Serious performance issues

So I realize this might be in the wrong sub-category, seeing as the problem could potentially be anything.. but this seemed like the best bet so here we go.

I finally got my '79 KZ650 running, but it isnt pretty. The only good thing is even on a cold engine it always starts on the first kick, so I got that going for me. But the problem is it has a very poor idle and practically no low-end power. I barely got it home from todays test drive, it was sputtering pitifully uphill. However it seems to be fine when I give it some throttle (over 6-7k). I took a video to show you how the idle sounds but unfortunately my camera's mic is junk, but you can at least see the RPM's jump on the gauge:

video: s284.photobucket.com/user/who8myrice17/media/MVI_1153.mp4.html

I've ruled out a carb vacuum leak and I've cleaned the carbs twice as well as installed all new pilot jets. All 4 plugs have spark. New battery and new plugs. Maybe its a timing problem..? A carb sync problem? both? I should mention it also backfires quite a bit and the exhaust has a strange gas smell to it but all 4 headers are getting hot so I think all 4 cylinders are firing.

I'd really appreciate any input at all, thanks guy!

Also if it means anything, the #2 carb doesnt seem to be giving the petcock any vacuum- I have to leave it set to "prime" or else it just runs out of gas.

I'd check the valve lash first.

After that, I'd be looking at carbs - but mostly because that's what I expect to be bad.

Timing and dwell are easy. Coils measurements are too. Those next.

Fuel tank crud next. R/R your petcock, rinse out the tank with rubbing alcohol, install an inline fuel line.

Let us know what you find.

I'd also check valves first, then timing and sync the carbs. make sure your pilots are the correct size for the application and that the fuel mix is dialed in. this is old hat, but check the voltage at the coils and make sure its around 12. if not do the relay bypass mod that many of us have done.

Would assure that the vac hose -- not vent hose -- is attached to petcock.

Would also perform clear tube tests to assure fuel levels being within specs.

And also assure that the ignition timing advancer is functioning properly.

Good Fortune!

Thanks guys, I'm going to adjust the valves and get the carbs synced and then go from there. The vac hose is definitely hooked up to the petcock. In fact both of the vent ports are blocked off, is this normal?

who8myrice wrote: Thanks guys, I'm going to adjust the valves and get the carbs synced and then go from there. The vac hose is definitely hooked up to the petcock. In fact both of the vent ports are blocked off, is this normal?

No, the vent ports must be open to the atmosphere so no pressure or vacuum builds up inside the carb bowls as fuel enters the bowls and is drawn from them. Ed

Does it run better when you turn the "choke" on? If it has been sitting I bet the carbs are still clogged up.
Also swap out those plastic banjo washers on your front master cylinder to the correct ones. The ones on there are going to leak.

Yes, it does seem to run a bit better with the choke on which points to a fuel problem.

Stupid question, but my carbs have the air adjust screws and I've been wondering when they are screwed all the way in is that the leanest mix or the richest mix possible? Thanks.

Turning the air screws in closes off air and makes the mix richer. Ed

I took another look at it today and the valves all seem to be within spec. I havent synced the carbs yet but I really dont think thats my issue. I wanted to run some seafoam through the crankcase to do an oil change so I started it up and let it idle for 7-8 minutes. It sounded fantastic at first, throttle was very responsive, no backfiring, etc., but around the 8th minute it suddenly started bogging very quickly and if I didnt give it gas it would just shut off. Giving it some throttle made it idle OK again for about 2 seconds and then it would start to bog again. At this point it also backfired somewhat violently when throttle was applied.

Im at a total loss here.. could it be the coils? I've heard heat can cause issues with the ignition system. Any other ideas?