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GS 650 Can't Accelerate

  • Thread starter Thread starter superdave
  • Start date Start date
BassCliff said:
Hi,

Maybe I'm a lazy old fuddy-duddy, but the measly few horses that you might gain aren't nearly worth the hassles and headaches of fiddling around with your carbs every other day until you, hopefully, get it dialed in properly. Don't get me wrong, there are many here who can perform this voodoo magic and get their bikes to run great. But it's just not for me. Feel free to experiment but I can almost guarantee that the outcome will not be worth the effort.

I could see attempting it on a liter bike or larger because then the "wow" factor would be greater. But on a 30 year old 650cc bike, I don't see much "wow" factor available.


Thank you for your indulgence,

BassCliff
Click to expand...

From what he describes, it is exactly what he needs - unfortunately. I rode a GS650G for 15 years, and never touched the carbs. It would pull in any gear from less than 2000 rpm to redline without a stutter or any hesitation. Throttle response was like that of a DC motor controlled by a rheostat. It had enough torque to raise the front wheel from torque alone, at 30 mph. It had throttle left at 110 - 115 mph, and didn't hesitate to accelerate at that speed. It used fuel frugally. In other words, there is a lot of performance to be wrung out of those by getting it back to 100% stock tuning.

One other thing, Superdave writes about the slides on his carbs. Stock carbs on a GS650G or GL are BS32s, and those don't have slides. Perhaps Superdave should get a stock airbox and BS32s before working on tuning.
 
themess said:
From what he describes, it is exactly what he needs - unfortunately. I rode a GS650G for 15 years, and never touched the carbs. It would pull in any gear from less than 2000 rpm to redline without a stutter or any hesitation. Throttle response was like that of a DC motor controlled by a rheostat. It had enough torque to raise the front wheel from torque alone, at 30 mph. It had throttle left at 110 - 115 mph, and didn't hesitate to accelerate at that speed. It used fuel frugally. In other words, there is a lot of performance to be wrung out of those by getting it back to 100% stock tuning.

One other thing, Superdave writes about the slides on his carbs. Stock carbs on a GS650G or GL are BS32s, and those don't have slides. Perhaps Superdave should get a stock airbox and BS32s before working on tuning.
Click to expand...

I fully admit that I am the new kid here and don't want to doubt expert advice but the carbs on my bike (and the identical parts bike) look just like the ones in the manual I bought for the bike, and nothing like the image results that came up when I googled "mikuni bs32 carbs." And the pic in the manual shows "slides" as part of the diaphragm assembly. Though maybe we are calling the same thing two different names?

Anyway, tonight I installed new boot o-rings and bolts as well as non-separated boots. (I guess the silly-cone didn't do too much before on the old ones...)

*Warning* You may think I'm crazy here... I ordered an airbox off ebay, but all day had been thinking about how you all say that part of the problem is that the airbox creates a bit of a restriction and the pods make things too lean... So I thought, "what if I create a bit of a restriction...?" So I covered each pod with a sock!

And voila! The bike is now ride-able! Of course I will install the airbox as soon as it arrives, but this totally makes me feel a bit better about ordering the aribox and the prospects of being able to really ride and enjoy the bike!

It really rode very smoothly and pulled well and seemed to have real nice acceleration. Anyway, it is much better than before.
 
Nice diagnosis, and sock-analysis.

What manual are you using that shows "slides" in the carbs? I bought my 650 new, and have the factory manual for it. Definitely B32Ses.

That being said, some people switch carbs to improve performance under some conditions. That might have been the previous owner's intention. If you can get the bike running well without finding B32Ses and replacing the present carbs, more power to you. If not, there are lots of B32Ses out there. GS850s use them, too, but I think that they have larger jets.
 
Hi,

Yes, nice work. I guess now you know that there is too much air in the system. So either bigger jets or a stock airbox should fix you up.

Here's a picture from the Carb Cleanup Series for the Mikuni BS32SS (CV) carbs:

023_Removing%20slide%20out%20top%20of%20carb.jpg



Thank you for your indulgence,

BassCliff
 
AND lets not forget that CV carbs need a bit of CONSTANT VELOCITY air to accuate the diaphrams that operate the slides..PODS that are made WITHOUT built in VELOCITY stacks dont provide the VELOCITY that is required to opertae a VELOCITY designed carb such as VELOCITY carbs..Did i mention VELOCITY enough times to make any light bulbs go off???
 
BassCliff said:
Hi,

Yes, nice work. I guess now you know that there is too much air in the system. So either bigger jets or a stock airbox should fix you up.

Here's a picture from the Carb Cleanup Series for the Mikuni BS32SS (CV) carbs:

023_Removing%20slide%20out%20top%20of%20carb.jpg



Thank you for your indulgence,

BassCliff
Click to expand...

The manual I am talking about is the Clymer manual for GS650s from 1981-1983. Mine's an '82. Not sure what year "themess" had.

But the ones in this pic also look like the ones on my bike(s) and the part labeled "slide" in the pic is the same thing in the manual. So it appears that we were indeed calling the same thing two different names.

I have a stock airbox somewhere between Ebay and here, but the fact that it rode so well last night makes me confident enough to drop the cash for new tires so I can more safely ride it longer distances.
 
In the olden days (pre-CV) the slide had no diaphram, just the slide that, well, slid, up and down to control air and fuel. The throttle cable directly controlled the slide position in the carburetor.
With the advent of CV carbs, the name stuck, even though it is now more complicated than that. A rose by any other name...
AFA keeping your current jetting, as long as you are happy with it and your plugs read OK, you should be fine. Just be aware that the addition of the socks has cut down on the amount of air entering the carbs, which means you are jetted too lean to truly take advantage of the added air you gain with pods. Which means, in a round about way, that you are giving up a few horsepower. Not a big deal IMHO, but just wanted to point that out.
 
themess said:
From what he describes, it is exactly what he needs - unfortunately. I rode a GS650G for 15 years, and never touched the carbs. It would pull in any gear from less than 2000 rpm to redline without a stutter or any hesitation. Throttle response was like that of a DC motor controlled by a rheostat. It had enough torque to raise the front wheel from torque alone, at 30 mph. It had throttle left at 110 - 115 mph, and didn't hesitate to accelerate at that speed. It used fuel frugally. In other words, there is a lot of performance to be wrung out of those by getting it back to 100% stock tuning.
Click to expand...

Yep...that sounds about right, to me. :D

I rarely ever down shift while cornering, just not needed and it is a blast to feel that much torque from such limited displacement. You expect it from the litre bikes, not from a 650 (667cc IRRC) :-k
 
koolaid_kid said:
In the olden days (pre-CV) the slide had no diaphram, just the slide that, well, slid, up and down to control air and fuel. The throttle cable directly controlled the slide position in the carburetor.
With the advent of CV carbs, the name stuck, even though it is now more complicated than that. A rose by any other name...
AFA keeping your current jetting, as long as you are happy with it and your plugs read OK, you should be fine. Just be aware that the addition of the socks has cut down on the amount of air entering the carbs, which means you are jetted too lean to truly take advantage of the added air you gain with pods. Which means, in a round about way, that you are giving up a few horsepower. Not a big deal IMHO, but just wanted to point that out.
Click to expand...

Thanks Koolaid, that seems to help clear up our miscommunication.

I know that the socks provide a little less air, but that was the point! I was trying to simulate having the factory air filter in there, as being able to ride the bike and not messing with jets is more important to me at this point than having a couple horsepower. The airbox is hopefully on the way so I hope be able to install it soon! (And have my socks back!):)
 
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