Appreciate it! I think I'm digging into her again this weekend ,so.....

It would be interesting to do a flow test on a Poor Mans Bak as opposed to other intake systems. Of course the Poor Man's BAK is not standardized as some guys make the unit into swiss cheese and others drill only a few holes. Some leave the holes open while others put foam filters in to control the cleanliness of the air getting to the filter. As Musky said the motor may not need all that air. I'm of a mind that the Poor Man's BAK may actually provide all of the air the motor can use.

I was thinking about this the other day. This may be wrong but if one knew: 1.) how much the volume of the cylinder was on the intake stroke, I forget the formula for the area of a cylinder but it won't be hard to find, 2.) how many times both cylinders fill at the maximum RPM of the motor (rpm times 2?), 3.) multiply the first by the second and you'll have an idea of the maximum volume pumped through the motor and a rough idea of the CFM (cubic feet per minute) the motor draws.

I've noticed people talking about using 600 CFM filters that are approximately the size of the Max Air system which looks like it has a similar surface area as the BAK. These units are probably overkill as far as air delivery. I've been interested in hot rodded chevy small blocks for a while and unless you are way over 350 cubic inches or building a high revving motor a 600 CFM carburetor will feed the motor. We're running 102 cubic inches with the stock motor. Too much air flow potential doesn't hurt as the extra capacity is never used anyway, the intake only takes what it needs.

The 40mm Mikuni probably can't use all of the air we're giving it. The conversion to the 42mm Mikuni is all about increasing the flow of air through the motor, more capacity is more power, higher RPM is more power. Power to the People! Sorry got carried away....

350 cubic inches 5000 RPM 600 CFM

102 cubic inches 4500 RPM ??? CFM

Brutha, You asking me to do the math first,.... I'm just a guy with a 1/2 drill bit! Seriously, I see what your saying, as I just rebuilt an edelbrock 600 cfm carb for my 318 dodge smallblock. Back to the R* airbox, I drilled 10 holes at 1/2 each. 7 in the back around the filter (K&N), and three in the front in the same area as the rear air p/u area. And I did not block these with any "filters" as the are in a safe place in conjunction to filter in case of rain.So..........

I know what you mean. I have 5 1" holes three on the edge of the box to the front and three on the trailing edge. My bike is acting like it wants to be rejetted. That's only around 4 1/2 square inches more intake area. With as many holes as you have you're going to have to rejet.

Is there anyone who posts on this forum and is "jet experienced" that lives near you? I've offered to buy Gearhead dinner or pay him to help me but it looks like I'll try it myself and get help if I mess it up. It really shouldn't be too hard to do it. The hard part is doing it right. It seems to be more Art than Science.

Brutha wrote:
I'll try it myself and get help if I mess it up. It really shouldn't be too hard to do it. The hard part is doing it right. It seems to be more Art than Science.

Famous last words.

Brutha wrote:
The hard part is doing it right. It seems to be more Art than Science.

With so many variables it is somewhat of an art, but one that anyone can do with patience.

Basic rules are:

- pick a starting point for the carb
- change only one thing at a time
- refine the main jet
- refine the needle
- adjust the PMS and if necessary, the pilot jet

Then decide you want different pipes or airbox and do it all over again.

Doc

I've pretty much got my carb where it SEEMS to be running well:
Altitude: 5,953 feet
DJ 175 Main
Stock #35 pilot
Clip on 3rd slot
PMS @ 2 turns
Speedstar K&N airbox w/billet backplate

The one thing (HA!) more I would like to do to the intake system is prt the manifold. Now, let me guess...I'll need to readjust everything, right?

RK<br><br>Post edited by: Roadkill1962, at: 2007/01/19 11:50

Roadkill1962 wrote:
Now, let me guess...I'll need to readjust everything, right?



I don't know if you will have to readjust everything but you will have to do some stuff over. That's why I ported mine at the same time I jetted. But hey. You get to pull it ALL apart again. Lucky dog.

Woof.

Have to strip it down anyway, considering the pile o' parts I've been accumulating for the 'winter upgrade months'. I just need to find time to put them on.

Damn, I hate it when real life gets in the way of hobbies!

RK

RK
If you ask my opinion, and you haven't . The stock mainfold is always going to be a piece - O - crap. I would get a Nemisis or wait until Ben has his tooling set up and running well. As lond as you're going to tear into it again you might as well put something good back in there. I'm waitng for Ben to get it running right myself. He designed his to use gaskets, not O rings.