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"jumps" a bit on initial throttle, normal?

  • Thread starter Thread starter donimo
  • Start date Start date
D

donimo

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Hi all, another newb question.

When I first crack the throttle from totally closed it "jump" a bit, closest analogy I can use is an old chevy 4x4 I had with totally worn out u-joints?

Is this normal with bikes? If I am crazy consious to be super slow when cracking the throttle its ok, but its hard to do that in all situations.. The worst of it is whn I am trying to hold it just open to cruise around parking lots etc, it will dip in and out of the "jerk" zone and it is pretty rough on the neck, uh-UH-uh-UH.

if its normal then I know now, if not how does one fix this?
 
donimo said:
Hi all, another newb question.

When I first crack the throttle from totally closed it "jump" a bit, closest analogy I can use is an old chevy 4x4 I had with totally worn out u-joints?

Is this normal with bikes? If I am crazy consious to be super slow when cracking the throttle its ok, but its hard to do that in all situations.. The worst of it is whn I am trying to hold it just open to cruise around parking lots etc, it will dip in and out of the "jerk" zone and it is pretty rough on the neck, uh-UH-uh-UH.

if its normal then I know now, if not how does one fix this?
Click to expand...

First, how does it run otherwise. Second, is this your first bike I assume it is. Third, have you or the previous owner done all the maintenance recently. Fourth, your likely experiencing chain lash from slack in the chain.

You can make sure the chain is adjusted but there will always be some slack in the chain that will give you chain lash albeit less noticeable when the chain is adjusted right.

Assuming it is chain lash that your feeling, it's normal and nothing is wrong as long as the chain is adjusted.
 
I have done everything but synch the carbs and i am waitin gto double check the valves this weekend hopefully, pplus fix the exhaust holes.

It feels more throttle related, but if it IS chain lash then i guess its cool. It really feels like it goes from 0-10% throttle in one on/off, then the rest is smooth.

Bike runs as well as I can measure otherwise.

Ihave done all carb related work this site recommends.
 
I get the exact same feeling. From 0% throttle to the next bit it's quite jerky, and as you described feels like it instantly jumps to 10%. Probably just the way things are.
 
MrZig said:
I get the exact same feeling. From 0% throttle to the next bit it's quite jerky, and as you described feels like it instantly jumps to 10%. Probably just the way things are.
Click to expand...

Well it is supposed to run smoothly. my conclusion to your problem is you may have missed something while doing the carbs. My buddys 600 did/ does the same thing. I was riding it and I would give it gas and then it would kick into motion like the 10% thing your saying and he hasnt cleaned the carbs and it is super hard to start he just sprays starter fluid in the intake and it starts right up. but super hard to keep it running. so I would say carb rebuild even though I know you just did that from readin previous posts maybe you missed something?

Jake
 
There's no way in hell that it's the carbs. It's just gotta be the slack tightening up. Its just a jerky motion is all.

Carbs have been cleaned twice and rebuilt
New rear bearings
New chain & sprocket tensioned correctly.

Just the way it is. My jeep is the same.
 
Bikes with CV carbs have an inherent tendency to be rather sudden right off idle. Your best solution in slow-speed situations like parking lots is to use hold the throttle steady about 1500 rpm or so, use second gear and feather the clutch to modulate power delivery. The clutch is much smoother than the throttle.

There is also the possibility that a carb sync can help that. The purpose of the sync is to SYNChronize the throttles so they all operate at the same time. In your case, it's possible that one is not opening until the other one is open just enough to start going, then, when it opens, too, all of a sudden you have BOTH of them feeding gas, making for a jerky transition.

.
 
Steve said:
Bikes with CV carbs have an inherent tendency to be rather sudden right off idle. Your best solution in slow-speed situations like parking lots is to use hold the throttle steady about 1500 rpm or so, use second gear and feather the clutch to modulate power delivery. The clutch is much smoother than the throttle.

There is also the possibility that a carb sync can help that. The purpose of the sync is to SYNChronize the throttles so they all operate at the same time. In your case, it's possible that one is not opening until the other one is open just enough to start going, then, when it opens, too, all of a sudden you have BOTH of them feeding gas, making for a jerky transition.

.
Click to expand...

Carbs were just synced ;)

The clutch method is what I use at low speed, too. helps a lot.
 
Mine fires right up, even with no choke if it's not too cold out, doesn't even turn over, just starts. idle is a bit low (800) with no choke until it warms up. No hesitation in the powerband at any rpm or load. Carbs were soaked for a week and then blown out with carb cleaner AND compressed air. Then rebuilt with all new OEM o-rings etc.

I guess I will do the feather thing. Of course my clutch is sticky as heck right now, I ordered a new cable but no idea where it is. I should call them. Also that makes sense about the synch, never thought of it that way, its on my to do list for this weekend.

Just hard to know what is normal and what needs to be fixed with your first bike.

thanks peeps!
 
looked ok when I had the wheel off, but again I may not have a clue what to look for in a worn out cush drive...
 
it was about 6 months ago so forgive me, but I didnt have to pry it off or anything.

The most I remember is "oooh little rubber triangles, neat" I hadn't even ridden it once yet so who knows.

Ah well, I aint fixin that anytime soon, chain is in spec so I will just work around it.
 
All the shaft drive bike owners have probably forgotten but chain drives feel this way because of the slack being taken up. I'll happen every time the bike goes from decel to accel or vice-versa and the chain take up the slack.

Over time you get used to it and learn to not putt around at zero throttle.

I know you did alot of stuff but don't forget to check the chain slack, the more the slack the more violent the the jerk will feel so you don't want excess slack just enough to be in-spec. You also want to make sure your chain isn't stretched beyond it's limits or it may break on you while riding and that can be a nasty situation.
 
I checked it and it was within spec, no idea if its stretched or not though...

thanks though, puts my mind at ease!
 
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you measured chain stretch if its in spec its not stretched too much...but as stated your chain deflection(slack) and the cush drive will cause this. Next time you take the wheel of try fitting some pennies in the cush drive to take out the looseness
 
Yours starts with no choke? I need to choke mine and if I put the choke off right away it dies immedietly.
 
Try raising your idle speed to factory speed 900-1100 RPM. Id put it at about 1000RPM and call it good. Ive notice if youve got your idle speed set to low, the motor is having a tough time just keeping going, then you feed it just a touch of gas and it wants to take off like a bat out of hell... Give a shot, it may help a bit.
 
Sorry, I didnt explain that very well, my idle is set at 1100 rpm, but if I start it with no choke it idles at about 7-800rpm.

And yeah MrZig, starts right up, if anything its HARDER to start with choke, teds to stall out forst try, plus it smokes like a bajeebus...
 
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