Difficulty starting a rebuilt 48 Panhead FL

[harleygreg]

Hi Guys

Prior to chroming and painting this 48 needs to run perfectly and I'm having problems starting her. She splutters for a few seconds but doesn't catch on.

I've never had the bike running and this is my first Harley so I need to check a few things;

Timing is spot on, it has the later auto advance unit, points gap is correct.
Spark Plugs are new Champion J12YC, gap correct, sparks ok
Timing gear marks all line up
It has solid pushrods, adjusted properly
Inlet manifold has been removed cleaned and new brass packing bushings fitted, greased - not pressure tested
Inlet nipple holes sealed - not pressure tested
Heads removed, valve seats look very good, but not lapped in by me.
Heads are from 1950, not 48.

I have two concerns - compression is only 60 psi on front and back cylinders, after about ten kicks, with oil in cylinders - this seems low?
The carb is an M-74, not the original, this has been cleaned, and set up as per the service manual, float level checked, needles set up per manual, no leaks - is the larger carb a problem?

Unless advised otherwise, My next steps will be to lap in the valves to increase compression and pressure test the inlet manifold - any other ideas?

Thanks for your support

Greg

[T. Cotten]

...Inlet manifold has been removed cleaned and new brass packing bushings fitted, greased - not pressure tested
Inlet nipple holes sealed - not pressure tested.... Greg

What are you waiting for, Greg?

....Cotten

[tfburke3]

You can check float level,but it is correct fuel level your looking for.I like to watch the bowl fill with it off the carb,but connected to fuel line while plugging the stem hole.Level,fill rate are easily verified.
Try richining g up the idle and hs alittle.
Tom

[BigLakeBob]

Are you advancing the cam when you check timing?

[ryan]

I also had that problem with compression in my front cylinder. I readjusted the valves and compression came up. I agree with the post above mine on timing an advanced distributor as I did it wrong early on.
Good luck!

https://m.youtube.com/watch?v=zFti-dUkSaU&t=24s

[T. Cotten]

When you are tired of chasing your tail, Greg,..

Please note when you bubble-test that the '48-early '49 silver-soldered steel manifolds are quite malleable.
All manifolds should have the flange ground flat, and the malleable ones occasionally need massaging first.

Note also, inside the bore of the attachment, the dot of silver paint sealer upon a dimple mark.
When the manifolds were assembled for sweating, a pronged staking device secured the flange to the rest.
These dimples occasionally leak.

The spigots are typically crushed from use, so please make certain your new seals are a very sweet fit.
The looser or out of round, the more likely you will destroy an inlet nipple rivet attempting to tighten them to stop bubbles.

...Cotten
PS: Valve seats shouldn't need lapping, if properly cut with modern equipment.
Lapping widens the seat, and embeds carbide into the bronze.

[kitabel]

In my experience, coughing without starting means it needs more gas, could certainly be a vacuum leak, but I don't like the low compression. You should have over 100 with oil on the rings. Low pressure means reduced vacuum in the manifold even if properly sealed. 1 tooth off on the cam (42 teeth) is really big - 17 degrees, it may be retarded, even 2 teeth, although I suspect your exhaust valve may hit the dome during overlap.
You can fake a milder/less retarded cam by simply making the intake valve lash really loose - but don't run it that way. If the CCP comes up immediately I suspect the cam.

[harleygreg]

Thanks Guys, this is good input on all aspects, I shall check all these and respond in a couple of weeks,

Greg

[harleygreg]

Hi Tom, interesting comment about fuel level, as I've checked this using your method, and set the float height (brass) as advised in the service manual/Palmer to 5/16" from the rim. However, it would be good to know what the fuel level should be, as this would be the relevant measurement?
Thanks
Greg

[Sargehere]

Ditch the brass float. They are heavier than stock and totally unreliable.
It's been my experience that sooner or later, every one leaks fuel, and sinks. Every. You are not the first to pull hair out trying to trouble shoot a brass float. The black plastic ones, either molded, like Rubber Ducky, or turned on a lathe, like Liberty or Mark Neberman's Chicken Plucker, never, ever sink or give trouble. White molded ones have a tendency to swell up after time (they all live in a gasoline bath, 24/7) and hang up on the interior of the bowl. Don't feel like The Lone Ranger; brass floats suck. Literally, suck up gasoline and sink.

[T. Cotten]

Hi Tom, interesting comment about fuel level, as I've checked this using your method, and set the float height (brass) as advised in the service manual/Palmer to 5/16" from the rim. However, it would be good to know what the fuel level should be, as this would be the relevant measurement?
Thanks
Greg

What service manual was that, Greg?

A Clymer?

For a ten gram India float, it takes at least a .375" setting to achieve a 5/8" fuel level.
For a twelve gram Kokesh, try .410", which nearly bottoms out.
Original cork and nitrophyll floats weighed five grams, including a pivotnut as captured in brass floats.

Linkert Model Ms never used a brass float. The book spec is 1/4", and I'm surprised Mr. Palmer would even address them.
(I don't get my second edition dirty much, since he deleted most of the good carb information in the first edition.)

Beware not all modern nitrophyl floats are created equal either!
Some weigh as much as brasses, and mass-produced varieties are known to swell, due to inferior obsolete formulae.

The latest and best formula is only available machined; beware of crude ones out there...

...Cotten

[tfburke3]

Hey Tom,are saying the correct fuel level is 5/8 from the top of bowl?
The indian manual says to set the fuel level-set the float 1/4 inch from the top,but doesnt mention the actual fuel level.I think I usually wind up with about 5/8 from the top or adjusted slightly lower if it overflows on the side stand.
Greg ,I would recommend one of Toms floats,even the brass screw and tube are right.
Tom

[T. Cotten]

My tests with different NOS floats (even DLXs) gave ~5/8", Tom!

And other students have corroborated, as you have.

My apparatus was refined many times to get a reproduceable result, and I adjusted the size of the lighter machined material accordingly.
(They are smaller in volume that OEM corks, and a lot smaller than OEM nitrophyl, thus allowing even more reserve.)

The level in the bowl is very important, as it must maintain supply to the holes in the main nozzle.
The float bowl is considered the first "circuit", before the idle and power circuits.
Mysteriously, the top holes of most nozzles are above 5/8".

....Cotten

[harleygreg]

Hi Tom

I missed this post. This says that whatever the float level height from the top of the bowl, it is the fuel level that is important, and that this should be 5/8" from the top of the bowl?

I think I need to check that!

Greg

[harleygreg]

Hi Tom, took bowl off and fuel level is at 5/8"!!!