running OK need tuning advice.

[pwrcat4000]

Data:

L20b out of 78 621with its hatachi carb, matchbox, & coil.  Cap rotor wires nkg plugs all about a year old.

 

Has been running great and cool all winter. Went to do my summer tuning, brakes oil change ect.

Looked at plugs the are all indicatve of runnung hot or lean (I think I may want to replace them with iridiums but want you alls advice on that)

Started adjusting idle and air fuel screw thinking it will make the air fuel at least at idle richer. ( don't know if that's right)

 I also noticed that the electric choke is always on? it seems like it, at least it is always electricly activated,  if I disconnect the power wire to it the car will stall without adjustment to the idle screw so I assume it's supposed to be connected and acting in that way, because that's the only way the truck will run.

Fiddled with all that stuff got it idling okay at the lowest possible RPM I could get just turned it by ear have not messed with timing it is still locked at the recommendations from other posts and of course it has been running great all winter.

 so the so the day after I did all that it was morning so time to start it and put the old truck back to work it was starting as it normally does I usually have to give it quite a bit of fuel to get it to go which is nothing new but what has changed is now the car truck will die if I don't keep the RPMs up until the motor is warm so I took it back apart and adjusted the idle screw up a little bit more this is where the problems that I need help with started.

The engine now idles extremely rough so rough it looks like it could shake paint LOL it still runs and it cleans up if I increase the RPMs checked my plugs again still look like they are all running hot/lean  noticed a Nick in the number one plug wire on the cap not the wire but the rubber surround it was throwing Spark when I disconnected the plug wire from the engine to see if I was having a bad plug wire or something so I switch that out with a new one. Adjusted everything again got it idling okay still a little bit rough but okay. Went to start it the next day everything seemed to be okay it is running of course the temperature in Kansas dropped about 45 degrees so I did not expect the tune to be very good in the cold weather as it was when it was 85 degrees. Still trying to figure out why the plugs look way they do. It is operating a little bit over the center of the Gage which is about where it has always been during the Spring and Summer I do think that I could improve the cooling because if I go into a headwind the temperature drops back to the middle like it does all winter long so I think an electric fan maybe something I want to try if you look at my old posts you can see that the cooling system is extremely clean inside and I have done many many things to make the system work as efficiently as possible as far as heat dissipation in the radiator and new water pumps hoses checking the bottom hose xcetera.

The problem

 it almost seems like it almost seems like it is surging randomly in the idle I have not been able to adjust it out but I have not played with the air fuel screw at idle maybe that would do some good.

So I am pretty Adept at tuning the damn thing. Thanks to all the advice and help from this forum. Feel like I have graduated from novice level to the possibly f*cking dangerous level.

Any ideas thanks in advance.

[mainer311]

If the plugs are white, it's running lean. If it stumbles a lot at idle, but is okay when you start revving it up, it sounds like idle is just really lean and it's starving for fuel. It could also be that your float level is too low. Where is the level of gas at when you look at the front float chamber? Have you changed the fuel filter recently? Sometimes they get junk in them and the bowl runs out quicker than it can fill. 

 

Also, take the air filter off and verify what exactly the electric choke is doing. If it's fully choked, it's going to idle really rough, but your spark plugs would look sooty.

 

The Hitachis are really easy to tune. All you need to set is the idle mixture and set the idle RPM after that. Otherwise, it's all just jetting. 

Edited April 11, 2019 by mainer311

[pwrcat4000]

Fiddled with the air fuel screw it's running better.

As for the float not sure how to adjust that. I had it stick down one time about a year ago, it would not start, took it out but did not adjust it... as far as I know. this carb has the circle glass but I do have the one off my 1600 carb which is all glass. I Replaced the filter in the fall as part of my tuning at that time.

[mainer311]

I like the all glass bowl cover better. It’s much easier to see, and has that etched line to show the correct level. The gas should fill to just above half way when working correctly. 

 

To adjust the level, you have to take the front cover off of the bowl, pull the float out (don’t lose the little spacer), and you bend the little metal tab that is part of the hinge. You’ll see that it’s actually the part that operates the needle valve. It doesn’t take much, so don’t bend it too much, and may take a couple tries. 

 

If the float level looks okay already, it’s probably just the idle mixture. 

 

Also, I’m not sure if you’ve already done so, but the stock spark plugs are usually gapped to 0.032”. With the matchbox and a properly matched coil, you can safely gap the plugs to 0.040-0.044”, which will help ignition. And don’t bother with iridium plugs, as they won’t gain you anything. Just stick with NGK coppers.

[banzai510(hainz)]

maybe clean the idle jet. but don't drop it.

 

I had a weber that had the electric cut off and I daisy chained it to the choke. I made a jumper to plug in the stock wire then it went to the choke and the lug had another wire jump to the selinoid.  So I needed the 12volts to keep the idle. I went back to manual later but its designed to keep the motor from dieseling like the later stocj Hitachi carbs.

