Still missing

[Lonerbtw]

  I still have a miss and back fire on the left side. Changed the lines. That helped but still there. Went after it again with carb spray. Could not find anything on the carb banks. But when I got around the petcock the RPMs went up again. Checked the line from #6 and looked good and was on tight. Is there any place on the petcock that would draw a vacume besides that vac line? Can I plug #6 line and run a line from #5 to check if the back fire goes to the right side? How bad of a problem do I have if I just ride it? It cruises really nice after I get into 4th gear but sounds like a race car when I back down.

[Farther]

Why not replace the vacuum line?

[Daniel Meyer]

Sounds like the petcock may be blown.

Pull a vacuum on it...it should not leak down at all. If it does, it needs rebuilt.

[Patrick]

Yep, it certainly sounds like a defective petcock diaphram.. You can hook the petcock to any intake tube your little heart desires, it doesn't care where it gets its vacuum from.. If the miss-fire goes to that other cylinder, you're right, the petcock is the culprit.. You can then fix the petcock or just install an aftermarket[ like a Pingle] and never worry about it again..

[Lonerbtw]

Pluged #6 , pulled vacume from #5. Used new vacume line. Still have miss and backfire on left side. Can still spray petcock and increese rpms. Pulled a vacume on petcock and it held for 5 min.

[Red Diamond]

If all's well with the vacuum lines and you have taken care of all the vac leaks, make sure you don't have a spark leak from a spark plug wire. It is hard to see in the day, but you can start it up in the dark. If your wires are failing and grounding out to nearby metal, you can see it.

[3W-lonerider]

if your spraying the petcock with the engine running and the gas tank on the bike..which i assume you would be..the air intake to the airbox isn't very far from the petcock..i would assume the airbox is sucking in the spray and affecting your rpm's. i'm with the rest of the group..i'd seriously check the spark plugs..and check to see if there isn't some water laying at the bottom of one of your holes..

[1fastbob]

My bet is on plugged or partially plugged slow speed jet.  I would think that possibly when spraying the carb cleaner around the petcock some of the vapors are getting into the air box and causing the engine to run differently. Before I'd pull the carbs I would run a compression test on all cylinders to made certain that you do not have a slightly bent valve or other issue at the cylinders.  Also make sure the battery is good and the battery connections are tight.  Loose connections at the battery can cause some odd problems on these bikes.

Just my 2 cents

Bob

[Patrick]

While the engine is running, pinch off the petcock vacuum line and see what happens.. That'll let you know if you have a bad diaphram..  I'm kinda leaning toward a bad diaphram or a plugged/varnished low jet..