Tick Rattle and Roll, what sound is this? 850G

[Redman]

My 80 850G makes a fast ticking engine noise, almost a rattle, noticable when accelarating thru 2 - 3krpm in lower gears (probably just cant hear it at higher speeds). Doesnt do it at idle. More of a 'ticking' or faint 'clicking' kind of a sound because it is rather regular repeating tic-tic-tic-tic-tic, but not exactly a uniform ticking but yet a ticking, as opposed to a random rattle. Doesnt seem to run any different when it is doing this. It is directly proportional to engine rpm. Sounds like from top or from cyclinder area, more than from lower part of engine. Doesnt always happen and is sometimes less or sometimes more, but not real loud, but maybe I should be more concerned about it than I am. I dont expect to be getting an other bike in years.

I have seen discussions about piston slap, ignition knock, and cam chain rattle, and cam lobes slapping cuz they are too loose (need adjusting/shimmed) sounds. The description of these sounds all seem about the same to me.

I had head off (to replace head gasket) 2 years ago, and had valves lapping 'touched-up' and valve shims set at that time, about 3-4 thousand miles ago, so I dont really suspect a valve shim problem. Was making this sound a little bit last season and now a bit more this season.

I have had cam chain rattle-knock (that was scarry) a few years ago and had shop reset tensioner (after I tried). So I kinda know what thats like, so I say its not a cam chain rattle, but more of a tick-tick-tick-tick.

Oil change did quited it down a little bit, for a little while.

Any suggestion from any of you Cick and Clack GSBrothers on how to distinguish between these variuos other potential causes of this noise? Or any other factors to look for that have influence on this happening? Thanks guys.

[daveo]

'Tic-tics' are usually a loose valve, better loose than tight though, you may want to check them if it's bothersome to you

[focus frenzy]

if the noise happens with the engine warm but not when cold, I would suspect it is ignition knock, you will get ignition knock primarily below 3K rpm's and it is mostly during warmer (hot) weather when it shows up.
ignition knock, or detonation as it is more commonly know, is very bad, it is the fuel air mixture igniting prematurely and the flame front collides with the cylinder walls and the flame front from the spark plug, it is violent and hammers at the pistons and the cylinder and head, it can eventually cause severe damage to the pistons. ( broke skirt, cracked piston) what grade of gas are you running? if you are running regular unlead try super to see if it has any effect.
also does the noise get worse then lessen as you open up the throttle at that RPM range?
does the noise stop if you back off the throttle?

it can be hard to tell what a noise is without hearing it, but from your description it sounds like detonation.
If you bike has a fare amount of miles on it, you may have carbon build up in the combustion chambers, there are a few premium gas additive cleaners that can help clean it out.
the old time water trick works very well for cleaning out carbon build up.

[Redman]

Thanks guys.
Yah, Is hard to describe. Maybe as 'tic' is not best description.
I quess I described it as a 'tic-tic-tic' becuse I've heard what I thought was ignition knock detonation in car-truck and it was a more random 'tic-tink-kink-clink-kackle-knackle-kich-knackle'. But what is happeing on my bike is more of a regular repaeated 'tic-tic-tickle'.
OKAY, you can all laugh at me like I do when listning to Car-Talk.

After some further observation, yep, does happen more when warm/hot (over 85 is hot here in Michigan), and does stop if I let off even slightly, and returns if I get back on it (less than 4krpm). And does it a whole lot less after filling up on mid-grade (too cheap to try premiumn, west michigan, dutch, you know). SHould look to see what manaul recomends for gas.

Thanks for description of how/why detonation is bad, didnt fully understand that before.

Also I take all this as an indication that I should be downshifting if I'm trying to accelarate at that low of RPM if its hot outside and I'm too cheap to buy mid-grade gas. Or is there something else I should be concerned about?