2015 Summit X - Strange noise when revving at a certain RPM range

[Danstar10]

Last few rides of last season I noticed a strange noise when revving that seems to come in around mid rev range, maybe 5-6k rpm at a guess. It kinda sounds like a crackling noise, almost like a radiation geiger counter crackle.

I got it on video, its a little hard to hear over the normal rev of the engine and the wind but when you notice it it's pretty obvious. It is throughout the video but here are a few timestamps of when you can hear it to help locate the sound:

• (0:03) just as I pull off for a fraction of a second
• (0:17) - (0:18)
• (0:33) - (0:40)
• (0:50) - (0:51)
• (0:56) - (1:04)
• (1:22)
• (1:43) - (1:47) could be the easiest to notice here
• (2:00) - (2:04)
• (2:16) - (2:18)

I'm not sure if it is linked but I also found the last few rides it seemed to have some trouble revving to full 8000rpm. Sometimes it would get around 7900 which is all good but sometimes would top out around as low as 7300 or there abouts when pulling up a hill. I think but am not sure it is better at revving to full rpm at lower elevation but I am not certain that is correct. I tried changing spark plugs in case but that did not seem to help.

Any ideas what may be causing that weird noise / limited revving?

Cheers

 

[Lake Powell]

Possibly it's the rave valves not opening correctly at that rpm. When was the last time you cleaned them? Peter

 

[Danstar10]

I've never touched them but the top end of the engine was rebuilt a few seasons ago and I don't ride that much, I think I've put less than 1000km on since the rebuild.

Would dirty rave valves possibly be making that noise? Or is it that they could be restricting the rpm?

Any info on how to check / clean them myself would be appreciated. I've heard of rave valves but don't know much about them tbh

Cheers