Bad Vibrations

[gssuzukixxx]

My '79 GS850 had rattle/vibration until I discovered one of the horns under the tank was slightly touching the tank. When I moved the horn away from the tank the rattling stopped.

Brian

[raistian77]

What did you use to sync the carbs ? I did a mechanical sync on my 850, always ran good. Did a sync with motion pro set up. Made the engine noticeably smother..

same tool, Steve double checked with merc sticks

[bwringer]

Hmm... this is definitely odd. This should be one of the smoother 4-cylinder engines.

Have you hooked up a timing light to verify that 1/4 and 2/3 are firing at the correct times?

If you have, for example, 1/4 timed right but 2/3 is off, you can get some strange vibrations. I'd also hook up the timing light's pickup to each plug wire and verify that it's firing as expected and the wires are hooked up correctly.

[tkent02]

What I did is remove 1 and 4 plugs bring 1 to TDC measure with depth micometer then compare to 4. diffrence is almost nill.

Measure with the pistons half way down, a few degrees of twist will give a measurable difference in piston height then. When they are all the way up, even a large twist won't displace the pistons much. The difference should be absolutely zero.

[BadBillyB]

Yeah, I was thinking the same thing. The piston dwells at TDC for a couple degrees. Does, I hate to say, sound like a twisted crank. If you knew someone with a really nice degree wheel and a piston stop, you might see it on the degree wheel...Comparing cylinder 1 to cylinder 4...absolute TDC...Short of that, the method used by crank builders is to run a precision rod through all four connecting rods at the same time....Billy

[raistian77]

Ok, checked piston travel is equall in 1 and 4. Ran a compression check, hot.
1-135
2-130
3-130
4-100

Seems I am loosing some compression through the head. Did a valve clearance check again and found the clearance barley acceptable. When I first got the bike the clearances were way to tight. Wondering if the PO ran the bike without adjusting the valves for to long. Gonna need to pull the head and grind the valves.

Installed the Dyna-S today, like the stability of the timing better.

[tkent02]

Gonna need to pull the head and grind the valves.

NO, you don't. Run it a while with the valves adjusted correctly, go 1,000 miles or so. Check that cylinder's valve clearances again after 100 or so. The compression will come up. The compression is not the reason for the vibration anyway, some engines with terrible compression run very smoothly at cruising RPM. There is another problem.

But if you like pulling heads and spending money, go for it, just don't be surprised afterward when it still vibrates.

[bwringer]

Let's back up a bit -- exactly how bad is this vibration, and how does it compare to similar 4-cylinder bikes you've ridden?

It's an inline-four -- it's gonna buzz.

For example, my bike is wearing Manic Salamander bar-end weights, the bars are filled with lead shot, and it's probably one of the smoothest GS850s on the planet. But I still have to be careful to change hand position often so I don't go numb.

So are we talking a somewhat normal amount of vibration, or are we talking "load of cement in the washer"? What are you comparing it to?

[raistian77]

NO, you don't. Run it a while with the valves adjusted correctly, go 1,000 miles or so. Check that cylinder's valve clearances again after 100 or so. The compression will come up. The compression is not the reason for the vibration anyway, some engines with terrible compression run very smoothly at cruising RPM. There is another problem.

But if you like pulling heads and spending money, go for it, just don't be surprised afterward when it still vibrates.

Before I started it for the first time I checked valves (way to tight)
made the adjustment
checked again 2,000 miles later, to tight again so I reajusted again
now its 2,000 miles later and the valves are back to being on the borderline of being to tight, a .0015 shim will barely slide.

Is it possible the valves are reseating after being way out?

[raistian77]

Let's back up a bit -- exactly how bad is this vibration, and how does it compare to similar 4-cylinder bikes you've ridden?

It's an inline-four -- it's gonna buzz.

For example, my bike is wearing Manic Salamander bar-end weights, the bars are filled with lead shot, and it's probably one of the smoothest GS850s on the planet. But I still have to be careful to change hand position often so I don't go numb.

So are we talking a somewhat normal amount of vibration, or are we talking "load of cement in the washer"? What are you comparing it to?

This is the first bike I have been on since 1996.
Never been on a 4 cylinder bike before this one.

at 4,000 rpm the handlebars and highway pegs buzz and tend to put hands and feet to sleep.

at 5,500 rpm the whole bike begins to buzz kinda hard.

guess I need to look into bar end weights.

[tkent02]

That sounds like way too much vibration. Try this, let someone with GS experience ride it, or ride someone else's GS to compare. It may be something obvious to a GS nut.
My GSes of all sizes are all just about smooth as glass when they are working right. No bar end weights, no fancy grips, no nothing. 850s usually are the smoothest of the bunch. You can maybe feel a little buzz at high RPM if you are looking for it, but it's not really noticeable. If I ride it all day my ass hurts, but not the hands.

Yes it is possible and it is likely the valves will need a few adjustments after being too tight like that. That's how the compression improves with a few miles.

[JEEPRUSTY]

This is the first bike I have been on since 1996.
Never been on a 4 cylinder bike before this one.

at 4,000 rpm the handlebars and highway pegs buzz and tend to put hands and feet to sleep.

at 5,500 rpm the whole bike begins to buzz kinda hard.

guess I need to look into bar end weights.

you dont have bar end weights?
I thought all bikes had em stock.

[raistian77]

Dang, I should have asked Steve to test run it when he was here

[JEEPRUSTY]

Before I started it for the first time I checked valves (way to tight)
made the adjustment
checked again 2,000 miles later, to tight again so I reajusted again
now its 2,000 miles later and the valves are back to being on the borderline of being to tight, a .0015 shim will barely slide.

Is it possible the valves are reseating after being way out?

Shim and bucket gurus isnt that an extreme amount of clearance loss in 2000 miles?

Is it possible that your timing chain jupmed not sure if this is possible without breaking the engine.

Also maybe you are not checking your clearance properly.
There is a video of a gs 500 being done on youtube but I dont know if the process is the same.

[tkent02]

you dont have bar end weights?
I thought all bikes had em stock.

Just thumpers, V twins and other designs with poor primary and secondary balance. Some of them even have balance shafts and still need bar end weights. Inline fours generally don't need them. Should be about as smooth as a car engine.