I broke my Yamaha

[BlaRo]

Yep, the Yammy has a vacuum petcock. And I'm running into the same problems I had before when I bought the bike in the beginning.

[Spectre]

Okay... if you put it into Reserve, does fuel come out of the petcock?

[BlaRo]

So I started the bike up yesterday, and after adding fuel and a freshly charged battery and cranking it over for 5 whole minutes I can say that it does run...albeit very badly. I have to apply the choke or it dies completely, the valves are louder than ever, there's still that low booming whump-whump-whump sound emanating from the bottom, and there's a small of burning oil or powder that just sucks the air out of my nostrils.

My friend (who's pretty knowledgeable, if I may add - he's been helping me get my Honda running and painting the tank properly as well) said it sounded like a timing issue, and that the timing jumped when I stalled out. If that was the case I would have to disassemble the top end to replace the cam chain and tensioner, and take off the cylinder head and check the valves for bending or damage.

However, I talked to a guy at a trustworthy bike shop today and he said I should check my jets for a clog, because a timing issue sounds more unlikely on a new-ish bike with a chain tensioner like mine. So I disassembled one carburetor and all the jets were fine, haven't gotten around to the other ones, noticed when I removed my carburetors that the airbox had been barely attached to the bike, and suspected that may have been part of the problem.

Well, I've just reassembled the fucking thing and it didn't fire up, so I figure it's just as bad as before. So I'm going to let it sit and take it to a shop in November when I'm home from break. In the meanwhile, I'll get the fairing painted and repaired; if I do sell the bike for parts (unlikely, but I'm not ruling out anything at this stage) I can get rid of the fairing at a good price considering how rare they are.

[hansvonaxion]

I had a similar sounding problem with a bent valve or two - it ran, barely, really rough, somewhat like how you're describing. If I remember correctly your bike may have over-revved, which could have bent valves like was already said. Is your friend talking about valve timing? (usually "timing" refers to ignition)

But mechanical problems are best solved via process of elimination rather than guesswork over the internet.

Good luck with it.