Buzzing Noise From Scrambler 400x

Hi all. I'm new here so but I hope you won't mind me leaping straight in with a technical question. I did introduce myself first in the Newbies Hangout so I hope I'm not jumping the gun

I bought a new Scrambler 400x back in January of this year. There have been several niggling issues with the bike but the most frustrating is an unusual and unpleasant buzzing sound coming from the engine. It's particularly noticeable at ~4,000 RPM in any gear while the bike is in motion. A recording can be found at the link below (turn up the volume and preferably use headphones):

Buzzing 400x engine noise

I've checked, re-seated, secured, padded or temporarily removed just about anything on the bike that has the potential to vibrate. I strongly suspect it's a cam chain/tensioner issue, but I would be very happy to be wrong on this if anyone can offer a logical alternative diagnosis.

The recording was made while doing ~40km/h in third gear (~4,000 RPM) and the fault is very repeatable as you pass through, or sit on that rev range, particularly when the bike has warmed up. The noise becomes increasingly obvious on longer rides. Aside from the regular engine sound, there's a distinct 'buzzing' like an angry wasp inside a tin can. Its quite loud and rather embarrassing.

This was reported to the Triumph dealer soon after purchase. The service department at the dealer in question (there's only one Triumph dealer in Adelaide ) kindly checked the bike over but somewhat staggeringly, the mechanic reported hearing nothing out of the ordinary. Having been reassured and sent on my way, I had hoped the annoying engine noise would diminish once the engine bedded in a bit. Sadly, the noise remains after 3000 km+

The dealer is aware of the problem but has yet to agree to do anything about it. I'm new to Triumph, and a relatively new rider. I wondered if anyone has experienced something similar.

Any advice would be very welcome.

 

Thanks for the suggestion. I had come across that video previously and followed the advice to put a bit of padding behind the Triumph badge. I've padded a lot of other parts that I thought might have the potential to vibrate too. Unfortunately, the irritating sound remains.

I'm sorry to hear you got that unhelpful response from the dealer. With those psychology and personal skills, he could perhaps consider a career in politics

Yes, I certainly will be doing that. However, last time I did they insisted that they couldn't hear anything out of the ordinary

 

Thanks ajc400. Hehe yes, comparing anyone to a politician is probably being a little too harsh so I apologise to the dealer in question.

Interestingly, and pretty much echoing your suggestion above, someone pointed me to the 400 forum and a discussion about the rear suspension spring vibrating and making a loud buzzing noise at 4,000 RPM in any gear. I'm going to do some tests over the weekend to see if that could be the problem. I'll be so very happy if it turns out to be something so simple. I'll let you know what I find.

 

Yes, mate. Check this thread on the 400 Forum. The results of the testing performed by me and others are documented there.

The short version of the story is that vibration (sympathetic harmonic resonance) seems to be the cause of the annoying noise. Interestingly, this effect is intimately tied to load on the shock spring (~rider weight) as I've demonstrated in that thread. So, a lighter rider may report hearing nothing out of the ordinary when they test the bike!

I've got the bike booked in with the dealer's Service Dept. for Monday. I've asked them to try swapping over the shock. I've ridden other 400's from there in the past and they didn't exhibit this noise issue. Any change (or hopefully) elimination of the noise will demonstrate conclusively that the rear shock is the problem. Maybe a better quality, third party suspension solution is the ultimate answer.

They're also updating the ECU to see if that eliminates the stalling issue but that's another story.

 

Hehe, Thanks for the suggestion. I've tried padding, tightening, lubricating or temporarily removing just about everything easily accessible on the bike The infernal noise remains I think it might be coming from somewhere near the top of the shock or up under the fuel tank maybe(?). I haven't pulled all of that apart (yet) so you're probably right.

 

Delete please