Topic: Won't fire

[76400F]

So after 4 months of completely rebuilding my 76 400F, the big day arrived to fire the old girl up for the first time in over 30 years. I consider myself to be above average on the mechanically inclined scale, but I do have weaknesses in the areas of electrical and carburetors. I turned it over and it would not fire. Have a great spark with new plugs, coils, points and condensers...etc., and I'm 100% sure the timing is good. The carb bowls are full of gas and I installed a complete carb rebuild kit. Can't seem to draw any fuel into the cylinders. I tried putting gas directly in the cylinders and still nothing. Just turns over with not even a sputter.

WTF am I missing here...it's got to be something blatantly obvious that I just can't see. I'm feeling like an idiot asking for help, but I'm at a complete loss.

[Swoop]

There are three basics
Spark, gas and compression.
You say you have spark....at the right time....assuming your cam isn't 180 deg. out.
I assume you have compression on a new build (stranger things have happened)
You say you have gas in the bowl, but none is getting through....I assume you mean that the plugs are dry.
I would start with the idle circuit of your carbs....checking the pilot jets and idle screw adjustment. What make carb kit did you use?

[76400F]

I honed the cylinders and installed new pistons and rings and lapped the valves. Very good compression.

The plugs are bone dry. Sprayed gas directly into the cylinder and couldn't even get a sputter, which I found strange.

I realize the cheap ebay carb rebuild kits (which is what I used) leave a lot to be desired, but it should at least fire, no? I reused the stock jet needle set. The screw adjustment is 2 turns as per spec.

With it being a wasted spark system, I can't see how the cam being out 180 degrees would matter?

[76400F]

Could valve adjustments really make that big of a difference? Looking back, when I set the tappets, it could be possible that I messed up which cylinder was compressing and which one was exhausting...

[Swoop]

i stand corrected on the cam issue.

[76400F]

I went down that road at about 8:30 last night Dowelpin! Haha, no worries...

There is definitely very good compression. And when I crank it with my hand over the end of the carb intake, you can definitely feel suction...

[76400F]

although maybe not as much as there should be...I'm going to try completely resetting the valves tonight...

[Joust]

I was there helping....sort of....mostly moral support.
When we put a palm over the carb, there is definite suction and your palm gets wet with gas, so there is inhaling going on without a doubt and the jets deliver some gas.
Why the plugs are not soaked is a mystery.
But even so, if spark is occurring on compression stroke, it should at least make a bit of smoke on exhaust when we spray into the cylinder unless timing is way off.
I'm bringing a timing light over tonight to make sure we are in the ballpark. I'm only in town for another day and want to see this puppy go before i leave.

[jonda500]

Did you dismantle the points cam/advance mechanism? if so the points cam might be 180 degrees out - if so, you can switch the blue and yellow wires and it'll go
John

[76400F]

During disassembly I actually broke the bolt that holds the spark advancer on so had to take it apart to eazyout it. Didn't think it was possible to put it back on wrong because it's pinned. If that's what's wrong, then I think we discovered that blatantly obvious issue. If that's the case, I'm never going to hear the end of it because my buddy suggested at least 5 times last night (for different reasons) to switch the blue and yellow wires going into the coils.

[76400F]

very clean, very dry plugs, no back firing, or any firing, whatsoever. VERY good spark.

I got the carbs off ebay from a guy out east. Mine where completely pooched. I'm wondering what the odds are that ALL 4 of them have the exact same problem that's causing them to block 100% of the fuel from reaching the cylinders. I've never seen this before which is why I'm stumped.

[76400F]

Going to get a compression tester tonight to be sure about the compression. Anyone know what reading is good compression for this motor?

[strynboen]

its the cam for ignision vho can be 180 aut..take the sentifugal regulator aut..and turn the cam 180...and Mount it Again..just pull the small 6 mm bolt right in center

[flybox1]

Yeah....nice one cal....beat me to it.
when you rebuilt the carbs, did you spray cleaner/air through all passageways?
air screws set a 1 turn out?
#40 pilots?
Clear tube the bowls to see if there is enough fuel covering the pilot jet, just like the picture calj posted. 

[flybox1]

Yes....but id want to do the easy spark test first.
Dark garage/plug against the head/hit starter...juuuust to verify 
Open the drain screw on #1 or 4....if gas drains out, its a good sign.
Shove a clear tube in bowl drain screw hole, hold/tape the tube next to the bowl, and turn on the gas...
Just takes a second 
If its not even close to the 3mm mark, then pull the carbs...you'll need to anyway to adjust this float height.
Diligently clean and clear tube all bowl fuel levels while on the bench.
Carbs done go back on till its all right.   As stated before, doing stuff twice scuks!

[76400F]

I actually brought one of my old bowls (with a broken drain screw) to work with me today so I can drill it out and put a barb on it to do the test you described. Does this really make that big of a difference (like I said originally, carbs are not my thing)?? I should mention that when I first filled them up they ALL overflowed gas. I took them all apart and just slightly adjusted the floats to the point where none of them overflowed. Could that have caused ALL of them to stop allowing gas through?

