TOPIC:

dutchz wrote:

This is what it looks like straight down the throat... You can clearly see my carbs have been modified from stock by removing all the blind ports and blending the edges.

Sander,

Filter / Stack setup looks fantastic!

I don't like what looks like a sharp edge in the carb bore where the bell has been blended though.


Looks like the body was ground so much the edge of the jet block protrudes now. I downloaded the photo and blew it up for a good look.....that's sure what it looks like

Sure seems to me like a turbulence generator right in a spot where you want laminar flow to create low pressure across the needle jet discharge nozzle... Maybe nothing...maybe a source of the jetting issues you've run into.

Here's a larger crop. It's not a sharp edge as I recall it, I thought it was soft - just like it is on the left between the ports. As far as I can see they've knocked out the blind ports that were on the right and blended the throats out towards the edges but I don't think the removed any material towards the slides.

I found some older pictures with different light, maybe that helps.

One more

Going by the last pic......looks OK

Going by the one before that....looks like a depression.

You know what to look for bud.... and if you want that whole setup tested, the offer is there for you anytime

29 smoothies....about 83CFM tested bare. Same as a street cut port job. That's why I decided on that level of flow for that stage of porting

Aah OK I think I see what you were looking at now, were you concerned with the area closer to the slide? Almost level with the square recess around the needle jet discharge nozzle? I don't think there is a sharp ridge there, but I'll have another look over the weekend. Far as I remember that's smooth all the way into the bore.

I know the offer is there Larry, thanks again. I'll probably go through the motor some time this winter and have some down time, that would be a good time to send you my carbs and the stack/filters so you can flow them. That will be VERY interesting!

super cool

dutchz wrote:

I found some older pictures with different light, maybe that helps.

Sander,

It this photo, looking at what appears to be a ground in recess on the right running from the main a/c jet boss to the enrichener air circuit boss on the right.

In other pics that recess looks like it forms a sharp ridge at the bottom right section of the carb bore.

All I'm saying is if there is a sharp ridge there, it could cause turbulent flow along the floor of the carb bore. That, IMO would not be desirable.

Turbulence in the needle jet area would disrupt the pressure differential that causes the fuel to rise in the needle jet.

If the pressure differential fluctuated, then fuel flow would fluctuate as well.

Is that happening? I don't know...just appears to be possible from my experience flow testing

kawsakiman wrote:

so when are you making me a set?

I spoke to Wompy, shoot him a PM if you want a set, his handle is wompy5000

larrycavan wrote:

It this photo, looking at what appears to be a ground in recess on the right running from the main a/c jet boss to the enrichener air circuit boss on the right.

In other pics that recess looks like it forms a sharp ridge at the bottom right section of the carb bore.

All I'm saying is if there is a sharp ridge there, it could cause turbulent flow along the floor of the carb bore. That, IMO would not be desirable.

Turbulence in the needle jet area would disrupt the pressure differential that causes the fuel to rise in the needle jet.

If the pressure differential fluctuated, then fuel flow would fluctuate as well.

Is that happening? I don't know...just appears to be possible from my experience flow testing

Larry, I understand what you're saying, that would definitely be a concern. I am still not sure what area you are looking at exactly, so I marked two spots in the photo.
A, on the inside of the bore, it is smooth there. I will stick my finger in there tomorrow, to confirm
B, on the outside of the bore, IIRC the transition is the same as it is along the whole top part of the bore.

Thanks for ALWAYS keeping me on my toes by the way

And this is a stock set. Would that flow any better in that area with the blind ports in place?

Sander,

It'a the A mark mostly that I'm looking at.

Generally speaking, where air flow is concerned, low spots and sharp edges can be flow killers.

So from the photo, it looked like both actually.

Air flow is a funny thing. Sometimes what your eye tells you is obviously good to remove is not good at all. Shortening valve guides is a good example of that sometimes.

Removing obtrusions, in general, can be fine but the shape of the end result can have adverse effects as well.

If the A areas doesn't look / feel like a good radius, just work it with some sand paper by hand until it's a nice radius.

The Keihin Velocity Stacks are designed to streamline that whole internal bellmouth area. Pop your's on the CRS31's you have and examine them. You'll quickly see the difference.

Here's also a photo to show how nice that setup is. Duplicate that as best as possible. It would probably render your current prototype stacks as design 1 and you'd have to redo them. But you know.... If you're going to put the effort into something....do the very best you possibly can. Just like you did on the rest of the bike