2G Carb Question

After getting the distributor situation fixed-up and getting it run, I am trying to tune the carb. As I hadn't really let it idle much so I thought things were running okay. Wouldn't start yesterday or today due to flooding issues. I pulled out the plugs and dried them out and allowed the carb to dry out, and finally got it to restart and ran it at higher rpm until things cleaned up. Went to adjust the idle and it runs best with idle screws all the way in - as soon as I begin to open up the idle screws, it chokes out too rich. So, even at low rpm I am obviously getting some sort of fuel flow bypassing the idle circuit.

I did the rebuild myself with a kit from Mike's - but I barely understand the 3 circuits. I put in new idle screws which was a bit of process to get the correct replacements. I guess I could try with the old screws and see if its a screw issue, but I think its an issue with fuel going though some other circuit - maybe leaking through or around the main jets, or leaking around the power valve? Any troubleshoot techniques or should I just pull it all apart.

Here is my rebuild info:
Fino's 1970 mini build thread

 

This is from Mike's website - so starting here:
My carburetors are running rich at idle

Here are a few things to check. Not in any particular order.

Float level.
Bad float. For brass floats, heat some water and immerse the float. Any bubbles indicate a leak and the float should be replaced. Nitrophyl floats should be replaced. The only test is to weight them.
Fuel pump pressure.
Power valve is not seating, allowing fuel past it when in non power mode.
Fuel is leaking past needle & seat. Be sure you cleaned the old gasket material off completely.
Main discharge check ball is not seating. Hold the ball down with a brass drift punch. Put fluid (like mineral spirits) in the pump well. Press the accelerator pump down. You should feel some pressure. If the ball is not seating, fluid will be siphoned at idle. You an seat the ball by hitting it gently with brass drift punch and hammer.
Run thin wire down all small passages, especially the venturi.
Seat was damaged when installing. Too much pressure on the seat when adjusting the float is a common problem. Inspect the viton tip closely for any marks.

The accelerator pump works well - get a good dual stream of fuel. Plus when its running on the main jets it works great. Took it around the block and it was perfect - no hesitation and it even idles fine as long as the screws are closed. I pulled the top of the carb and I reset the float as well as inspected the needle - Needle looked perfect and the float was off a bit but that didn't solve the problem. It still runs well when the idle screws are all the way in. So I just pulled the entire carb off and broke it into its 3 parts - all the gaskets look good in terms of not blocking any passage ways etc.

Three things that concern me - but will have to wait until tomorrow or later:
1) the check ball at the bottom of the accel pump was loose. I think that ball is supposed to be seated? I remember there are two check ball - one is in the main passageway, and the other is in the accel pump well at the bottom? I need to review the rebuild proceedure and verify if I need to seat those correctly.
2) I will very closely examine the new idle screws and re-verify these are exactly what I took out. Maybe they are not closing off properly and allowing fuel around them even when all the way in.
3) Wondering if something with the power valve and power piston is not working correctly in terms of sealing. I do have the little gasket that goes under the power valve, and the power piston is much freer than it was before the rebuild, but maybe something isn't right there.

 

Julius - I am learning carbs as I go so what do I know. Just to verify you accelerator pump is functioning, look down the carb throat and move the throttle up by hand - you should see two nice streams of fuel shooting into the throat. If not, you have a pump problem for sure.

 

Link - Post #28

 

I ran out of time and patience last night - but will pull the power valve out and check to see there is no junk behind it or any issues with the gasket/washer thingy. Everything runs absolutely perfect with the screws all the way in - drive it around as nice as possible and even idles well. Gotta mean I am getting fuel through some other path way. As I have thought about, I don't think its an issue with the screws (but I will check) because opening the screws causes a rich misfire (chokes it down) and will eventually kill it - so as I open them its getting more fuel. There are only two other passageways - the powervalve and the main jets. The main jets work through vacuum (there is no opening or closing of them - always open) - so shouldn't be a problem in this case? Not sure how the power valve works in combination with the power piston. I assume when the piston pushes down on the valve needle it opens the valve? Could the valve not be closing for some reason?

 

It's possible.

There could be left over crud in the way... It doesn't take much.

