Carb Bowl Fuel level adjustment

[tfholly]

Hi,
I rebuilt my carbs on my '82 Gs850 and it runs badly now. I checked for vacuum leaks, etc. I adjusted the floats as per instructions. I attached a hose to the bottom of each bowl and checked the fuel level. Two carbs have a fuel level about even with screw heads. Two have a level about 1 cm higher. Would this cause bad running?

Also, when I put it together the slides weren't at equal heights. What is the proper way to put the diaphragms in? Does it make a difference as far as the slide height, or as long as they slide easily, is it OK?

It starts easily, idles pretty well, maybe a little lumpy. and revs quickly to about 1/3rd throttle at which point it loses power at higher throttle. Poor power at open throttle, but gains power when applying choke (but only at full throttle). Some popping when I coast with throttle off.

Any help would be appreciated. I have rebuilt the petcock and cleaned out the tank.
Thanks, Tom

 

[DimitriT]

How did you check the fuel level?

All the floats need to be set per the manual instructions.

The slides should all settle at the same level and should
go up and down smoothly with no hang-ups. If one of
the sliders doesn't come all the way down, remove the
slide and look for obstruction. Make sure the spring hasn't
kinked and is properly seated.

 

[bwringer]

Couple of other things:

The bike will barely run, if at all, with the airbox or airbox covers removed. It sort of sounded like you could see the carb slides while it ran, so be aware of that.

Secondly, the new needles and seats that come in most rebuild kits are garbage. There's a little spring-loaded nubbin in the middle of the needle. In many aftermarket carb kits, this spring is far too weak. When you flip the carbs over to set the float height, the float compresses the spring and it's impossible to set the correct float height.

On stock/high quality needles, the weight of the float is not enough to start to compress the spring, so you can easily set a consistent float height. This might be the source of your problem.

In addition, the jet sizes in most aftermarket kits are famously inconsistent or incorrect, and the other parts are known to be low quality and inconsistent as well. The only usable part I've found in most carb kits is the float bowl gasket, and you can buy those separately for a lot less. (at CRC2, for example: http://www.crc2onlinecatalog.com/ )

In almost every case, you're far better off keeping all the stock jets, floats, and needles, and cleaning them throughly. Get float bowl gaskets from CRC2 (or re-use the old ones), a set of o-rings from Robert Barr ( http://cycleorings.com ), and that's all you really need most of the time.

Unfortunately, I don't personally know of a consistent aftermarket source for HIGH QUALITY rebuild kits or needles (NOT Keyster/K&L). Maybe someone here can assist with that.

I know there's an outfit called Sirius in Canada that sells carb kits and a guy in New Zealand that sells needles and seats. They pop up on eBay, but I've never dealt with them personally.

 

[tholly]

Rebuild kits garbage?

Rebuild kits garbage?

I used K&L. I'm surprised the kit is that bad; how do they sell any if word gets out? The airbox and all was put back together. I noticed the slides didn't come down evenly from when it was still apart. I saw on the guide on this forum, the diaphragms have an alignment mark. I didn't pay any attention to that when assembling, either.
I'll go through them all again. Thanks for the tips. May try to put back the old jets.
Tom

 

[tholly]

Update

Update

Took the carbs apart and I found the alignment does matter on the diaphragms. The little bulge has to be lined up with the bulge on the carb body. This orients the hole in the slide a certain way. Also, I checked the needle valves and indeed the springs seem to be of varying strengths. Some of my needle valves were not closing all the way, because I bent the tab too far, trying to achieve the spec height. Anyway, since I couldn't tell from height, I just raised those a bit higher (to close sooner).
The bike runs much smoother now, even at half and full throttle, but still feels "de-tuned", with little power and noisier than usual. Applying choke makes it come to life.

I'm going to attach a tube to the screw on the bottom of the bowls again and check levels. What else can I do? Experiment with the air screws? Synchronize?
Thanks

 

[DimitriT]

Have you synch'ed the carbs?

You really should set the float heights using a depth gauge or at
least a ruler. I used a short 6" metal machine shop ruler and converted
the measurements to inches.

 

[tholly]

Float heights

Float heights

Am I right in thinking the height of the fuel in the bowl is what counts? At a certain height the valve should be closed and stop the bowl from overflowing (say if the petcock is on prime)? What is the correct fuel level? Because the springs are weak in the needle valves, the measurement of float height is just plain wrong. Should I make it so fuel shuts off at the top of the bowl? Is the most important thing that each have the same height. Or does the actual height influence the richness of the mixture?
I realize this is a lot of questions, so thanks for any input.
Tom

 

[rayserGTZ]

Float height

Float height

The usual way to check FLOAT height, is to hold the carb, not upside down, as this would compress even the stock needle springs, but gradually turn it over until the tang on the float just contacts the needle, WITHOUT compressing the spring. Then measure the height of the float bottom from the gasket face, without the gasket.
If the floats are at correct height, the fuel will be also, barring a leaky float. (Shake it next to your ear, off the carb!)
Ray.