TOPIC:

I just had my top end apart to put in new head gasket because of low compression. Before bike ran with little noise and all cylinders pipes were equally hot. Now immediately after I started it, there is a loud knock, and cylinder 4 is completely cold. I have spark, fuel, and equal compression. I was sure I put everything back together right, along with proper valve clearances. I did over torque head nuts just by 5 lbs since I installed the APE studs and nuts. Going to pull valve cover and check my valve clearances one more time. My only guess is valve issues. Help!

Sounds like a bent valve,
If so your valve clearance must be extremely high, because the valve can not close completely anymore.

That's what I was thinking. Even though all my tolerances were good and double checked with engine rotation. This bike has just been a pain. Never had issues working on anything like this bike until this. I'll be pulling the head and hope the short idle run time didn't mess anything else up. Hopefully it didn't bend a valve either, so I don't have to do a whole valve job. Sunk enough money into this already.

I wouldn't think the cylinder studs from APE went to far down into the crankcase. Torqued 4 center studs to 18 ft lbs and rest to 12 ft lbs. Seemed like they went down into the crankcase further than stock ones would be. But looked like right amount of thread left for stud nuts. Really thinking somehow my valve clearances got thrown off and it's a valve hitting and staying open on 4. Noise sounds like top end anyways.

I would first do a compression test to see if you have lower compression in that cylinder before you tear it apart.
You would be suprised how sometimes just removing the carbs from the bike for days can lead to stuck/open floats or clogged passages that will lead to a no run situation when reattached to the bike. I had a set of carbs that turned out to have all the fuel inlet passages clogged with rust. They worked fine until I removed them and then put them back on. It ran on three cylinders until I COMPLETLY stripped the carbs and found the rust hiding in them.
The loud clunking is more than likely from the imbalance of only running on three cylinders rather than something hitting. Running on three cylinders (and even just unsynced carbs) causes the primary chain and drivetrain to clunk like they are full of rocks.

I also had to put ball bearings into the stud holes to keep my APE hd from screwing in to far.

Don't think I'd pull the head yet as a few others have stated...... checking the valves should tell you if you have a bent valve and also you said the comp is good to right? .... you'll end up with double the gap (or so) you had before if that has happened and your comp will be very low ...... Also like rusty said a dead cyl will cause a lot of noise in the motor .... would be nice if its just a carb problem and am Hoping for ya its just that. Maybe a little gas in #4 to see if it would fire temp ??

Thinking clogged pilot and carbs way out of sync. Did you bench sync them?
Steve

I just remembered that the carbs you have, use a plastic plug that covers up the idle/pilot jet. If that plug falls out, the idle circuit gets flooded with fuel and will flood that cylinder out.
My bike had those carbs on it when I bought it and it also ran on only three cylinders. When I took the carbs apart one of the plugs was sitting at the bottom of the fuel bowl. They are made of plastic and may possibly use an o-ring, but most are brittle and poorly fitting which leads to them falling out when the carbs are jostled around.
It's worth taking a look.

I have even compression now in all cylinders at about 125 psi for a 27k bike. So that's fixed. I put new o rings on the plugs that were loose in the carbs, completely cleaned the carbs besides the pilot jets that has that cap over them. So going to order new aluminum plugs for the pilots, I have o rings for them already. I did a bench sync. My vacuum on gauges 2 and 3 carbs were not pulling but 1 lbs of vacuum, so that is weird I think? (4 gauge set for each carb). Just pulled my cams again, which are timed right, but before I pulled them I checked all clearances, and I had them all matched at .13 mm. So think my valves, cams, chain are all good. Float boal fuel levels in all carbs are perfect. So it just has to be a pilot jet, or plug cap or wire, checked once already had double spark on all plugs and the same amount of spark. Has to be a carb issue I am guessing like you guys are leaning towards.

P.s., is there a way to salvage the aluminum plugs for the pilots? This thing still has me stumped. Just has to be a number 4 carb issue or spark fault.

This is not meant to insult....but we are not there and can't see, so I have to ask. Are the coils hooked up correctly?
One coil provides spark to #1 & #4.
The other #2 & #3.
These coils are waste spark type, so they fire during the ignition and exhaust stroke. So if they are hooked up to the wrong cylinders, the engine can and will run, but like total crap and usually on two or three cylinders.
(Don't ask me how I know that..)

Are you referring to the aluminum block off plugs for the idle/pilot adjustment screws?? You will never need to re-install them, and if you do, you will more than likely need to remove them again in the near future.

Coils only bolt to designated sides on bike, I checked. And I will make sure wires are going to the correct plugs. Sure I did this right also, but will make sure as I'm putting everything back together. And thanks for the information on not needing to re install pilots plugs. I will keep everyone updated. Probably within a couple hours.