Been fooling around with carbs today.
Got myself an extra one as a back up in case I do something foolish
with the 'original' one.

On a normal set-up with this carb on a big HD it would run with a 180 main-jet ( = 1.8mm diameter hole)
I bored my main-jet up to 235 ( = 2,35mm diameter hole ...you get the point now...right )
in order to get it rich enough.
Nice.... except when reflecting on it and properly using what little brain I have left
there a slight problem:
The mail jet sits below a small tube that goes up into the venturi.
The hole in that tube is is big enough to flow the gas from the main-jet
except the needle is always "taking up room" in the hole , even at full throttle.
Calculated the 'effective area' (EA) of the hole

and the restrictive area of the needle at a position as when at full throttle.
Oooops: what was 'left' was an area smaller than the area of the main jet hole area.
My ham-fisted 'solution' to this was to bore up the hole in the little tube thingy

and raising the needle ( made possible by a DYNOJET aftermarket needle with grooves and a circlip )

Now to check the effective flow area, I put things back into carb
and again marked the position of the needle ( at full throttle )

Calculated again hole area and subtracted needle-at-that-position area.
...and hey !!! ...I now have an area bigger than the main jet even after boring it up to 3mm
to set it up for alcohol.
( The area of the former 2.35 main-jet hole was 4,2 sq. mm
the area of the now bored 3.00 main-jet hole is 7.06 sq. mm)
Now further down the system:
The bore of the float-bowl valve hole is 3.2mm so that's fine

but will the valve

restrict the flow ...as in will the valve be slightly 'in' the hole even when
fully open ( float bowl near-empty )
Dunno really, but I could measure the flow-rate, so I set up at test:
1 liter water in a bottle
Connect to carb
Hold up bottle while shaking about the carb ( as when running )
so float-valve would open/semi-open/close/open etc.

...and timed how long it took to flow 1 liter.
That took almost exactly 2 minutes, so:
At 160 km/hour ( 100 mph ) I would run 2.6 km pr. minute
or 5.2 km pr. two minutes
So I have 1 liter to run 5.2 km.
That probably doesn't mean a thing to you, but that's the equivalent of running
12.2 miles pr. gallon
That has got to be enough for a tiny 600cc engine even running on alcohol.
If not then I will just have to mix it with gas ( requiring less stuff to burn pr. mile )
This is hardly a rocket science exercise , but just my cross-eyed attempt try and set up the carb.
...............................
Now that the pocket calculater was hot in hand
I did a bit more calculating.
Wanted to know how many RPMs I ran at Bonneville.
I knew the speed ( just shy of 90mph ) the circuference of the rear wheel ( 2 meters )
the wheel and gearbox sprockets ( 40/22 ) and the primary sprockets ( 52/24 )
so it was a simple matter of going 'backwards'
and result was that I was running 4700 RPMs.
That's a good number and being slightly optimistic that this time around
I will run the same 4700 RMPs with a slightly stronger running engine
I've decided to mount a 25 sprocket on the gearbox
and if all goes according to plan ( ha ha ...as
IF ) running the same 4700 RPMs
on the little devil Saltbicquit, it will reach the phenomenal speed of 100 mph.
A fine round number, I'd say.
................................
New fancy and rather expensive headbolts and bigger hardened washers
from
ARP have been ordered.
Have a great weekend ya'all !
I hope I haven't bored you silly.