Clutch adjustment = Poor engine braking.

[bombshelter13]

I adjusted my clutch the other day because I suspected it was sticking slightly. My initial adjustment was off slightly: after a quick ride around the neighborhood, I noticed it seemed to be slipping slightly when accelerating past 30 MPH... so, I pulled over, pulled out my tools, and did a second adjustment - loosening it a bit at the release mechanism, so that the clutch was more engaged in it's resting position.

After the second adjustment, everything seemed pretty good, most of the bike's behavior seems correct, except one thing: If I chop the throttle slightly in an attempt to cause engine braking, the rev's drop a lot slower than they did before the adjustment - instead of getting immediate engine braking, the rev's seem to slowly fall back downwards, slowing down the bike's forward motion very gradually instead of getting good engine braking.

Now, it's possible that these might not actually be related and might have just coincidentally happened at about the same time, but I'm wondering if maybe I need to do a third adjustment. Thing is, I'm not really sure whether this behavior would be caused by the clutch being too tight or too loose.

So... if this slow rev dropping is related to my clutch adjustment, it too loose or too tight?

NOTE: When I talk about loose and tight, I'm not referring to the lever end, I'm referring to the release mechanism - i.e., when I say tighter, I mean the release mechanism is applying more pressure to the clutch pushrod when the cable's in it's resting state (clutch more disengaged by default). When I say looser, I mean the release mechanism is applying less pressure to the clutch pushrod with the cable in it's resting state (clutch more engaged by default, less maximum disengagement when lever is pulled)

 

[invictus43]

There should be no pressure on the pushrod whatsoever when the clutch is released. You should have freeplay in the cable and that should also extend to the pushrod. You should not be applying release pressure whatsoever to the pushrod when the lever is released.

 

[bombshelter13]

invictus43, I was told to turn the release adjustment screw in just until resistance is felt, so that's the level of pressure I'm talking about, it's certainly not a great deal.

 

[invictus43]

The screw you're turning in should not engage the clutch whatsoever. You can turn it in until you feel it just contacts the pushrod, but no more than that. Otherwise your clutch is beginning to disengage and you'll have some level of slippage, even a little. This is bad. Better to err on the side of less contact than more. And make sure you have freeplay in the cable at the lever when you're done.

 

[bombshelter13]

Alright, I'll try backing it off another fraction of a turn and see whether it changes anything.

Still interested in hearing additional or alternate explanations since I'm sure there's more than one way this slow RPM drop/poor engine braking I'm noticing could happen.

 

[invictus43]

I think it's just coincidence. You're probably thinking too much about it..seriously. A clutch should have no release pressure when the lever is out. The adjustment screw you're playing with is just a way to take out the slack in the lever mechanism so you don't have any play. It's not intended to put any pressure on the pushrod when the lever is released.

 

[bombshelter13]

If it's not clutch related, any ideas what could be causing the slow RPM drop when the gas is released?

Engine braking ability is almost gone, and if I close the throttle while going downhill without pulling in the clutch, instead of slowing quickly as you'd expect, the RPMs drop very slowly as if the wheel was pulling the engine back up to speed. If I pull in the clutch, RPMs drop immediately as one would expect, but releasing it again seems to cause the engine speed to get 'pulled' back up to the previous speed.

So... I'm going downhill in second, about 5K RPM at 50 KM/H... close the gas, the bike will slowly coast down to about 20 KM/H over about 50 meters or so.

If I do the same thing, but pull the clutch in before closing the gas, RPM's drop immediately, but when I let the clutch back out they'll be pulled back up to 5K or so and then slowly coast downwards as described.

 

[djltoronto]

If I chop the throttle slightly in an attempt to cause engine braking

Don't chop it slightly, chop it fully.

There should be no pressure on the pushrod whatsoever when the clutch is released. You should have freeplay in the cable and that should also extend to the pushrod. You should not be applying release pressure whatsoever to the pushrod when the lever is released.

Correct

invictus43, I was told to turn the release adjustment screw in just until resistance is felt, so that's the level of pressure I'm talking about, it's certainly not a great deal.

You were told by who?

Pretty sure the service manual will read " turn the adjustment screw until resistance is felt - then back it off 1/2 turn (or a 1/4 turn) or some amount of turns. There should certainly never be any pressure there when the clutch lever is at rest "disengaged"

The screw you're turning in should not engage the clutch whatsoever. You can turn it in until you feel it just contacts the pushrod, but no more than that. Otherwise your clutch is beginning to disengage and you'll have some level of slippage, even a little. This is bad. Better to err on the side of less contact than more. And make sure you have freeplay in the cable at the lever when you're done.

