Peculiar low rpm sound, please listen

[Uladimir]

Hello

My '85 GS 400 is making this sound, only happens under 2000 rpms, any speed, clutch or not, braking or not.

I have an old build thread with details, but harness, plugs and boots are new, I cleaned the cards with new o rings, have so far checked the exhaust connection at the outtatke off the head and checked carb boots for air leaks. I did valve clearance at the beginning of this season and did very few km this summer. It seems rpms drop off slightly when the clicking occurs, it seemed electrical to me so I cleaned and re attached the connections at my coils, no noticeable change. Good voltage at coild and I have the coil relay mod.

https://youtu.be/ElnFq70bwTQ

I appreciate your insights

Merry Christmas!

 

[Steve]

Well, I will have to admire your phone for its ability to filter out extra noises, that sounded pretty much like a normal twin to me.

One thing the recording DID show, though, was that you need to do some more fine tuning so the engine keeps running. If that was a cold engine, the "choke" is not set up quite right. If it was a warm engine, either the pilot mixture or the idle speed is off.

.

 

[jsandidge]

Get a mechanic stethoscope. I poked around with one and found my clicking noise at the tach drive. Seems like the driven gear has a little too much end play.

 

[Gorminrider]

Exactly As steve and jsandige said... the bike should idle by itself. That's the obvious fault from video, not tappet noise.

if it won't idle low, beyond tweaking the enricher/"choke" and throttle set-up, I'll offer a curve ball that I've experienced with my 400s. these bikes can sound suprisingly "ok" on one cylinder.

Check that both cylinders are firing: FROM COLD START- Hold your hand near the pipes to ensure both are heating up together....(if you wait too long, they will both be hot even if one side is not firing as heat travels through engine) Obviously this is not good for the bike but you can even go down the road with the mere 200cc but the disappointment is strikingly obvious because it dies at stops without working the throttle hard... It's Plug won't even foul if there's no fuel or spark to burn the fuel.

 

[steve murdoch]

I am not hearing anything unusual in regards to a clicking but do think there is still a slight air leak sound.
Are you using the full airbox and stock filter?

 

[Uladimir]

Thanks for all the prompt feedback!

Looking at the video again, I apologize for how crappy it is, and the noise I'm referring to is only really apparent around 0:52.

The air box is all stock along with the filter.

I was failing to idle, but this was filmed on a cold canadian night (below freezing) which is why I'm playing with the idle screw, usually it starts up fine when it's not terribly cold out.

I will have to check the tach drive that is a good suggestion, I put my actual stethoscope on it (EMT) a while ago to no avail but I will try again so I can pinpoint the source.

I have had that problem before, running on one cylinder but this is different, power is all there, just dies off at low idle.

Thanks guys!

 

[Nessism]

Wow, what a mess of a video. Can't tell jack from that other than it seems the bike may only be running on one cylinder. The noise may be the least of that bikes problems.