some performance - no harm done.
 
if they're tight then they close late (or not at all) ... The result can be burnt valve seats and even 'blowback' through the carbs.
 
Blowback is highly amusing (and destructive!) and involves smoke and flame emerging from your air-filter 
 
Yours sound tight ... I'd measure them again... They don't usually go tight, apparently.

Big backfire suggests its fuelling properly but not igniting... points to an electrical problem.
 
That would suggest that there's some vital wire somewhere that is making intermittent contact. That's not unusual on a 10yr old bike.
 
Some possibles...
 
+12V or earth to the coils.
The timing lead from the pickup in the engine left casing.
Corrosion in the ignition switch.
The immobiliser plug (or frayed wires to it) under the seat failing to make contact (that was the cause of the same problem for some bloke on here recently)
etc. etc.
 
Need more evidence: I would get it idling and start waggling some wires to see if you can make it die.

Batteries (of the classic lead-acid variety) loose about 2 percent of charge per day (1percent if its a new GEL or AGM battery)
 
They don't like being fully discharged (ie - don't leave it for 3 months)
They REALLY hate having lots of current taken out of them when they're nearly discharged (ie - don't attempt to start the bike with a flat battery).
 
They also don't like being over-charged.
 
Problem is ,to treat it properly whether you have it on of off the bike you need either an optimate or similar (and beware imitations) or you need to understand the science of batteries.
 
Basically:
They DO like being float-charged at 13.8V.
If you let it go above 14.3 volts for more than a few hours it will die slowly.
If you let it drop below 11.8V for more than a few days it will die fast.
If you charge it with more than 1 amp it will die slowly (but that only applies if its nearly fully charged)
If you treat it properly it will last 10 years.
 
As an example ... My Ford Fiesta battery dates from 1998 and its still good.
 

If it helps any ... I have cooked mine until the warning light came on by leaving it idling in the garage for hours by mistake...
10 years later it still works..

You sure your 'miles' aren't kilometers? 
To get 300 miles out of a tank you'd have to lend it to Mother Theresa on a 30MPH mercy dash!
 
200 - 210 is more normal.

They use to hassle my 93 yr old uncle for not having a TV licence even though he didn't have a TV and could have got a license for free anyway.
 
They told him that to avoid harassment he should get his free license.
Problem was that having spent the last war inventing new and more efficient ways to kill Germans he wasn't about to play that game.
 
It was all a big game for him, no sooner had he reached agreement with one 'jobsworth' then a new and
more vicious 'enforcer would appear and ask to search his house for a TV.
 
He died in 2007 having never had a license.

My brake pads are the original 12 yr old item and they are NOT pish!
 
Brake pads seem to not like being kept damp.
 
How they work is a 'dark art' : It seems that they contain some soft brass or copper that smears against the Iron of the disc and creates friction when it drags against the 'filler' (which used to be asbestos but is now something that is less likely to kill you 40 years down the line).
The result is a black powder that contains Iron and copper: The black stuff that you keep having to clean off the front wheels on your car.
 
If they're kept wet, the surface tends to 'grow' (ie the pad gets thicker) and they turn green (if you look at them with a magnifying glass)
and your job is to wear it down below the "reacted layer".
 
A few 'hard stops' might well solve your problem.
 
 

Reckon it hit 75 fahrenheit

Who is this bloke "Farenheit" of which you speak ??
 
Petrol now six guineas, seven shillings and a groat per gallon in my village.

It was probably Harry Hewitt trying to avoid being Taleban-Target #1.
 
Next year he's taking up blindfold tight-rope walking without a pole!

I found a bag of skunk the other day and I can't smoke it ... I gave up smoking 25yrs ago..
The downside to giving up smoking.
 
I think I'll grind it up and bake a cake! 
 
 

do you not ride it?

 
I ride it on fine summer evenings to country pubs ... I gave up riding in the cold and wet 20 years ago    .
 
Anything below 5C is 'car time'... and modern computer generated weather forecasts mean that "getting wet" is punishment for not
doing your climate simulation properly before you go out.
 
Use NOAA (kindly funded by the American taxpayer and me!) ... http://ready.arl.noaa.gov/READYcmet.php
 
You need never get wet again!