Need help with Walbro Anatomy
 

I'm feeling pretty stoopid over here.

I'm converting a 50cc Echo short block for my brother and found a WT-463 for a pretty good price on *Bay. I believe these were found on McCulloch 46 and 49cc chainsaws. Anyway, without the engine in front of me Ican't for sure identify all the inputs. I was unable to get McCulloch's web site to cough up a manual (and believe me, I tried before exposing my ignorance). In particular, it looks like it has a crankcase pulse hole (#3) that I didn't expect. And I'm not sure what the little brass tube beside the mixture needles is for.

So, could those of you with some experience in this please indulge my ignorance and enumerate the ins and outs of this carb?

Many Thanks

KD

RE: Need help with Walbro Anatomy
 

#2 is the fuel inlet port. #3 is the crankcase pulse port. # 4 is the primer bulb port. I really dont know what number one is. it almost looks like it could be another pump inlet port but it dosent make sense they would have two of them. I am wondering if maybee it is part of the primer system.</p>

RE: Need help with Walbro Anatomy
 

Thanks Combatpilot - that's what I would have guessed. Ithought #1 was the pulse inlet from the crankcase when I was just looking at the pics (before I discovered #3). I wonder if some of the McCulloch models used a crankcase nipple and hose to #1 and just left #3 blocked? Looking at the Echo chainsaw manual, Ithink that's where the pulse tube hooks on to the original carb.

If so, that will make the carb spacer less complicated.

KD

RE: Need help with Walbro Anatomy
 

Yes, that's exactly right.  The #'s 1 and 3 are for the same thing; the crankcase pulse to the fuel pump in the carburetor.  Usually, when a carb comes with that number 1 fitting, the number 3 is a "blind hole".  It doesn't actually go through to the pump and the number one is used as you said to connect to a fitting on the crankcase.</p>

Number two goes to the fuel tank, and number 4 gets blocked off as it won't be used.  It was for a primer bulb in the original application.</p>

The fuel tank gets vented to the atmosphere; not to muffler pressure.  All hose fittings should be secured with twisted wire clamps or small zip ties, as the fuel hose will sometimes swell a bit when exposed to gasoline.  If there are any air leaks in the fuel system, the fuel pump in the carb won't work.</p>

AV8TOR</p>

RE: Need help with Walbro Anatomy
 

By the way, that Echo will make a nice engine.</p>

Here's a really good carb info page for you: http://www.zrcgf.com/pages/files/Tun...bro%20Carb.pdf

What did you have to pay for the Echo 50cc long block?</p>

AV8TOR</p>

</p>

RE: Need help with Walbro Anatomy
 

Ya I'm pretty excited about it. Ipaid $190 US + $23 shipping at Farmers' Exchange. It's the 1055.

Not bad for us Canajuns now that the USDis taking such a beating.

Thanks so much for the help and the link....

RE: Need help with Walbro Anatomy
 

That's a pretty neat website, thanks.</p>

No problem on the help from my end.</p>

Good luck with the project,</p>

AV8TOR</p>

</p>

RE: Need help with Walbro Anatomy
 

Be sure and seal #4 well or the carb will suck air though this hole and the regulator will not work.

RE: Need help with Walbro Anatomy
 

I usually solder it shut.  It's pretty easy.  Just hold a pistol type soldering iron on the side of the brass tube, and touch some solder to the open end of the tube.  It will solder/close right up.  Make sure the tube is clean first.</p>

AV8TOR</p>

RE: Need help with Walbro Anatomy
 

Here is another link I found useful.

http://www.drystacked.com/Walbro%20Carburetor%20Theory%20ebook1.pdf<br type="_moz" />

RE: Need help with Walbro Anatomy
 

Thanks everyone - great replies and excellent links. Ihave another question and I'm too lazy to start another thread:

Are the arms on the throttle and choke shafts plated or are they stainless steel? I've been soldering/screwing on longer arms to my carbs but Santa brought me a TIGwelder this year so I thought I'd give that a go instead.

Thanks again

RE: Need help with Walbro Anatomy
 

They are plated.  I usually grind the plating off and silver solder my arms to them...</p>

AV8TOR</p>

RE: Need help with Walbro Anatomy
 

Why would it matter? you can weld steel to stainless and stainless to steel. you can use stainless rod on steel and steel rod stainless. only problem would be is if its plated with zinc and if you cant tell that then you need some more welding practice. sorry didnt mean to sound like an a hole there lol.

RE: Need help with Walbro Anatomy
 

by now everyone knows that!http://www.rcuniverse.com/forum/js/f.../msn/47_47.gif

RE: Need help with Walbro Anatomy
 

Hmmm.

Just re-reading my original question. Seemed pretty clear to me. Unsolicited welding lesson aside, It matters (to me) because when I hit a plated piece of steel with a tungsten arc it goes fizz, contaminates the tungsten and I get a face full of toxic zinc fumes - in my experience. So if they are plated, I grind them off first. If they're stainless, I don't. If you can tell that they are plated by looks/smell/taste or whatever then good on ya. I can't so that's why I asked. That I need more welding practice goes without saying, but it is quite irrelevant to my reason for asking.

Thanks AV8TOR for answering my question.

RE: Need help with Walbro Anatomy
 

I am sorry if I offended. That was not my intent. I would have to know captn would open his pie hole. I dont think he can help himself. yea look at me lol.

Your right about contaminating your tungsten. I dont think your gona get anough of a wiff of zinc oxide to hurt ya. This sounds like a wifes tale but it does work. If your worried about getting sick after getting a good blast of zinc oxide then drink some milk and it helps prevent you from getting sick. I dont know how this works I just know from expereince that it does work.

As far as identifying stainles it is gona be non magnetic. not always though there are some grades of stainless that are magnetic but he magnatism is gona be a bit weaker than for steel. you can also tell by grinding on a small portion of it to see what the sparks are like. I really dout they would be stainless as they want to build as cheap as possible.

As far as not grinding it if it is stainless it is always good practice to clean up the area your gona weld anyhow. you will know its zinc coated as soon as you start grinding. it takes twice the heat to burn through the oxide layer than it does to melt the base metal. also do you really want that junk in your weld? if your tigging or even migging steel definatly clean off the mill scale. clean makes all the difference in the world.

Also you do know your supposed to grind your tungsten with a green wheel right? if you grind it on a wheel you grind regular steel on you will contaminate your tungsten.

RE: Need help with Walbro Anatomy
 

Combat...it appears that you have good knowledge in welding. Thanks for sharing that. Have a good day.....Capt,nhttp://www.rcuniverse.com/forum/js/f.../thumbs_up.gif

RE: Need help with Walbro Anatomy
 

No offense taken. Thanks for the tips. It makes sense that they would be plated now that Ithink about it.

I took a 30 hour TIGclass at our local polytech, and I've been tigging my face off since I got my welder. Mostly steel but I've put together a couple of aluminum mufflers with mixed success. My first practical experience with Zinc was when trying to weld a couple of nuts to the bottom of table legs. I thought Ihad ground off the plating but obviously not enough - what a mess.

TIG one of the most challenging things I've ever tried to master, but it sure feels good when it comes out like it's supposed to. Practice practice, more argon, practice...

RE: Need help with Walbro Anatomy
 

If you are concerned about zinc, but don't want to grind back too far, place a box fan behind you, so the zinc fumes are blown away, before they can be inhaled.  No quantity of metal fumes should be inhaled if it can be avoided.

Jack

RE: Need help with Walbro Anatomy
 

I know and its so much fun to do isnt it.