what happened to my mid range power?

[freak_leg]

Ok guys, to i messed with the beast a little bit today. Found out i cant move the needle under the top cover of the carbs, however I found one of my fuel lines had a small kink in it, flowing but not alot. I moved the lines around and went for a ride. Just a short one around the neighborhood. enough to wind out first gear and it didnt seem to lug down. Could a slightly restricted line cause this? or is this just a fluke?

[Incubus]

I don't think a kinked fuel line would affect only midrange power. That would most likely cause an issue with top end power when the bike is using the greatest amount of gas. The carbs live off the fuel in the bowls, not the fuel flow from the lines, so whatever empties the bowls the fastest would be the most affected range.

I still think you have a needle issue. Did the needles appear to be shimmed? That would most likely have been the cure for straight pipe midrange fuel starvation.

JMHO.

Patrick

[petejw]

Did you find out what size main jet
your running?

[freak_leg]

I did not find out what size my main jet is. Would you mind letting me know how i would go about figuring this out? sorry like i said. limited carb experience.

[Rickrod3]

I did not find out what size my main jet is. Would you mind letting me know how i would go about figuring this out? sorry like i said. limited carb experience.

The only way I know is to remove the jet and read the number off of it.
I'm a student of Carbs as well as I understand it
Upper range about 6k to red line mostly affected by Main jet.
4K to 6K needle height.
3k to 4K float height
below that pilot jet.
HTH
Rick

[petejw]

remove the float bowl,
the main jet sits on the top
of the tower, and screws into the bottom of the emulsion tube,
it should have a number stamped on the top or the side,
that number is the size of the main jet.
let us know what size they are and we can go from there.

[petejw]

heres a link to Wildkats
excellent write up 'Carbs 101"

http://www.xs11.com/forum/showthread...t=carb+diagram


the first pic shows a carby with the bowl off
with the main jet exsposed.

[psycoreefer]

I've got the same stumble, always hits around 4.5 - 5.5, same cold or warm, same with the choke on or off. I've got stock jets, stock float level, stock air box, mac 4-2 pipes and needles raised one clip. I'm really interested to see what solves your problem. FYI if I drop my needles to the stock position I have really bad stumble below 3.5K.

[petejw]

hey psyco,
looking at your signature and the sounds of your
problems your probably running rich,
the stock jets are 137.5,
by raising the needle your also running it on the rich side,
if a stock air filter is fitted and your running the mac exhaust
you wouldnt need to change it from stock.
are the emulsion tubes the exact same ones as the ones you
replaced or are they an aftermarket part?
what size pilot jets are you running?

just a couple of things to think about.

[WMarshy]

Your bike/carbs should have adjustable needles... The '78 and '79 carbs have adjustable needles so this might be contributing to your probelms. Maybe someone put on the later style carbs. If they did, we will be able to tell from the jet sizes... Take a look and report back to us.

[psycoreefer]

[hyjack]

hey psyco,
looking at your signature and the sounds of your
problems your probably running rich,
the stock jets are 137.5,
by raising the needle your also running it on the rich side,
if a stock air filter is fitted and your running the mac exhaust
you wouldnt need to change it from stock.
are the emulsion tubes the exact same ones as the ones you
replaced or are they an aftermarket part?
what size pilot jets are you running?

just a couple of things to think about.

pete, I don't know what you mean, my signature says I have 137.5 mains and 42.5 pilots, stock sizes..,


Ok, so I updated my signature after your post to make you look crazy.

Anyways I am running stock size jets right now. My signature was just a little out of date. And yes the emulsion tubes were NOS from yamaha, but I did replace the center ones with the "richer" ones for the outer cylinders so its running the same all across.
I know that I shouldn't "need" to tweak anything for my setup and yet I've been through everything I can think of and I have but three options:
1. Run the needles one clip up and deal with a stumble at 5k-ish
2. Run the needles stock and +4 size idle jets, and carry extra spark plugs in case I sit to long at a traffic light because if fouls plugs at idle (BTW this is what the PO was doing)
3. Run completely stock setup carbs and have an off idle through 3.5k stumble that is so bad that the bike is unridable.

I choose number 1, because it is the least "hassle". If your really interested I had a thread a while back about the issue with all my findings and what everyone suggested, you could read through it and see whats been tried, I really would like to solve the issue but I'm just plain flat out of ideas. Really my working hypothesis is that the PO either cut the slide springs or drilled out the holes in the slides, or both, causing it to lift early and/or fast and requiring the strange setup, but every time I ask, no one seems to know what the length of a stock slide spring is, or what diameter the holes in the slides should be, and I don't have the money or desire to buy another set of "early" style carbs just to find out.
[/hyjack]

[bikerphil]

every time I ask, no one seems to know what the length of a stock slide spring is, or what diameter the holes in the slides should be

Psyco, I just checked this for you on my 79 Special. Spring length is 91MM, slide hole diameter is a #42 drill bit (.0935"). HTH