 

time and adjust the mixture to best running condition.

as for plugs buy stock ones. I rarely change out plugss and dist caps anymore.  Got like 8yrs on mine

[datzenmike]

  Iridium are a waste of money on an old technology engine like the L series. You said yours are a year old so they are still good for tens of thousands of miles. Rather than change them maybe some adjustments?

 

Idle mixture...

Turn the idle down as low as possible so any changes are more noticeable. The idle mix screw is at the base of the carb on the valve cover side. The idle speed screw is to the left if looking at it from the passenger side fender. Turn the idle mix screw in or out in 1/4 turns. If idle is worse go the other way. There is about 3/4 to ont turn where id idles pretty good but drops off on either side. Set the mix screw roughly in the middle where the idle is strongest and fastest. Repeat but turning the idle speed back down and turn the mix screw in and out to find the middle of the best idle. You may have to do this a half dozen times till you can't improve the idle quality and the idle speed is about 650 to 750.

 

Take for a 20 drive with some wrenches and safely pull over but don't idle it. Check the plugs. Like new, bright shiny white porcelain is dangerously lean. Probably will barely run. Light creamy white is a bit lean but if runs ok will give good mileage. Light tan is about right for mixture. Dark brown to dry powdery black is way over rich and probably a black cloud following you. They will look like this if the choke is stuck closed.

 

Cooling...

If a '78 L20B, it will have a clutch fan. It is fluid coupled, so there is built in slippage at high speeds where vehicle speed is enough to cool the rad but spins faster at lower speeds. If the special silicon oil has leaked, the clutch will slip too much. With the engine off, try to move the plastic fan blades. If you can easily spin it, or worse the fan spins after giving it a spin, this is the case. What you should observe is that the fan is firm to move like a spoon in honey and stops as soon as you do. 

 

Electric choke...

There should be power to the electric choke at all times the engine is running. The choke relay can be a problem and often people disconnect it and use the idle cut solenoid for a new power source. The idle cut solenoid is that hex shaped thing beside the choke heater with the Red wire going to it. If you disconnect it it will shut off fuel to the idle circuit. This is what it's there for, to stop the engine when the key is turned off and prevent run-on.

 

[pwrcat4000]

Mainer

I agree what were they thinking glass is way better.

Banzai

I will use some cleaning juice in there see if there's an improvement.

 

Mike I feel like I should just text you when I have a question to save the Internet bandwidth. Lol

I will take you advice on the hitachi.

I am running the L16 pump and fan put it on b/c it fits the shroud w/o mods and I saw no temp differences so I just left it on there. Still think I need to go electric when I can.

My choke is wired to the coil so that is wrong for sure.

 

Still not in love with the temp's would be a proud achievement for me if I could get it to read middle all year round.

[datzenmike]

8 hours ago, pwrcat4000 said:

Mike I feel like I should just text you when I have a question to save the Internet bandwidth. Lol

 

 

But then others wouldn't learn anything from it. It's what bandwidth is for. 😄

 

 

Are the heater hoses looped together, by passing the heater?

 

[Charlie69]

Congrats on getting it running.

[pwrcat4000]

No hoses are connected to the heater core still some cool weather here i do shut it off though after it gets warm in the afternoon

[datzenmike]

This is what I mean. Are the hose ends connected together??? If they are, hot coolant from the head is being sent right back into the water pump and is by-passing the rad.  Find some way to seal the ends and block flow.

[pwrcat4000]

22 hours ago, datzenmike said:

This is what I mean. Are the hose ends connected together??? If they are, hot coolant from the head is being sent right back into the water pump and is by-passing the rad.  Find some way to seal the ends and block flow.

I don't think I understand. I have not messed with those hoses so I assume they are in the factory positions. Should I change them?

 

[datzenmike]

On 4/12/2019 at 3:25 PM, pwrcat4000 said:

No hoses are connected to the heater core still some cool weather here i do shut it off though after it gets warm in the afternoon

 

LOL read what you posted. Says... no hoses are connected to the heater core. Totally different if you punctuate it...

 

No, heater hoses are connected to the core... OR

No. Heater hoses are connected to the core.

 

 

If hoses are connected to the core ignore this.

[mainer311]

Correcting grammar on Ratsun. Might as well chase your own tail.

[pwrcat4000]

Yes, I'm doing it on my phone so punctuation is a low priority LOL

[datzenmike]

Well clarity should be a much higher priority. Lack of clarity wastes time and adds confusion. Take your time, this ain't Facebook swapping recipes. 😄

[pwrcat4000]

I feel bad about all the confusion. In my defense, I am fighting a killer cold. I will try to keep it 100% from here out.

[datzenmike]

No worries.