Project Fat Nikki

[t_g_farrell]

I put the nikki on tonight. It runs but has a high idle 1500 or so. Other than
that it seems to work pretty well. I will have to test drive it tomorrow.

The high idle may be due to the primary fuel jets being drilled out but I
didn't touch the primary air jets on top. That may make it overly rich at
idle. The idle fuel adjust seemed to have very little affect. When I looked
down the primaries during idle I can see fuel dripping fairly constantly in
both barrels but it doesn't look very well atomized. Could be just the low
air flow or is it a symptom of not drilling those primary air jets to match.

I also need to hook up the FBVS as that may be causing me some headaches
as well.

I don't think I have any vacuum leaks. I put a vacuum guage on the second
nipple from the front of the carb base gasket and it read a steady 10 and when
I blipped the throttle shot up to 15 or 20 and steadily returned to 10 as it
settled back to idling (at 1500 rpm). I expect if I could get it to idle at 750 rpm
that initial vacuum signal would be zero since thats the one for the advance on
the dizzy ( to my understanding anyway).

Of course I want to take this down to the Mitty this weekend and my wife
thinks I'm crazy. Maybe I am but its fun

[t_g_farrell]

I hooked up the FBSV and drilled the primary air bleeds to match the fuel jets.
No big difference. Also realized I forgot to plug the banjo bolt hole on the intake
manifold. Can you say vacuum leak. Plugged it with a bolt. Still has a high idle.

Took it for a test drive and it pulls pretty well and smacks you when you hit
the secondaries big time. Those need adjusted to come on a bit earlier but
thats minor. Won't hold idle and easily floods. Pretty sure its a vacuum leak
probably around the throttle body and/or spacer.

Definitely not taking the car with this carb to the Mitty. I may just swap the
Dell back on and go with that and come back to this at some later date.

[cshaw07]

Check for a vac leak where the primary throttle shaft slides into the throttle body on the linkage side of the carb. My sterling had a nasty leak there. There is a write up of mine stickied on 7club on how to fix that with an o-ring if you find a leak there.

I had the same problems with my carb when I got it. High idle, would stall when coming to a stop, under 1,800 RPM it would buck bad. Had to really know how to drive it to make it work right. I was at DGRR with the carb un-working lol For some reason too, my A/F screw has to be WAY WAY out but shes idling good now at about ~800RPM with 15in/vac at idle. Before it would do exactly what yours is doing, little to no vac under 1500RPM, but I used the third nipple from the left on the carb spacer.

[t_g_farrell]

Yeah I was going to check with some propane around the shafts. I remember
when I pulled the primary shaft out to cut it up it had some gooey stuff on the
shaft. I may try pushing some grease into it from both sides and see how that
works.

I won't get back to this until June, too much other stuff around the house to
deal with at the moment.

[t_g_farrell]

Oh well, a year later or more and I'm playing with this again. Put it on yesterday after
going through it again. I smoothed down the spacer gaskets on both sides and I think it
wasn't sealing well and causing vacuum leakage. I was able to get it to idle down around
1100 or so but it wasn't always stable. I wish I could remove the old gaskets on the spacer
and use the new ones that come in the rebuild kit, but those things seem to be glued on
and the space is plastic, so no bueno.

My float bowls are sticking and after shutoff and restart a lot of times it just pours gas
down the intake until I get them to settle down. So I need to pull the top and doctor
the float needles a bit or reuse the old needles and seats which I kept. When the floats
are working the level is on both bowls, so floats are adjusted good.

Also, I have the fuel inlet dead headed into the carb. I'm going to run the lines for the
return and hook up the return line and see if that helps. I think with the inlet dead headed
it is bouncing the float needles and sometimes sticking causing issues as well. Anyway,
it was a lot of fun playing with it. Had to stop when the engine started to overheat
cause I turned off my electric fans as I was trying to conserve battery. DOH!

I will say its very smooth on accel compared to a big 2 barrel like my Dell. I should be able
to just smash the go pedal without thinking once I get it idling good.

[GySgtFrank]

Originally Posted by t_g_farrell

My float bowls are sticking and after shutoff and restart a lot of times it just pours gas down the intake until I get them to settle down. So I need to pull the top and doctor the float needles a bit or reuse the old needles and seats which I kept. When the floats are working the level is on both bowls, so floats are adjusted good..

What kind of fuel pressure are you running? I've heard the Nikki likes a lot lower fuel pressure than most carburetors at 2 - 3 psi. Definitely following your progress.

[t_g_farrell]

I'm running the same I had for the Dell, 2.5 psi or so. I really think the new needles are the
biggest issue. I've heard others had problems with them as well.

[t_g_farrell]

Added the return to the carb and ran a return line to the tank. Also pulled the top and
massaged the new needle valves to fix the sticking. Noticed the new needles have a much stiffer
internal spring that the old ones. Anyway, turned the key the first time and my bowls
runneth over. Tap tap on the top fixed it for now. I may go back to the original valve or
needles anyway to see if that fixes it.

Also when adjusting the floats it seemed like they would settle differently every time I
measured them when the top was upside down. The drop was always consistent. I think
I'm seeing the needles bind. I'll try the old needles next if it continues to flood. Don't
trust the new ones much now.

[t_g_farrell]

Put the old needles and seats with the mesh filters attached. Put the top back on the carb
and the first time it ran over as before. I then started it up and looked at the float levels.
Front was 3/4 and the rear was like 5/8. Adjusted the floats until the meniscus of the gas
level was at the half way mark on both bowls. Then I proceeded to adjust the idle and the
air mix. The air mix has very little impact and I could only get the idle to be stable at
around 1100 - 1200 rpm.

I can tell its running rich by the smell and the temp. So I think my main jets are drilled
out too far. Not surprised by this so I'll have to drop something in there the right size.

Didn't take it out for a test run yet and it still sometimes drops through the idle and
wants to die after coming off of a sudden throttle input.

Tomorrow I'll see if it still wants to run over after sitting when the pump runs. Thats
annoying at best.

[t_g_farrell]

Turned the key this am to start the fuel pump and it still ran over. Something is sticking
after sitting a long time. The float levels before I did this were fine. So the floats should
have been closed anyway. Unless they are filling or absorbing gas somehow. They are old
but look ok except for some bubbling on the surface (no breaks).

I also now think my idle circuit is basically not working, perhaps due to air issues caused by
my changes. Its a puzzle right now.

I may have to get another carb and start swapping things like jets and tubes in and out
one at a time to see what happens.

[t_g_farrell]

Need to pull it apart and verify all the passages and holes. Pulled it off again.

I can switch carbs in under 2 hours now!

[djmtsu]

I need to try this with my carb.

Project Fat Hitachi. Lol

[t_g_farrell]

I'm going to put the stock primary jets and some of the other bits I drilled back to stock
and see how it goes then move forward again with the changes. Just to many unknowns
at this point to nail it down. I'll have to source another used carb, pullapart time!


I bet you can do similiar stuff with the Hitachi. Jeff20B on the other forum may have
done something like this, hit him and see.

[cookboy]

My primary jets are drilled to 1mm, all works well, idle can go as low as 700. But my ac likes 1000, so there it is.

[fbRXse7en]

http://www.youtube.com/watch?v=nrnoJMEWi_I