 

That is exactly the problem I am having right now...I am actually out of town near you in west yellowstone...but as soon as I get back will see what i can learn. I 100% know that it didn't do this before I rebuilt everything...When I first got the jeep, I spent a quite a bit of time getting the carb working well, and it really worked perfect. Idle screws were out just under 1.5 turns - I even used a vacuum gauge to confirm what me ear was hearing. I think I am getting flow through, or around the power valve. When I first attempted restarting the engine after the rebuild I had a few backfires through the carb due to my distributor issues - so wondering if that caused some issues like maybe sticking the power valve open or damaging it. I took it all apart, cleaned under the power valve as well as the valve itself - a new valve didn't come in my rebuild kit so I had to re-use my old one and put it all back together. The power piston seems to move freely, and I am checking with Mike's carbs to see if I can get a new power valve. Thinking its also important to make sure the power valve needle and the bottom of the power piston are all aligned correctly when the top cover is put on the top of the float bowl. Be back home in a week and hope it will work...

 

Some of the 2g carbs require a check ball at the bottom of the accell pump well and some do not - mine does. It needs to a small, light aluminum one as it has does not activate based on vacuum but rather based on the 'head' or weight of the fuel in the fuel bowl. It allows fuel into the pump well. If you are supposed to have one, and do not, it can cause too much fuel to flow into the pump well and then it may overflow into carb causing a rich fuel condition (this according to mike's carbs video etc).

 

Allright! Think I got it working correctly now. I pulled the carb off and took it all apart and essentially put it all back together (using the same new rebuild parts I got from Mikes Carbs a couple months ago). Again, the main issue I noticed was NOT when driving or accelerating, but only at idle - it ran better at idle with the idle screws all the way in and thus I knew there was some sort of fuel bypassing the idle circuit to keep it running. A few things I focused on that may have helped solve the problem - I did it all at once so not sure which was the exact solution:

1) I made sure to seat the stainless steel check ball in the main passageway that is under the spring under the the little 'T' clip hold-down.
2) I made sure the aluminum check ball was in the correct place under the accell pump in the well, but did not seat it as that could damage the aluminum ball.
3) Made sure to clean under the power valve, and to clean the power valve and make sure the needle was free (thanks Focker)- this is the one I think may have been the real problem as the needle in the PV seemed to be a bit sticky. I am thinking fuel was flowing through the PV when I shut off the idle screws. I actually ordered a new one for $10 but since it took a couple days I got it working with the old one before it arrived.
4) Made sure the power piston moved freely (which it did) and properly aligned above the PV needle when the top cover was put on top of the fuel bowl.
5) As I was not as concerned about initial engine break-in at this point - I made sure the throttle screw was turned way down so as to not be getting flow through the main jets and could truly test the idle circuit. As I adjusted the idle screws, I had to turn the throttle screws down even more - so as Ron mentioned that may have also been part of the problem.

All the while I kept a timing light on it with the vac advance line plugged - as I turned down the idle screw it definitely lost a bit of advance timing so I think that confirms the rpm's were a bit too high and the mechanical advance was kicking in just a little. I would recommend having a good tach hooked up while doing this (and I will probably do it as I am fine tuning things with a vacuum gauge as well).

thanks all!

 

Quick 2g question: Do the main metering jets use a washer of any type? The old jets I pulled out didn't have them (but wouldn't trust a PO). And when I installed the new jets I did not use any - and don't think any of the rebuild kit, directions or vids from Mikes Carbs mentioned them either. But there is one under the PV so was wondering if there should be any under the main passageway metering jets.

2nd Question: I have some confusion on setting float based on FSM and the different types of floats. My FSM says 1 3/32" (1 5/32" for emission equipped) to the bottom of the float - but the pic shows a different type/shape of float where the seam is not in the middle of the float but rather near the bottom (which is up in the pic of course). With my copper float - should I go to the seam like the pic shows below, or should I measure to the bottom of the float (up in the pic) which would increase the amount of fuel in the bowl? I am a little concerned that I might have the float a bit too low causing a lack of fuel miss when under constant high rpm.

thanks

 

1 - I don't recall any washers.

2 - See if these help Post #49

 

That thread is why I am using the middle seam...just wanted to make sure