Intake Leak or???

[50Panhead]

I had problems with my Panhead running right and set it aside for a few years. This last winter I decided to get the old bike fixed. I knew I had intake leaks and finding this forum has been the inspiration I needed.

Long Story cut short.
I checked and rechecked everything.
Timing, Valve adjustment, Soap bubble tested the intake as per Cottons method, found leaks and fixed leaks Cotton rebuild the intake with peek seals, New float,Carburetor adjustment by the book.

But when I start the bike and bring the RPM's up it falls on its face. (see video)
I for some reason kept looking for the simple. But after several tests and observations. (main observation was it blowing back out the carburetor at high rpm when the motor falters.

I have come to the conclusion that the Valve Springs are Weak and they are floating out under load or high rpms.
I guess I'll have to pull the top end off again.
See my video on Youtube.
https://www.youtube.com/watch?v=bWEV...ature=youtu.be
We were using a timing light as visual reference that the ignition system was not failing.

What do you guys and gals think? Weak Valves???

[duffeycycles]

Looking at the timing light & listening ,it looks like ignition is not consistent-are the points shorting out as you rev?Does the coil give good spark?

[50Panhead]

Looking at the timing light & listening ,it looks like ignition is not consistent-are the points shorting out as you rev?Does the coil give good spark?

Please note the Kodak camera I used to video does not show what they eye can see. Timing light stays on although it appears to go off.
50

[duffeycycles]

Please note the Kodak camera I used to video does not show what they eye can see. Timing light stays on although it appears to go off.
Appears to go off when the bike is missing?

[Adam M]

Pop back thru carb is usually a lean condition, are you getting good fuel flow? did you pull the bowl and recheck? Are the bleed holes clear? Is it the correct throttle plate? ( also check Venturi) If the coil is suspect , swap it with known good one, replace the condensor ? Compression good? Leak down test? Start simple and go thru everything, that's what I'd do.
Adam

[50Panhead]

Pop back thru carb is usually a lean condition, are you getting good fuel flow? did you pull the bowl and recheck? Are the bleed holes clear? Is it the correct throttle plate? ( also check Venturi) If the coil is suspect , swap it with known good one, replace the condensor ? Compression good? Leak down test? Start simple and go thru everything, that's what I'd do.
Adam

Yes, Yes, and Yes. I have went over all the above several times. And get a load of this Installed new plugs and after some runs plugs are black with light soot. Sign of running Rich.

Again Bike will start with the first kick. Idles fine. When the RPM's are brought up to 2000 to 3000 rpms or there abouts bike falls on its face kind of like a rev limiter. Air stops sucking in the carburetor and fuel and air starts blowing out of the carburetor. I was hopping someone could tell me if that is a classic sign of weak valve springs where the intake valves are failing to close. I'm ready tonight to start pulling the heads back off. I'm almost 100% sure these are original springs. Bike is a 1950. I have owned it since 1973. In 1975 I had a HD dealer over hall it. I had the valves dressed up this last winter as part of getting her back up and running. I had been pledged with intake leaks. But Cotton helped me fix those. Now that they are fixed I find I have bigger problems.

Again I was hopping someone could tell me if that is a classic sign of weak valve springs.

[BigLakeBob]

Are you running orig hydraulic lifters? Are these failing and not the springs?

[50Panhead]

Are you running orig hydraulic lifters? Are these failing and not the springs?

Hydraulic push rods went away in 75. using solid alloy push rods.

[T. Cotten]

50Panhead!

I can't view utube but barely, but,...
Beware that aluminum pushrods get extremely loose when warm if you do not set them as tight as possible when cold, but still turnable with a rag on your fingers.
Its a thermal expansion coefficient thing. You only need enough compression to start: Alloy pushrods are a performance idea that even the performance companies reject.

Damage can happen, if sloppy; Particularly if the rollers aren't fresh.

Good luck!

....Cotten

[50Panhead]

50Panhead!

I can't view utube but barely, but,...
Beware that aluminum pushrods get extremely loose when warm if you do not set them as tight as possible when cold, but still turnable with a rag on your fingers.
Its a thermal expansion coefficient thing. You only need enough compression to start: Alloy pushrods are a performance idea that even the performance companies reject.

Damage can happen, if sloppy; Particularly if the rollers aren't fresh.

Good luck!

....Cotten

I understand Thermal Linear Expansion,
Calculus Physics about 15 years ago.


I have the push rods adjusted very snug (cold)

If its not the valve springs I'm at a total loss. I feel 99% certain that I have eliminated all other possibilities.

[duffeycycles]

I don't see it running high enough rpm to cause valve float.NOT VALVE SPRINGS.You say adjusted carb as book-set idle adj. low speed by turning in until it dies,back out 8 notches[approx]rev motor and adjust high needle to smoothest-recheck low to 8 notches above dying
This is close to actual setting with only minor adjustments from there
The black on plugs can be caused by poor spark as much as wrong carb setting

[50Panhead]

I don't see it running high enough rpm to cause valve float.NOT VALVE SPRINGS.You say adjusted carb as book-set idle adj. low speed by turning in until it dies,back out 8 notches[approx]rev motor and adjust high needle to smoothest-recheck low to 8 notches above dying
This is close to actual setting with only minor adjustments from there
The black on plugs can be caused by poor spark as much as wrong carb setting

Understand. Carb set just like you described. Good hot spark, new plugs, New points and condenser, Wire type plug wires. Points set As per manual, along with timing.

I'm using the Panhead Service Manual 1947 to 1957 Ridgid

[Adam M]

You said the bike wasn't running right , put it aside for a few years ,and now made your repairs. was it doing what you're describing before the repairs? If the answer is no, what did you change or do since? You said you did the carb and intakes, anything else?
Adam

[50Panhead]

Reading the shop manual....

Harley Davidson Panhead Service Manual 1948-1957 Rigid
page 82 and 83 Valve Spring Testing information

Quote from page 83 second paragraph.
" Because of the higher valve spring poundage obtained with the new springs, better valve following at high engine speeds results' Therefore, on the earlier FLH engines, when faulty valve actions is suspected as the cause of substandard engine performance at high engine speed, we recommend replacing old valve springs with new type springs. Use the following chart as a guide for ordering and using Big Twin OHV valve springs."

New Springs Part No. (outer) 18201-58 (Inner) 18202-57
Old Springs Part No. (outer) 18203-36 (Inner) 18204-36


I'm at my wits ends.

[Adam M]

Reading the shop manual....

Harley Davidson Panhead Service Manual 1948-1957 Rigid
page 82 and 83 Valve Spring Testing information

Quote from page 83 second paragraph.
" Because of the higher valve spring poundage obtained with the new springs, better valve following at high engine speeds results' Therefore, on the earlier FLH engines, when faulty valve actions is suspected as the cause of substandard engine performance at high engine speed, we recommend replacing old valve springs with new type springs. Use the following chart as a guide for ordering and using Big Twin OHV valve springs."

New Springs Part No. (outer) 18201-58 (Inner) 18202-57
Old Springs Part No. (outer) 18203-36 (Inner) 18204-36


I'm at my wits ends.

They are referring to FLH's....
Was the bike doing this before repairs?
Adam