bog down between 3k and 5k rpm

[volks28]

Continuing tuning and troubleshooting a 83 850 GS. I found many bugs like a clogged k&n air filter, a pinch in the fuel line, low voltage at the coil (temporaily fixed) cracked vaccum line at the petcock... it keeps on going...

The bike runs better now, but there is a slight bog between 3k and 5k rpm. I have good compression (130-150) golden brown/gray spark plugs ends, new spark plug caps, starts very good (less than one second! on the starter button), idles good, minimal smoke on startup when cold, good power above 5k rpm

I sprayed some carb cleaner directly on the carbs and found that the engine surged when I sprayed at one place which is directly between the carb and the engine (right at the engine head). Could this be a source of my problem?
Thanks!

[Anonymous]

There are "O-rings" that are in the carb boots that attach to the engine head. These are a source of airleaks when they get old and brittle, and are prone to failure if the boots are removed. You will need to get the Suzuki parts from www.bikebandit.com or your dealer. They are fairly cheap. They need to be the OEM part, as they are a special make to withstand the heat of the engine head. You may also want to coat them with engine grease (high temp) in order to preserve them longer.

Please see http://houseofmotorcycles.bikebandit...t_name=GS850GD

Part number 29.
They are 1.40 each...



Rob

[volks28]

Do you think it is part of the bogging down I'm having?

How difficult is it to install - scale 1-10?

There are "O-rings" that are in the carb boots that attach to the engine head. These are a source of airleaks when they get old and brittle, and are prone to failure if the boots are removed. You will need to get the Suzuki parts from www.bikebandit.com or your dealer. They are fairly cheap. They need to be the OEM part, as they are a special make to withstand the heat of the engine head. You may also want to coat them with engine grease (high temp) in order to preserve them longer.

Please see http://houseofmotorcycles.bikebandit...t_name=GS850GD

Part number 29.
They are 1.40 each...



Rob

[Anonymous]

It certainly could be..You will aslo need to check the boots themselves for cracks and tears and such. Do a search for carb removal if you do not know how to remove them. I'm not much of an expert, having no formal training. There are MANY people here that are more adept at this than I, but it is a common problem and can cause your bike to run crappy due to too much air getting sucked into a cylinder, upsetting the balance. On a scale of 1 to 10 to install, it is a 6. Not because of the rings themselves, but because you have to remove the carbs, and then take out the screws holding the spacers to the head, which in many cases on the old GS bikes, are rusted or stuck. Once you do get them out, and the new orings installed, I would replace those screws with allen heads, treated with an anti-seize. Then you need to put the carbs back on, and re-synch them if you have the tools. It may not be the root cause of your problem, but could very well be one of a few things wrong.

I have been tinkering with 2 1981 GS550T's and still have not got them running great, but am well on my waywith the help of the GSR.

Rob

[sv650]

You might also need to raise the jet needles a notch.

SV

[volks28]

Do you mean the air jet? (bottom adjustement screw?)

Thanks!

You might also need to raise the jet needles a notch.

SV

[sv650]

Nope! I meant the jet needle, as described here:

You can make your air /fuel mixture a bit richer or leaner by moving the carburetor needle
clip up or down. Move the clip down a notch to raise the needle, to richen the mixture. Move
the clip up to lower the needle, to lean out the mixture. The needle is located in the throttle
slide.

found on:

http://www.dansmc.com/carbs.htm

SV

[KEITH KRAUSE]

Rob's advice is good.
I don't know the history of the bike and what jetting adjustments may have been made, but don't start adjusting the screws, etc. If your jet needles are stock, they are not adjustable. Only Suzuki's with VM carbs or jet kits offer adjustable needles. Not your CV's.
You have found an intake leak that can definitely cause your problem. I suspect your hot idle is actually too high also. The intake leak must be fixed FIRST. You can't set the jetting mixtures with an intake leak.
The leak could be a loose clamp if your lucky, tighten that first and test.
If not, then the o-ring or the manifold itself is leaking. Try tightening the manifold screws first, they could be loose? If not, then it's the manifold or o-ring. The o-ring is more likely the problem but if the manifold has cracks in it then it's possibly leaking too.