leaking intake nipples

[rousseau]

After finally finding the problem with my hard starting, poor idling motor I now need help. I have a serious vacum leak around the intake nipple on the front head. The threads in the head are not in the best of condition. I'm guessing they were cross threaded at one time because the first couple of rows are missing, and the rest are barely there except for the deepest part. It takes some finesse to get the nipple started in the head but it does screw in and will tighten down. I am however, reluctant to press my luck by tightening it more and destroying what threads are left.
Is there some type of "modern " sealer that will stop this vacum leak? Permatex? Teflon? J B Weld? I am open to all suggestions.
One thing I am sure of is that I'm not the only member that has seen this problem on the knucks! PLease Help!

Dennis Rousseau

[jww]

If truely fixing the problem is not an option, i've had good luck with a product called moto seal II made by permatex. It is gas and oil resisitant and temp. limit is 500 F. Kinda hard to find around here, bought some off of the net a while back. Only color available is white, but if done neatly doesn't show much.
Good luck
johnny

[koanes]

AMCA member Tom Cotton has some nipples that he had made with a slightly O/S thread. Might be just enough to give you a little more confidence when tightening. Most important is the sealing surface, which is where the lip that sticks out from the head meets the nipple. Tom also has some seal rings made from a softer and more pliant material to replace the brass that requires much less torque on the nut to seal. Check out the Flathead Power tech forums for more info. If you search the archives there you will find mucho info. Please feel free to email me if I can be of any help.

[T. Cotten]

But last time,
I was only successful after installing a
full oversized nipple that was supplied by....


Confess!


(I do not want to be the only one who shamelessly self-promotes around here.)

[Paps]

Cotten....You ain't never replied with the intention of shamelessly promoting yourself. Every reply I ever saw you make anywhere was directed solely for the purpose of saving another owners bike from severe damage and from the feeling of humiliation the owner would aquire from not making sure of no intake leaks when they had a chance to prevent such damages. Thumbs up for Cotton in my book!! Paps

[rousseau]

I have come to realize that when attempting repairs, you have to be somewhat of a Detective. You search for "clues" to find the problem.You then try to find what caused the problem. I have decided that the threads were damaged when someone removed the nipple without properly removing the rivet. The threads are bad from the rivet hole out. Now the rest of the story.
In my previous post I neglected to say that this Knuck is a "Chopper/Bobber" and I am using the aftermarket nipples that adapts to the o-ring(panhead) type manifold and a modern carb. Please forgive me those of you who consider this an act of blasphemy. So Johnny is some what correct when he ask if a true repair was not an option. It also eliminates Cottens "oversized" nipples. It sounds like the heat resistant permatex may be my ticket. Or maybe Cotten could share a little more info on the Seal-Lock Fluid -Weld he mentioned on the Flathead power site.

[T. Cotten]

Rousseau!
You are still in deep water, even with an O-ring conversion.

Fluid-Weld is good stuff: http://silver-seal.com/ but it will NOT solve the problem if the threads are gone.

Careful rivet removal is important of course, but even then the threads of the original nipple are often distorted from the peening installation, thus tearing their way out if unscrewed. This is why I instruct to cut and crush nipples for removal in the VirtualIndian tech piece on this subject:
http://virtualindian.org/11techleaktest.html

The most thorough and practical way to be a "detective" is to inspect with dilute dishsoap at ~15 psi. You will be quite fortunate if you can goober in a loose nipple that will pass this test successfully. And then have the goober withstand heat and vibration, cyclic expansion, and modern fuels as well.
(Even o-rings do not last like they used to in P4gas.)

So in the end, you may well get enough bubblegum on it to stick long enough to make you wish the repair was "correct". Beyond eliminating the need to re-rivet, the o-ring conversion only depreciates a vintage machine.

[Bill Pedalino]

Intake Niplpes

As an alternative to dish soap, you might consider a product called 'Snoop'. I comes in handy squeeze bottles and it's manufactured specifically to detect even the smallest leaks in pressurised mechanical systems. We used it in the diving industy to detect air and helium leaks in deep diving systems. Just a drop on even a tiny leak causes a large net of bubbles that stays for at about 5 minutes. It works much better than dish soap.

I don't remember who manufactures it (possibly Swage-Lock), but you can probably track it down at a good mechanical ball valve or Swage Lock fitting supplier.

[koanes]

Bill, I do have a couple of O/S oring style nipples left if your threads proove to be too badly damaged. Intallation requires that the head be set up on a millining machine, the hole bored, and then tapped with a 1 13/16" - 20 tap.

[HarleyCreation]

The late (and great) John Nowak from Harley-Davidson told me story about those old time compression ring manifolds on a Knucklehead.

During WWII he rode for the Harley factory all over the country on Army business and said he had a factory bike where the rivit came loose on the head/manifold and was dancing around like crazy. He rode it that way for a long time and the bike was VERY FAST.

Finally, Nowak took it into the Service Department on Juneau Avenue and the guys fixed it for him.

Guess what?

He said the bike never ran as strong or as fast as it did when the rivit was loose and dancing around and that he could never figure that one out.

===================
Harley's Origin and More!
At the Creation

[AdminGuy]

Because it was running lean, maybe intermitently -would be my guess.

I've seen that 0-ring convert locally. My impression was the bike was devalued a good chunk due to this hack.

I've fallen deeply in lust with 39 Knuckles. If you go pee at a gas station and find a scout bobber where your 39 knuck used to sit, that would be my doing. I'll see you down the road about 3-5 miles. Hee-hee..... and it's heel to go.

1,2,N,3,4.

[LouieMCman]

I got you beat Paul...my Indian is a 5 speed.......
1,N,2,N,3

Louie

[AdminGuy]

hee-hee-hee... good one Louie!

[HarleyCreation]

Originally posted by AdminGuy
Because it was running lean, maybe intermitently -would be my guess.

Yes, probably the reason.

Originally posted by AdminGuy

I've fallen deeply in lust with 39 Knuckles. If you go pee at a gas station and find a scout bobber where your 39 knuck used to sit, that would be my doing. I'll see you down the road about 3-5 miles. Hee-hee..... and it's heel to go.

1,2,N,3,4.

The 1939 paint job is the BEST and still with those nice looking winged decals. IMO they sort of ruined the Knucklehead by fitting those fat 16s and a clunky tank badge in 1940 and it got even worse in 1941 with those metal strips.

Somewhere, somebody from Harley-Davidson told me why they built the 1939 tranny that way, but I don't remember now what the reason was.

Anyone know or hazard a guess?

The 1936-39 EL Models are about the nicest looking "classic" bikes imaginable.

My 2 cents.

===================
Harley's Baby Years!
At the Creation

[AdminGuy]

I'd like to know also! Why in the middle? Was this just ANOTHER H-D experiment gone horribly wrong? Hee-hee....

Maybe the thought process was to have a smaller gap between 1,2 for smoother around town police work?

Carl has a burg, cream 39, http://www.carlscyclesupply.com/photos.html
Vince in CA has a Blk, cream. I rode with Vince in SD and informed him that his 39 may go missing for a short period of time when he's not paying attention. His is set up really nice. It's a runner!