Knock and drop in revs!?

[billsy]

Hi guys....done a search but just wondered if anyone recently has heard of a prob with a gs500 producing a knock sound along with a drop in revs intermittently....this only happens when the bike is cold   any thoughts??

[ohgood]

Hi guys....done a search but just wondered if anyone recently has heard of a prob with a gs500 producing a knock sound along with a drop in revs intermittently....this only happens when the bike is cold   any thoughts??

time for new plugs ? have you checked them for color ?

by knock, are you certain it's not just the camshaft end play we all get to listen to ?

does it do it at idle ?
at WOT ?
at partial ?

could be allot of things, I'd start with the easy stuff like carb synchronization myself. outta sync usually sounds like a 'tick' and not a knock.

[Rema1000]

When my GS is very cold, and I start it up, sometimes it will go "chug chug chug chug WHACK chugga chugga chugga", where the WHACK sound is a bit like someone rapped a hammer against a table vise.  There seems to be a tiny hiccup when the knock happens.  Sometimes the engine dies altogether right when it makes the knock sound.  Other times it keeps running.  If the engine keeps running past the knock, then it never knocks a second time.  This usually only happens when starting in winter (e.g. 40 degrees out), pretty much never in summer.

Does that sound same or different to your knock?

[scottpA_GS]

When I saw the title I thought it was a play on a rap song...


Knock Knock and Drop it 

OK.... Sorry.

[coll0412]

Sounds like the starter clutch is stuck or something. People typically complain that when they start the bike and its really cold(~40°F) that it will turn over a few times and then make a sudden loud noise(like a hammer hitting something) on the left side of the bike. The only thing is that this may also destroy the magnet on the rotor over time. My bike used to do this but I don't ride when it is so cold anymore it has stopped.

[billsy]

Yep...checked plugs...nice and powdery grey...gap was pretty wide so adjusted and seems to be ok now....might get the electrics checked out...dunno where it`s been before it got to me   ...thanks guys   

[TheTazZ]

Just to check - adjusting/new plugs will fix this?
I have the same issue but havent found the time to do something about it yet...

[Rema1000]

Sounds like the starter clutch is stuck or something.

Thanks for the heads-up, that doesn't sound good!  Where did they do their quality testing?  Japan?! (j/k)

[larryrt]

I just bought a gs500f (08) a month ago. Only 50 miles so far! Same thing is happening.
After starting I gradually increase the throttle between 1500 and 2000 rpm and it knock and the rpm sharply falls back. I can have the bike completely warm and it will do the same thing. In neutral. There is a lot of knocking .....

[ohgood]

I just bought a gs500f (08) a month ago. Only 50 miles so far! Same thing is happening.
After starting I gradually increase the throttle between 1500 and 2000 rpm and it knock and the rpm sharply falls back. I can have the bike completely warm and it will do the same thing. In neutral. There is a lot of knocking .....

that's too bad, and it's warrantee time for you.

[gsJack]

I've occasionally had that same knock and rev drop at idle just after starting when it's cold outside since the first winter I had my 02 GS500.  Bought it in Sept 03 with about 4k miles on it.  It concerned me a bit at first but I've mostly just forgotten about it since and it's still running like new 5 years and 60k more miles later.  I think it will be OK if I don't worry about it, not serious enough to stop riding year round.   

My 97 GS that I bought new and put 80k miles on never did that with the same kind of year round usage.

[The Buddha]

Knock and drop idle if it does that with a fair bit of regularity = lean misfire.
When cold - under 5 seconds of starting its definetly lean misfire. Maybe check if your choke is working else some thing else is clogged/jetted lean.
When its warming up if it does it, it can be a valve just about to go tight ... it will get worse pretty rapidly and it will start to stall.
If it does it when hot and not any other time, its definetly a lean misfire. This you have to clean the carbs, and if they are clean, you have to rejet.

Starter clutch will clunk only when you press the start button.
If it happens as you're revving up, there is some bad setup, like 1 float is too low or somehting ...
New plugs sometimes make it worse ... a clean used plug is your best bet for diagnosing your way out of a problem. Swapping plugs is right only as a routine thing, not as a trouble shooting guide.
Cool.
Buddha.