Engine noise

[bwe421]

i adjusted cam chain tensioner, adjusted valves, and set gaps and timing on the points...fired her up! sounds great! although...i hear this "scratching" noise when i rev the engine. let me know if you can hear it at about the 12second - 15 second mark in this clip. advice appreciated! note: i have not tuned the carbs the yet. they are cleaned and rebuilt but i havent synced them yet. thanks in advance!

https://drive.google.com/file/d/1gaIJA9Ic-qcKzktg5iC-Nmuhnjzp8bYm/view?usp=drivesdk

 

[Jan_P]

No I cannot hear it .. It sounds unusually quiet from valves and so are those within spec ?
But the sound can bounce when indoors but I cant hear it .
Maybe you know about holding a screwdriver between places on the engine and the ear or a steel rod
Outdoor recording ?

 

[bwe421]

valves are .006 and .003. hmmm no i dont know about the screwdriver trick. the scratching noise happens like right at the 13second and 14second mark...almost sounds like a super loud ratchet. i can text the video too if anyone is interested

 

[Jan_P]

The ratchet sound i can hear as 2 sets ;but it sounds as a Shooting in the exhaust

 

[bwe421]

The ratchet sound i can hear as 2 sets ;but it sounds as a Shooting in the exhaust

yep exactly! to be more specific after further investigation...the scratching noise happens when i roll off the throttle...not while and sounds like shooting from exhaust

 

[gggGary]

yeah like Jan sez decel backfire/burble, normal with "straight" pipes.

 

[bwe421]

sheesh there is decel pop and there is this! ok thanks for the input, gents. just wanted to make sure it wasnt a more serious issue. i wonder if anyone else out there with these pipes has/had the same noise

 

[gggGary]

The cheap seats version but;
An XS650 motor has a lot of valve overlap, on decel with no exhaust restriction before the exhaust valve can close for compression the pipe will pull some raw mix from the intake/valve right out into the exhaust without that annoying squeeze bang in the way. The next time the exhaust valve opens it lights that raw mix.
Why race motors with radical valve timing sound like that also.

 

[bwe421]

ahhh interesting. ive just never heard decel pop sounds like this but that explanation makes sense. Thank you!

 

[Raymond]

Yeah, that's the classic BAAH! you get when you rev a Norton Commando. I recall years ago when I had a Commando, my pal pointed out to me that it went VROOMBAAAH! - the vroom as you open the throttle and the baah as you shut it down. Nuffin to worry about IMHO.

 

[bwe421]

excellent! love the sound of a nice idle in the morning. first time starting in 20yrs always feels good. idles fine when fuel enrichner open and bogs down when i close it so still some tweaking to do with the carbs but its sounding good!

https://drive.google.com/file/d/1VzotVsBN9Us_UzI1qXVF_DRyj63iSLTR/view?usp=drivesdk

 

[Jim]

Stock mufflers with holes drilled in the end caps. Personally.... I love the decel sound. Sounds like a race bike. Doesn't act like a race bike... but lets not talk about that...

 

[bwe421]

yeah those sound amazing. music to my ears!

 

[Grimly]

Stock mufflers with holes drilled in the end caps. Personally.... I love the decel sound. Sounds like a race bike. Doesn't act like a race bike... but lets not talk about that...

During the exhaust noise, the subtitles are coming up "music".