Awful whirring noise on startup

Hello! My dad recently bought a crappy yx600 radian, and as it has the same engine as the xj600, I was hoping that I could be helped with a strange issue we’re having with it.
The bike runs like crap, but that’s just carb stuff, and not the main issue at the moment. What is weird is that whenI turn the bike on, after a few seconds and at a slightly higher rpm (approx. 1500), a loud whirring noise occurs suddenly. Sounds kinda like a corded drill under load. It really doesn’t sound good so I switch the bike off fast when it happens, making it so I can’t tune the carbs.
The noise is coming from the lh side of the bike for sure. It kinda sounds like the starter bring backdriven, but the noise only starts after a few seconds of running, not immediately. I pulled the starter to make sure it wasn’t fried and other than a lack of grease in the planetary gearset it was fine. Minimal brush wear, minimal bearing wear. Not really sure what to check next.
Thanks possibly in advance.

 

Does it sound similar this? Worn clutch hub bearing. My XJ900f sounded like this. My clutch hub bearing was the cause.

 

Nope, not quite that bad. I’ll get him to send me a video of it. Like I said, sounds like a big drill.

 

I'm going to guess it's most likely the starter clutch sticking "engaged" and over running the starter motor. Possibly wrong oil, dirty oil, or just from sitting for a long time. Change the oil and start and stop the motor a few times. You might get lucky and it will work itself free.

 

That makes a lot of sense. Do you know how the starter clutch works? I can’t find much info on it. I did put fresh oil in the bike, maybe it made it unhappy somehow.

 

Starter clutch works like this.

 

Add Seafoam to the oil (per instructions on the can) as a first step in fixing that issue. Oftentimes a lack of regular oil changes will cause sludge to form which then makes things like the starter clutch become stuck in one position.

 

Started up the bike this morning, just to continue troubleshooting. Thing is, today it started right up. No carb issues, it literally just woke up and ran perfect. I had been adjusting the throttle collective screw to get it to run when it was running poorly, and I guess I had given it too much, because it started to rev up pretty fast. I killed it and adjusted the throttle screw out some, and turned it back on. Still ran great, and it had no starter sounds. It didn't like me giving it any throttle, seemed to want to die as soon as I touched it. I then realized that the fuel and petcock vacuum line had been left disconnected, so I shut the bike off and hooked them up. Bike still ran great, and now that the vacuum was hooked up I could give it throttle.
For a few seconds. It then started dying again, and when it was running poorly it started making the noise again.
I'm really not sure what's going on here. There was no starter noise and the bike was running better than ever, right up until the bowls started filling with fuel again. Maybe the float level is absolutely cooked or something and that's making the bike run poorly, but I don't know why the bike running poorly would cause the starter clutch to grab.

 

Haven't heard that noise before.

 

Sounds like the starter is still rotating ---- either the solenoid is bad and is still passing current to the starter motor (even after you let go of the START button) or there is something really, really wrong with the starter clutch....

 

Hmmm, if you pull the plugs and push the bike in a low gear you should hear the starter spinning if the starter clutch is locked?
Worth looking in the generator just in case?

 

Right, but the thing is, it didn't do it the couple of times the bike ran well yesterday, and started doing it again as soon as the bike was running like crap. Bike only started running like crap when I hooked up the fuel tank; it had been sitting for a week prior to me starting it yesterday, I imagine the fuel level had dropped in the bowls. I'm gonna see if I can make myself a little fuel level checker, see how off it is, cause that's really the only clue I have right now.

 

Alternator shaft bearing? Put a screwdriver or mechanics stethoscope on the alternator housing and the starter motor housing to check the noise.

 

To my ear the sound is coming right from the starter. I’d remove the small wire plug from the starter solenoid to isolate it from the starter button, and use a coin to jump the solenoid (taking it out of the equation as well) if the starter stops making the noise and it doesn’t come back after several starting cycles, then the starter isn’t the problem. At that point you can start checking for continuity at each of the parts of the starting circuit to see what’s stuck (the solenoid, or the starter switch). That it didn’t happen with the tank off makes me think it might be due to a pinched wire causing a short to the frame.

It’s an intermittent problem, and will take some time to diagnose properly.

 

Checked my float level (kinda) with some clear plastic tubing and a yellow wiring butt connector. LH side seems alright, but the RH carbs are literally over the top.

Good idea, I'll give it a try once I get the carbs back on (currently setting fuel level on a bench). I doubt that the starter is doing the driving here, as it does sound like it shuts off after I release the starter button, and then starts winding up afterwards.

 

I'm still really not sure what causes it to make the noise. I've gotten the bike running better, so now when I fire it up it never makes the sound. Now that I actually seem to have functioning carbs and the bike isn't tearing itself to pieces when I try and start it, I'm onto my next problem- it tries to run away on idle. I'm not sure if I should start a new thread for this, so it goes here for now. The bike seems to be running overly rich. I had to set the idle needles as I took them out to clean them, and now the bike starts cold and runs fine without choke. I haven't gotten it to run long enough to properly warm up yet because after I start it, it likes to start revving up after 45 seconds- 1 minute. I'm not sure if this is a balancing issue causing the bike to start running away, or if it's just so rich that it's doing strange things. I currently have the stock idle jets and screws in the bike, with the screws set 2.5 full turns out from being bottomed out. Unless I'm mistaken, that seems to be the correct base setting for these bikes.

 

After some more testing, it appears that the bike runs with the idle screws all the way in. Choke still kills the bike, so it's not like its running off of that. I guess that somehow it's taking fuel from the main jet and running off of that, and then using that to run away. All four pipes are equally hot, and it runs smoothly, so it seems all four carbs might be doing the same thing.

 

Turned out that the revving up was caused by an overly screwed in idle adjust screw, my own fault. It was just so screwed in that I didn't even consider it, as backing it off seemed to make no difference. The carbs are still seemingly running off of either the main jets or the idle jets on idle though, as with the idle screws bottomed out it's still so rich I can hardly give it any choke, plus the exhaust stinks of fuel. I did take the carbs down to the basic bits to get them cleaned out, including removing the emulsion tubes for the main jets. I didn't see or replace any o rings in here, but maybe there was one or was meant to be one which is now leaking gas into the intake.
Fuel level is still great, sitting a couple mm below the carb body, as per manual spec, so I don't imagine that would be an issue.