First Carb Rebuild...

[Mr. Big]

....was not a resounding success. M51 on my 45. Runs about 15 sec on 2-3 prime kicks and then dies. Did everything by the book I think. Before I take it off and go through it, what should I look for first?

[T. Cotten]

....was not a resounding success. M51 on my 45. Runs about 15 sec on 2-3 prime kicks and then dies. Did everything by the book I think. Before I take it off and go through it, what should I look for first?

Mr. Big!

Don't feel all alone.

The first thing I would suspect is not the carb, but the manifold.
Please review this simple diagnostic: http://virtualindian.org/11techleaktest.html

Good luck!


...Cotten

[Mr. Big]

Just swapped out the M88 that was on it and it ran like a champ so I wouldn't think the manifold would be an issue. Got all new stuff on it and set the Hi-Speed at 2 turns out and the Lo-Speed at 5 turns out. Oh, and thanks so much for the manifold tip.

[DaveAus]

Keep plugging away buddy.

Looking forward to finding out what the problem is

Dave

[Ohio-Rider]

After running for that 15 sec or so does it then puke fuel out of the carb?

[Mr. Big]

Nope. Just acts like it's out of fuel. Maybe bowl is hungup? Gonna pull it off tonight.

Hey Dave. Yep, me and you both!

[Ridermike]

Big, I had a similar problem on my 42 with an m-51. I’ll make a long story short and tell you that my problem ended up being the emulsion tube was varnished and gunked-up inside the carb body; it needs to draw air around the tube in this area. When I originally rebuilt the carb I couldn’t get the tube out without damaging it so I snaked some wire through it, saw no light around the venturi and called it good. Boy was I wrong. After the third or forth carb removal a little heat from a torch and a wooden pusher it came out and that “ You Big Dummy Feeling” came over me again.

[Mr. Big]

Dang! Pulled the carb off and blew it apart and cannot find anything out of order. I wanted to build a really nice carb so I started with a bare body and bought all NOS or OEM parts for it. Only thing repop is the hi-speed needle. Hmmm......guess I'll reassemble and try again!

On another note, is there a way to "repair" the detent ball for the hi-speed needle? Mine is pushed in and doesn't seem to have a spring behind it. Is there a method for removal and/or replacement?

[T. Cotten]

Dang! Pulled the carb off and blew it apart and cannot find anything out of order. I wanted to build a really nice carb so I started with a bare body and bought all NOS or OEM parts for it. Only thing repop is the hi-speed needle. Hmmm......guess I'll reassemble and try again!

On another note, is there a way to "repair" the detent ball for the hi-speed needle? Mine is pushed in and doesn't seem to have a spring behind it. Is there a method for removal and/or replacement?

Mr. Big!

Please review my last post, lest you chase your tail.
(Only after that variable has been absolutely eliminated can we then go on to concerns of the carb itself. And while the carb is off, make certain that the manifold's flange is truly flat. This can be achieved while installed by inking it with a felt-tip pen, and then dragging a flat stone across it. Few used manifolds do not need grinding.)

Please inspect to be certain that your replacement needle will actually reach the seat, inspect the seat of course, and that the needle is the wide taper, and not a narrow one for a fixed jet model.

On to the detente ball, just weld it out!
Grease up a new spring, and set the assembly with a 3/16" punch counter-bored to hold the ball.
Most only need the ball pressed in by hand, so be gentle.

Its a fifteen minute flat-rate operation.

(Note photo attached is a potmetal Schebler, which are far too brittle to ever be set with a mallet. One must gingerly retain it with the knob.)

....Cotten

[Mr. Big]

Thanks Mr. Cotten! I was gonna use my teeth but your idea sounds better.

And I will double check the manifold and make sure I have the correct low and hi speed needles in place.

[DaveAus]

Sorry to hijack your thread Mr Big but I have a quick question Cotten may be able to help me with.

I discovered a major manifold leak on my WL. As it turns out one of the manifold nuts was stripped so I decided to replace eveything (nuts, nipples, brass sealers etc).

One nipple came out pretty easily but I cant get the other side to budge. The easy side was riveted in the traditional manner however the other side has no rivet at all (I assume its been loctited in).

Any hints / methods to get the stuck nipple out while the barrrels are on the bike?

Thanks
Dave

[T. Cotten]

Dave!

Did you pressuretest each nipple separately?
If they did not leak, I would have urged you to leave them alone, as nipple replacement can be a very trying experience.

The only absolutely safe way to remove a nipple is to cut it and crush it. Backing one out that has threads that have been upset by stress of overtightening upon a rivet can destroy the cylinder threads on the way out.
Have you read the discussion I linked to previously in this thread?

The nipple had a rivet when it came from the factory. Please inspect inside for any indication of one. If the nipple has been replaced, there would still be a hole on the outside.
Nipples do not seal by their threads. They seal where they butt up against the cylinder, and the press-fit of the rivet.
If the rivet hole does not leak, then it is entirely dependent upon whatever sealer was used.

You will find other quite recent discussions about sealers for nipples on this forum.
We haven't found a perfect one, as modern fuels make them a lit fuse. Some are just longer than others.

Loctite can be loosened with heat (or modern fuels!), which is one of the reasons to avoid it, particularly on a Flatty.

You will find repairs very difficult in the chassis, as you will not be able to blast threads clean for any choice of sealer.

Once again, does the intact nipple pass a pressuretest?

....Cotten

[DaveAus]

Thanks Cotten,

They both leaked but one leaked more than the other. The one with the rivet leaked badly and the other not as bad.

The one that is stuck had a rivet in the barrel for appearance purposes only. When i felt on the inside there was no hole in the nipple. What I assume is that its been out at some stage and rather than put the nipple in they've put it back using some sort of adhesive and put the nipple in the barrel for appearance only.

Sounds like cutting it out is my only option and even then getting it sorted with the engine in is going to be an issue

Dave

[T. Cotten]

Dave!

If the nipple has no hole at all, then its threads are most likely intact, and backing it out should be safe.

I would suggest heating the nipple with a small concentrated source of heat, such as small brazing torch. This can even break down JB-Weld. Loctite would loosen much easier.

For safety's sake, it may be prudent to disassemble everything as much as possible.
Personally, I would have removed both cylinders as soon as the nipples showed bubbles.
Having them on the bench will allow the thorough cleaning and carefull observation that are critical to a successful repair.

Good luck!

...Cotten

[DaveAus]

Thanks Cotten,

I'll let you know how I go

Regards
Dave