Loud rattle after work done - Is it the Big Twin Neutral Rattle?
 

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I took a few things apart to do a couple different jobs, and when I got it back together and started the bike there's a new noise that wasn't there before. I was hoping something in this sounds familiar to someone who could help me figure out what to read up on to start figuring this out. The noise is very loud, and sounds like bare metal surfaces clanging together in a confined space. It doesn't really have a discernible pattern, it's persistent but random at idle.

Here's what I did that lead up to this. I had the exhaust off because the powder-coating on it is failing and I was going to deal with that. While it was off I took the opportunity to do a big detail and degreasing job on the motor. To keep out water I plugged the breather holes with normal bolts, but forgot they were in there when I was done. I started the bike and noticed the rattle immediately and then 30 seconds later realized the plugs were still in. There was a bit of air pressure in the front head that hissed when I removed the bolt. I reinstalled the AC back-plate and the breather bolts, and started the bike. Same noise, no change.

Going back to when things were apart, another thing I was working on was the clutch cable. I had removed it from the lever and laid it down on the floor in order to measure it, and it sat like that overnight. The next day there was a bit of oil pooled around the adjuster nut. I figured it had dripped down the cable slowly overnight. Bike was on the side stand during this part. I may have done something wrong during the process of putting it back onto the lever and unseated the balls from the ramp. Since I had only taken the lever end off, I thought I was going to be okay to just do the adjustment on the cable and get away with not doing the other end as well. I may have actuated the lever when you're not supposed to and caused the balls to unseat but I'm not exactly sure about that. So I did my adjustment for lever freeplay at the adjuster nut and tried again. Same noise, no change.

I should add that the main project here was to install my new PowerVision tuner with Target Tune system. Other than making the engine sound fantastic I don't think it has anything to do with this, but I will mention it for completeness.

Here's what I found for clues: I used a trick I learned on here to hold a screwdriver handle to your skull/ear and the other end to the bike and it works really well to isolate the source of vibrations/noise. I also used a paper cone in my ear to do the same. Both of these made me think the noise is coming from the clutch basket more than anywhere else. The noise happens in neutral at idle only, and is very loud. The motor sounds exactly right when revved up, and the rattle goes away. Putting the bike in first and idling with the clutch pulled in also stops the noise.

What is it that causes the balls to unseat? If I remove the cover to get at the engine-end of the clutch cable, can I reuse that gasket or does it need to be replaced every time? I'd like to install my new cable since it showed up sooner than expected, but a new gasket will be a week to get I'm sure. If this is the Big Twin Neutral Rattle that I'm reading about, is it only showing up now because my PV is somehow running the engine so well that it's now being revealed? I've never heard this rattle before today.

Thanks for any comments or suggestions about any of this. If I did something stupid, I'd be grateful to hear that as well.

If you un-seated the balls you would have no clutch at all so I think your ok there. As for the noise hard to tell, maybe post a video clip...but if it’s in the clutch area you would be wise to pull the primary and have a smell and look.

Okay that helps, thanks. Clutch seems to work properly so that makes sense. I let the bike cool overnight so I could do the adjustment first thing today. I'd really like to get the new cable on there, but if I take that cover off and the gasket isn't reusable, I'm going to miss the first batch of nice weather I've been able to get this year, so I'm probably not going to. After I do that, I'll start it up again and get a video of the noise.

Reading last night has me thinking this might be related to the primary chain tensioner. It would explain the quality of the sound itself: metal on metal slapping inside a confined space that gives it a sort of echo. I don't understand why that would be fine previously, and show up exactly when I put the tuner on. Maybe there is a new idle speed that somehow reveals it? I'll call Fuel Moto to see what they say. I have a BUSErr (Bus Error) code that comes up on my LCD tacho when I turn the key on since I installed my PV/TT. No mention of it in any FAQ or forum post that I could find just yet.

I had a local shop do the forwards to mid conversion, which involved swapping the outer primary cover. Maybe this is related to that? Maybe something wasn't torqued or whatever and now it's showing up? Again it's strange that it happened exactly when I put the new tuner on, and not in the last ~5,000km that I've driven without this issue. They didn't put my exhaust back on properly which caused me to have to replace a long trans cover bolt whose threads were gacked by the bracket. Maybe some gremlins snuck inside the little gap in the cover while I wasn't looking.

For me, a loud metal on metal sound means the bike isn't safe to ride. I would not risk destroying my bike because I was in a hurry to ride.

This would seem to indicate that the main shaft of the transmission has to be spinning to make the noise. Any chance there's a spare nut rattling around in the bottom of the primary case? Since (I think) you had the clutch cable out, that's where I'd look.

Symptoms of the inner primary bearing being bad...noise goes away with the clutch pulled in. Only way you'll find out is to start pulling covers off...unless you want to wait till it's completely obvious what was wrong lol. That way tends to be more expensive and ties the bike up even longer.

Here is how to determine if a sound is a failing inner primary bearing.

With engine running, transmission in neutral, clutch lever released, you will hear the sound,

Pull int clutch lever, you will still hear the sound.

Drop transmission into gear, the sound stops (when you drop it into gear, the mainshaft stops spinning).