To cut a long story short the bike was running poorly. Compression on the front pot very low. The rear has compression but nowhere near as good as my SS. After pulling the front pot off it became evident that the inlet valve was leaking like a sieve. A shot of carb cleaner disappearing almost as fast as I can squirt it in. Bike has previously had some kind of valve job. Notice enlarged valve pockets on the pistons
	Rubber valve guide seals are shot. Some of the shims have been ground down badly and one is wedge shaped! I don't know who did the previous work but the expression cowboy comes to mind! Any way things aren't terminal as the valves and seats can be reground / cut and everything reshimmed accordingly, not by me I hasten to add as I've no tools to carry out this type of work (as yet) plus its someone else's bike.
	The rear head was a lot better I originally pulled the front off but after seeing the state of that I thought the rear warranted a closer look. You can take the front off very easily ( takes longer to get the damm fairing off!) But to remove the rear you've got two options; either drop the entire engine out or you can remove the front and top engine bolts and let the engine rotate down. You still need to disconnect the chain, ignition and alternator wires to do this plus the ignition wiring gland that screws into the side case. With the help of a jack and some gentle manoeuvring the engine can be rotated enough the remove the rear head. But you need to watch those ignition wires!
	Well after a valve/ reshim job including recutting the valve seats every thing went back together easily apart from rotating the engine back upwards into the frame which is a bit tricky on your own. I set the carbs up with the aid of a carbtune gauge and thought all was well and the bike ran great. However the bike developed a tendency to go onto one cylinder at low revs after a while and was spitting back out of the front carb. Later the front pot died completely. I found that the plug had died ( strange I have had two virtually new plugs fail in one year) and a new one cured this only for the fault to return.The problem only occurs after leaving the bike ticking over for a while or running at very low speed. I did a plug chop at 90mph and everything looked great. After pondering about ignition, mixture settings and browsing the net and reading various articles. I think that its got to be a combination of mixture and modern fuel. So when I see the bike again in the spring, I'll try and get it running a bit leaner and at the same time raise the tickover which is supposed to help when you've got 40mm carbs. A bit of research I did on NGK sparkplugs seems to suggest that a number lower ( B6HS) should now be fitted. There is however definitely a problem with modern fuels ( just see what it does to your hands now!) I have read about various problems from plug fouling to 'going off'. I have experienced the latter on my old XR600 which would not start if the fuel was more than 3 months old. The most common themes on old bikes seem to be related to fouling and also the fuels ability to eat its way through various bits of the fuel system, fibreglass tanks seem to be particularly vulnerable!