1100 Yamaha Backfires and won't start.

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Dystopian · #1 Unread post by **Dystopian** » Wed Dec 21, 2011 6:30 pm

I've been working on this bike for a while now and I can't seem to get it working.

It's an'79 1100 XS. It would run before, but fuel would pour out of the run-off hoses, I forgot the actual name for them. I freed 2 of the floats and I could get it to run, but only 2 (Or maybe 3) cylinders would fire. The left cylinder was cool to the touch while the other were at operating temp. I took them out, cleaned them and put them back in.

Now it won't start, it just backfires constantly and sometimes I'll get some pressure shooting out of the vacuum hose for the right pet-stick. I drained the fuel tank because it's got old fuel in it, but that doesn't seem like it's the only problem here.

Any help would be much appreciated.

#2 Unread post by **Wrider** » Wed Dec 21, 2011 8:28 pm

Did you mess with the valves at all? It sounds like they're timed backwards.

Dystopian · #3 Unread post by **Dystopian** » Wed Dec 21, 2011 8:32 pm

Nope, I haven't touched anything, and it ran perfectly fine when it ran last...a year ago.

Johnj · #4 Unread post by **Johnj** » Fri Dec 23, 2011 4:47 am

STOP Now start over like you just assembled it, and check everything. Some thing is backwards. I think it's the coils. but I'm an electrical guy

Dystopian · #5 Unread post by **Dystopian** » Mon Mar 12, 2012 6:10 pm

Sorry about the delay, but the weather's finally permitted me to work on it.

So, it turns out I mixed the wires for plugs 3 and 4. Now it runs again. I also found out at some point I flipped the fuel filter around, so now it's facing the right direction.
I took the carbs off, took out the floats, then the jets, then I removed the threaded...things the jets sit inside. I cleaned those off, cleaned out the little screens, cleaned out the inside of the fuel intake and re-assembled. It seems like the 1st cylinder started to run, but the pipes for 1 and 2 were only slightly hot, not enough to burn.
I ran out of gas so I'll try again in the morning.

EDIT: I got cylinder 1 to warm up slightly. By the time 3 and 4 were melt-your-skin-off hot, 1 was still only slightly hot. 2 has seen no progress. I can't figure out what the problem is. I can't find anything that's blocking the fuel.
I should note that after running for a bit, when I take the carbs off, 3 and 4 smoke, but 1 and 2 do nothing.

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1100 Yamaha Backfires and won't start.

1100 Yamaha Backfires and won't start.

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