Need troubleshooting help! Upstate, SC

[lethal dose]

Food, etc. on me. Having a problem with the #3 cylinder. Possibly a valve issue?

 

[davesax36]

Got a video of the problem? What's it doing?


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[lethal dose]

I sent my carbs to Danny last week (DANG they're clean!)... I cleaned them three times with tons of carb cleaner and compressed air. Still had this odd random pop through the right exhaust (why I sent then to Danny). Got the carbs back today, put them on, sync'd em up, etc. The pop seems mostly gone (maybe an occasional one) but at idle, the left exhaust sounds even and consistent. The right seems to have a random skip... almost big cam like. It smooths out a smidge if I back the mix screw on carb #3 out 6 turns (the rest are at 3) but isn't perfect. I checked spark on all wires and it seems good. If I shut that mix screw all the way down and run it on the front cylinder, it's nice and smooth. Once I bring the problem cylinder back up, it gets erratic (no rpm fluctuation, just a erratic idle).

So... I have gas, air, good consistent spark, etc.

I'm thinking vacuum leak and have been told it could be a valve. I'm terrible at tracing vacuum leaks (tried starter fluid) and am not up to tackling valves alone (not wanting to pay a shop for 2,000 hours of labor, either).

I was thinking a nice afternoon of vmaxer fellowship, spinnin' wrenches, etc. would be cool!

 

[Dragmaxster]

Pull the 2 plugs on that side and give a description of the colors.

 

[Dragmaxster]

Twist the plug wires tightly into the boots and coils.

 

[lethal dose]

I trimmed 1/4 inch off all plug wires and reattached. Nice and tan on all plugs. Replaced all four today.

 

[Fire-medic]

Any nasty green corrosion on the plug wire ends? Plug caps are inexpensive. I don't think it makes any difference if you use resistor or non-resistor.

Has there been some discussion about using a DYNA 3000 and non-resistor caps on the early '85-'89 ignition? That's about the only thing I can recall which may be an issue for some people. Since these two bikes have the newer ignition, this shouldn't be an issue here.

I trimmed 1/4 inch off all plug wires and reattached. Nice and tan on all plugs. Replaced all four today.

 

[lethal dose]

No corrosion. Are there any plug caps available at the local auto parts store? I know ngk makes some.

 

[Dragmaxster]

Vacuum leaks are as easy as spraying fluid at the intakes and listening for rising rpm's- no big deal. If you run that a/f mixture screw all the way in or "6" turns out then you are way out.Put it back to where dannymax set it. Do you have a carb sync.
I am sure he set them to his test motor and now you need to set them to your motor.
a/f mixture first then sync.

 

[lethal dose]

Already done. Check 3rd sentence on my op. It's taking sync great! It's the strangest thing ever.

 

[Dragmaxster]

Already done. Check 3rd sentence on my op. It's taking sync great! It's the strangest thing ever.

I only saw one line on your op?:confused2:

 

[lethal dose]

HA! Second post.

 

[Miles Long]

NOT an engine guy, by anyone's standards - but if you suspect bad valve(s), and assuming spark and fuel are good to all four - wouldn't the next logical steps be compression and leakdown tests:ummm:
Wish I was close enough to attend the wrenching. Always eager to learn!
Cheers!

 

[lethal dose]

Already on the list. Gonna check compression tomorrow!

 

[Dragmaxster]

Already on the list. Gonna check compression tomorrow!

Let's hope it's not--
Check the other end of the plug wires too as they will vibrate loose- although the ends screw in some do not have the donuts around the wire to help tighten them enough.

 

[lethal dose]

Will do. Only thing is... spark is 100% consistent.

 

[Dragmaxster]

If it is a valve out of adjustment you will usually see a different color on that plug. You say they all look the same- worn valve seals will show black oil on the plug, and white could also be worn cam lobes.
Below is for a 4 cylinder car engine but the order of the misfire is what is helpful.
http://www.obdii.com/articles/Diagnosing_Misfires.html

 

[lethal dose]

I wouldn't say there's a specific order to it. Perhaps it's not even a misfire. Gonna try to recheck for vac leak. Try, that is. Haha

 

[lethal dose]

Judging by the sound, I'd say this wouldn't be a valve adjustment issue... More of one not functioning.

 

[lethal dose]

If there was a vac leak, would that show while syncing or not always? Carbs did sync up.