TOPIC:

What kind of performance does this diaphragm introduce to my bike? What good is it? What does it really do? I turn the throttle but the rod to it doesnt even look like its moving. My Clymer manual says something about it but it doesnt answer my question.

The diaphragm is a way to ensure the engine does not see more fuel then it has the volumetric efficiency to consume. There is no mechanical connection in between the carb slides and the throttle grip. Instead there is a butterfly in each carb connected to your throttle grip, but again no mechanical connection between the butterfly and the slide.

When you open the throttle the butterfly's in the carbs open allowing more air into the engine the airflow is measured by a sensing port in each carb that is ported to the diaphragm chamber. As the airflow through the carbs increases its signial to the diaphragm increases as well, causing the slide to lift and raise the needle up out of the main jet but only as much as the engine demands(if tuned properly).

Peace&Love, Darren

Ok, That sorta made sense. Ill just have to read it repeatedly, but I do get what you are saying

What diaphragm are you talking about?

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Post edited by: wiredgeorge, at: 2006/12/06 08:40

lower rev range smoothness is what the vacuum diaphram slider is designed for.

it is a next generation upgrade from the mechanical slide carbs of yesterday.

the intake air velocity is increased to insure more complete fuel atomization at all rev ranges.

the slide is not controled by the throttle twist grip, it is controled by the pressure differences inside and outside the carb while the engine is running.

Post edited by: trippivot, at: 2006/12/06 09:24

I am talking abotu the accelerator pump diaphragm George!

hhmmm..Wondering about this too..
Waiting with baited breath for a reply...

I was wondering the same thing, I could explain accelerator pump operation but WG could do a better job. I'm not real good wit wurds

The accelerator pump diaphram acts as a pump to squirt fuel down the throats of the carbs into the cylinders. This will help with throttle response when the throttle is opened rapidly.

The fuel goes through those four tubes under the carb bowls to the port on each carb that the gas squirts out.

Simple!

FMBA explained it well but I will also try and explain this. If you take your carbs off without draining them, open the throttle bellcrank quickly. It is attached to the rod that actuates the arm on your accelerator pump. When the arm move up, the diaphragm(s) suck gas through the #2 carb's pump mechanism. The gas goes up through the hole in the edge of the #2 carb directly and is forced across the joining gas line in the other bowls through holes in the edge of each of these bowls. The bowl mates up with a nozzle in the throat of each carb. In effect, when you open the throttle, ONE squirt of atomized gas goes into the combustion chamber on each cylinder if the whole mess works as it should. The reason is that the carbs the pumps were installed on were pretty lean in the idle circuit (small pilot jet) and lean jet needle/needle jet combo and the extra gas is required for "throttle response". If you open the throttle slowly, no squirt. I am guessing here but I assume this was a way around EPA testing issues... At idle, the little pilot jets would do their job being lean and then at some higher rpm, if you rolled the throttle on slowly, still that same leanness so loved by the EPA testers... I am also guessing but LEAN means burning hotter which burns up more "stuff" rather than a richer burn which allows more nasty hydrocarbons to make it to the atmosphere. I remember going out on the golf course in the early 70s and not being able to follow the ball through the yellow sky... the smog stuff did help. I doubt the WAY Kaw chose to make their vehicles environmentally friendly at first was the best way but when they changed to the reed valve reburn system in 1979, they are still doing about the same thing today.

I have to agree with trip's comments; the constant velocity carbs are smoother across the range of operation and likely are capable of flowing more air and fuel as well. Another thing that smoothed out the ol' Kaws is that heavy crankshaft they stuck in the KZ1000 engines (like the MK II engine in my shafty). It feels almost like an electric motor compared to the lighter and quicker spinning crank in the Z1 engine in one of my carb test bikes. I am currently using VM26s in my personal ride (the KZ1000E1 ST) because I am using a Z1 airbox... the OEM airbox that came with the bike is lacking the rubber manifolds. When I get some ambition, I will mod the stock airbox to take bigger runners using PVC or something from Home Depot and stick some BS34s or CV34s on the bike. I suspect you might just get a tad better fuel economy as well but this is a seat of the pants comment as I haven't really done a back to back fuel economy test using CV/BS vs VM carbs. Gas is atomized a lot more effectively in CV carbs towards the lower rpm range.


trippivot wrote:

lower rev range smoothness is what the vacuum diaphram slider is designed for.

it is a next generation upgrade from the mechanical slide carbs of yesterday.

the intake air velocity is increased to insure more complete fuel atomization at all rev ranges.

the slide is not controled by the throttle twist grip, it is controled by the pressure differences inside and outside the carb while the engine is running.<br><br>Post edited by: trippivot, at: 2006/12/06 09:24