Engine rattle

[Guest]

Hi all,my gs850 had a horrible engine rattle so went to check/adjust the shims however they seemed fine, if anything quite tight. However decided to check the cam chain at the same time and noticed that the gap on the top of the chain from timing mark 2 to timing mark 3 was 19 rivets and manual said it should be 20. Could this have been causing the engine rattle? Cheers Wayne

[Dogma]

Incorrect cam timing like that (just one tooth) will cause you to have very low power. Did you count the link at each end? I can vouch for the fact that it's easy to mis-count these, especially on the 850 with that little idler pulley. This will not cause a horrible rattle, unless the timing is off far enough for valves and pistons to collide.

When properly adjusted, the valves should sound like a sewing machine. Not all that loud, but a steady tapping sound.

Sometimes cam chain tensioners get sticky and allow the chain to slap around.

Can you describe the noise or post a recording?

[wdavie]

I'm goin to put the engine back in the bike hopefully monday and try running it again, if noise still there Ill try to video it on my phone and post it.

[850 Combat]

When the carbs are not synchronized, you can get a pretty amazing rattle out of the clutch and primary gears. Kind of a loud chatter on mine.

[chef1366]

Clutch rattle?

[Swarley]

Low idle rattle

I have a 79 1000, and if it's adjusted to idle under 1100 rpm it rattles really bad. I saw someone mention if the carbs aren't synchronized it can rattle, could this be the case, and what idle should it be set at? Thanks!

[cowboyup3371]

Look at the service manual for your bike (found on Basscliff's site) but I've been told that 1100 - 1200 is about right for most of these things.

[Steve]

Look at the service manual for your bike (found on Basscliff's site) but I've been told that 1100 - 1200 is about right for most of these things.

Actually, the smaller ones (like your 550) will have slightly higher idle speeds.

I think the twins idle around 12-1300, but the larger bikes call for 1050 +/-50, according to the manual.

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[Swarley]

Thanks, I didn't know where to look up the manual, as I don't have one. I'm used to cars where 1000+ is hi. Always love learning something new!

[Steve]

Thanks, I didn't know where to look up the manual, as I don't have one. I'm used to cars where 1000+ is hi. Always love learning something new!

Cars have a much larger rotating mass and flywheel effect that keeps them running smoother at lower idle speeds.

The number of cylinders can affect idle speed. You need higher speeds to have enough momentum to get the crank from one firing pulse to the next.
More cylinders means the firing pulses are closer together. Idle speed on my Wing is 650.

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