Yup

So... I'm going downhill in second, about 5K RPM at 50 KM/H... close the gas, the bike will slowly coast down to about 20 KM/H over about 50 meters or so.

If I do the same thing, but pull the clutch in before closing the gas, RPM's drop immediately, but when I let the clutch back out they'll be pulled back up to 5K or so and then slowly coast downwards as described.

This sounds exactly normal. My GF rides a GS500f and your description is exactly what I would call normal.

 

[djltoronto]

From the Haynes Manual -


http://www.mediafire.com/?w1zpcss0nde8scb

 

[bombshelter13]

Don't chop it slightly, chop it fully.

Tried this while experimenting further, and the results were about the same.

You were told by who?

Haynes service manual provided a basic description and I looked up further elaboration on the gstwins forum. Just in case this was the issue I backed it off another 1/3 of a turn or so an hour ago, but it hasn't made much difference.

This sounds exactly normal. My GF rides a GS500f and your description is exactly what I would call normal.

Strange, mine didn't behave that way until about 100 km ago. Wonder what could have changed and how I can change it back, as I much preferred the way it was for the previous 4000km, with much better engine braking performance. Before, chopping the throttle would cause an immediate and significant speed reduction, now it barely engine brakes at all. If that's normal and my previous situation was abnormal, I think I preferred abnormal by far.

 

[djltoronto]

Strange, mine didn't behave that way until about 100 km ago. Wonder what could have changed and how I can change it back, as I much preferred the way it was for the previous 4000km, with much better engine braking performance. Before, chopping the throttle would cause an immediate and significant speed reduction, now it barely engine brakes at all. If that's normal and my previous situation was abnormal, I think I preferred abnormal by far.

MY GF's GS500f is very smooth to ride - chopping the throttle closed from mid RPM's in second gear results in a gentle / casual deceleration. it's very very un-dramatic.



Another thing, if your GS500 clutch is not slipping during acceleration, it's certainly not slipping during deceleration. Your deceleration issues are not related to clutch slip. Did you recently make any other changes? Did you change the idle speed at all?

 

[bombshelter13]

Another thing, if your GS500 clutch is not slipping during acceleration, it's certainly not slipping during deceleration.

Good to know, it doesn't appear to be slipping (as far as I can tell) during acceleration currently.

Your deceleration issues are not related to clutch slip. Did you recently make any other changes? Did you change the idle speed at all?

I've found my bike to be pretty sensitive to temperature, and find I have to adjust the idle screw whenever the temperature's changed significantly since the previous day - there doesn't seem to be a screw position that's within the specified idle speed on both cold days and hot ones. My main reasons for believing the problem to be related to clutch adjustment are timing (it occurred almost immediately after doing my first full three-point adjustment of the clutch cable) and the fact that RPMs seem to drop normally if the clutch is pulled in, the sticking only seems to occur if the clutch is still engaged. If it's carb related then there's clearly something I'm missing as far as how carbs work (which is entirely possible, I really don't know a great deal about carbs), as my understanding was that carb related RPM hanging would probably also happen with the clutch pulled in.

Thinking of trying to do a carb cleaning soon in the hopes that this might help with the idle, which would be a learning experience since I've never done one before. kinda wish I had someone who'd done it before who could guide me through it, would probably be willing to pay a few bucks for the assistance if you have done it before.

 

[djltoronto]

Good to know, it doesn't appear to be slipping (as far as I can tell) during acceleration currently.



I've found my bike to be pretty sensitive to temperature, and find I have to adjust the idle screw whenever the temperature's changed significantly since the previous day - there doesn't seem to be a screw position that's within the specified idle speed on both cold days and hot ones. My main reasons for believing the problem to be related to clutch adjustment are timing (it occurred almost immediately after doing my first full three-point adjustment of the clutch cable) and the fact that RPMs seem to drop normally if the clutch is pulled in, the sticking only seems to occur if the clutch is still engaged. If it's carb related then there's clearly something I'm missing as far as how carbs work (which is entirely possible, I really don't know a great deal about carbs), as my understanding was that carb related RPM hanging would probably also happen with the clutch pulled in.

Thinking of trying to do a carb cleaning soon in the hopes that this might help with the idle, which would be a learning experience since I've never done one before. kinda wish I had someone who'd done it before who could guide me through it, would probably be willing to pay a few bucks for the assistance if you have done it before.

If you have any friends with a GS500 - swap bikes for a short ride and compare results.

 

[bombshelter13]

If you have any friends with a GS500 - swap bikes for a short ride and compare results.