When I redid the carbs I cleaned them thoroughly, blew them out really well, then rebuilt them. The only thing I didn't do was take out the main valve (the cylindrical thing with the needle). I heard that the stock one is 100 times better than the aftermarket ones and not to swap them. Could the piece that slides into be clogged? Like I said, I cleaned and blew it out really well.

The slow jet is the aftermarket one. Should i put the originals back in?

Fly: What do you mean by "floats set a turn out"

Can't tell you how much I appreciate all the feedback...

[76400F]

After being totally frustrated last night I had my buddy hold the carbs up while I carefully removed the float bowl on #1. It was full to the point where once you took into account the volume of the floats and other stuff in there, it would have been very close to being full.

[flybox1]

I actually brought one of my old bowls (with a broken drain screw) to work with me today so I can drill it out and put a barb on it to do the test you described. Does this really make that big of a difference (like I said originally, carbs are not my thing)?? I should mention that when I first filled them up they ALL overflowed gas. I took them all apart and just slightly adjusted the floats to the point where none of them overflowed. Could that have caused ALL of them to stop allowing gas through?   DING DING DING!!!!  There it is!   YEEESSS!

When I redid the carbs I cleaned them thoroughly, blew them out really well, then rebuilt them. The only thing I didn't do was take out the main valve (the cylindrical thing with the needle). I heard that the stock one is 100 times better than the aftermarket ones and not to swap them. Could the piece that slides into be clogged? Like I said, I cleaned and blew it out really well.

The slow jet is the aftermarket one. Should i put the originals back in?  IF you can....definitely  Keihin #40's right?

Fly: What do you mean by "floats set a turn out"   Sorry....Corrected above...AIR SCREWS.  im a bit tired this am 

Can't tell you how much I appreciate all the feedback...

[flybox1]

also...pull out your main jets, and slide out the emulsion tubes underneath.  Those brass tubes all need to be spotless.  poke some brass wire through the holes to unclog them.  spray carb cleaner through them.    eye protection please. 

[76400F]

I knew you were going to say that Fly. That is a huge task and I was getting lazy near the finish line. It's the only part of the rebuild I didn't do because taking all the slides out are such a PITA.

Definitely #40 being used. I'll put the originals back in.

I dry tested the float levels with a float gauge and thought they were pretty close. Obviously not. Then again my eyesight ain't what it used to be and those needle valves are tiny.

The air screws are the ones outside the car right? I turned those out 2 turns like the manual said. I used the aftermarket ones for those too.

[flybox1]

No shortcuts bro! 
The farther you go OUT on those screws....the leaner you'll get.  2 turns out will make any stock 350/400 pretty lean.
Aftermarket screws here might make it even worse.  I cant say...havent been able to compare OEM vs Aftermarket.
Go with 1 turn out and your Keihin#40s.
Once the bowl fuel levels are right...fire her up!

[76400F]

OK, lesson learned. Didn't think carbs were that critical. I'm kidding. Not used to dealing with ones that were sitting in a field for 30 years...

The plan is to finish the rebuild properly, making sure the needle and emulsion tubes, low speed jets, etc, are spotless. Turn in the mixture screw 1 turn. Do a proper float level check and adjust to proper level (3mm below top of bowl).

One more dumb question: does it matter if the filter pods are on during the starting process?

Thanks again for all your help everyone.

[flybox1]

One more dumb question: does it matter if the filter pods are on during the starting process?

Thanks again for all your help everyone.

not dumb at all, but useful information indicating even MORE leanness in your carbs.

with pods AND 2 turns out AND adjusting your floats too high, you created your own leanness 

Do you have the original airbox/filter/plenum set?
what exhaust do you have?  stock, aftermarket, baffled?  please be detailed.
what size aftermarket pilot jets do you have?

[76400F]

Haha, you've both been such a great help! I don't know what is it about carbs, but they seem mysterious to me for some reason.

K&N pods - freshly cleaned and oiled with the K&N kit (not on during fire up)
After market stock main jets drilled to #80
All other jets standard size
Standard exhaust (2 unusable ones frankensteined into one very pretty one)
No muffler yet (didn't think it would make a difference for just trying to start it)

[flybox1]

Haha, you've both been such a great help! I don't know what is it about carbs, but they seem mysterious to me for some reason.

K&N pods - freshly cleaned and oiled with the K&N kit (not on during fire up)  If you oil them TOO much, it will further lean you out.  So, soak up as much of that red oil as you can, and go from there.
After market stock main jets drilled to #80  DOH!...drilled jets are too inconsistent for these carbs, but, likely you will need 85's or higher (depends on the exhaust you settle on)  Dont drill them any further.   BUY OEM Keihins @ jetsrus.com
All other jets standard size
Standard exhaust (2 unusable ones frankensteined into one very pretty one)
No muffler yet (didn't think it would make a difference for just trying to start it)  you're missing backpressure.  not as important at idle, but still, it should be there when jetting 1/4 to WOT throttle positions.