Sadly I don't. :/

 

[skapan]

Did you do anything else while you were adjusting the clutch? Like maybe moved the cables around and got the throttle cable in a new position that stops it from closing as it did before? Sounds like something was moved/changed that has resulted in the performance difference. And you shouldn't need to mess with the carb every time the temperature changes. Idle is set with the throttle stop screw, not with the air screw, so something is going on there. Just trying to help.

 

[bombshelter13]

Did you do anything else while you were adjusting the clutch?

I didn't do anything else intentionally, so if I managed to achieve anything else it was accidental...

Like maybe moved the cables around and got the throttle cable in a new position that stops it from closing as it did before?

I didn't intentionally make any adjust to them, and didn't have to, for instance, move them out of the way to do any of my clutch adjustment - the stock routing is such that those sets of cables don't really interfere with each other... so the amount of movement they should have experienced is the amount one would expect from having the bike on it's center stand and turning the bars back and forth a few times. Nothing unusual.

But just in case something throttle cable related was the issue, yesterday I pulled out my Haynes manual and re-adjusted the throttle cables - which, basically resulted in me concluding that they were probably adjusted correctly before I started, as following the instructions in the manual basically resulted in me putting them back where they were before I started the re-adjustment.

Sounds like something was moved/changed that has resulted in the performance difference. And you shouldn't need to mess with the carb every time the temperature changes. Idle is set with the throttle stop screw, not with the air screw, so something is going on there.

Okay, the terminology here's throwing me off... you make mention of the 'throttle stop screw', and the 'air screw'. It's not clear to me which you mean when you say 'throttle stop screw'. There's a little white screw coming off the bottom of the carb that my service manual describes as being for adjusting the idle speed... that's the one I'm adjusting. There's a seperate 'air mixture screw' - I don't know if that's the same as what you call the 'air screw', but I didn't adjust that one.

As I think I mentioned, I've suspected for a while that there me be some bit of gunk in the carbs... could a piece of gunk coming un-clogged from one spot in the carbs only to get sucked into (and re-clog) another cause this? Maybe something moved from gunking up a jet to gunking up a float, or a float that was sticking closed is now sticking open? Would any of these have this sort of symptom (bad engine braking, but normal RPM drop with clutch in)?

Just trying to help.

Totally appreciate it, the more ideas I can get the better!

 

[RC-31]

Okay, the terminology here's throwing me off... you make mention of the 'throttle stop screw', and the 'air screw'. It's not clear to me which you mean when you say 'throttle stop screw'. There's a little white screw coming off the bottom of the carb that my service manual describes as being for adjusting the idle speed... that's the one I'm adjusting. There's a seperate 'air mixture screw' - I don't know if that's the same as what you call the 'air screw', but I didn't adjust that one.

As I think I mentioned, I've suspected for a while that there me be some bit of gunk in the carbs... could a piece of gunk coming un-clogged from one spot in the carbs only to get sucked into (and re-clog) another cause this? Maybe something moved from gunking up a jet to gunking up a float, or a float that was sticking closed is now sticking open? Would any of these have this sort of symptom (bad engine braking, but normal RPM drop with clutch in)?

The throttle stop screw is the one that you want to be adjusting for idle -- and yes, it is common to have to adjust this a lot. It is the screw that is located with the throttle cables @ the carb. It literally keeps the throttle plate open a (however much you set it) bit when you let go of the gas. The problem sounds like the idle is too high, ie the throttle stop screw is extended too far.

When your bike is warm, back off this screw until the bike barely idles. Take it for a spin and see if the engine braking has improved.

Don't touch the other screw. That is a different adjustment. It's an air/fuel mixture screw: Don't bother with it.

It doesn't sound like you have mystery debris in your carb. If you did, you would have almost certainly notices choppy power delivery and off-idle stumbling; not just a problem with over-run.

 

[djltoronto]

The throttle stop screw is the one that you want to be adjusting for idle -- and yes, it is common to have to adjust this a lot. It is the screw that is located with the throttle cables @ the carb. It literally keeps the throttle plate open a (however much you set it) bit when you let go of the gas. The problem sounds like the idle is too high, ie the throttle stop screw is extended too far.

When your bike is warm, back off this screw until the bike barely idles. Take it for a spin and see if the engine braking has improved.

Don't touch the other screw. That is a different adjustment. It's an air/fuel mixture screw: Don't bother with it.

It doesn't sound like you have mystery debris in your carb. If you did, you would have almost certainly notices choppy power delivery and off-idle stumbling; not just a problem with over-run.

On his bike the throttle stop screw/idle adjustment screw is the one he's been adjusting.

This is correct.

There's a little white screw coming off the bottom of the carb that my service manual describes as being for adjusting the idle speed... that's the one I'm adjusting.