What's up with tecumseh carbs?

[Fordiesel69 263]

So i've made mistakes over the years rebuilding these by not drilling out the soft plugs they provide in the kit.  In about 2005 I discovered this was not an option, I had to drill the plugs and clean all the little holes out.  Still no dice on some.  Then I went a step further, and did a hot water soak of muriatic acid and then an overnight mix of laquer thinner, acetone, xylene.

 

So I need to ask why a 1960s / 1970s kohler, or briggs carb can still work today for the most part, yet a tecumseh carburetor needs to be adjusted and rebuilt on a constant basis. It is just a piece of aluminum with holes and some brass and steel.   

 

The china repros online really seem to make sense but have almost identical flaws.  

 

[Achto 27,609]

I would take the @pullstart approach and just put a Kohler carb on your Techy. Problem solved.

[squonk 41,158]

[Pullstart 62,916]

38 minutes ago, Achto said:

I would take the @pullstart approach and just put a Kohler carb on your Techy. Problem solved.

Yup.

 

21 minutes ago, squonk said:

 

YUUUUUP!

[Pullstart 62,916]

In all honesty , it’s not too hard to put a Kohler style carb on.

 

 

[ebinmaine 67,642]

First let me just put it out front and I'm known Tecumseh carburetor expert.

 

I've been fiddling around with a carb on a 1968 HH100. 

I do understand the basic concept of carburation and I've had very good luck rebuilding Kohler carburetors.

I've done fairly well on a couple of old style Briggs updraft as long as I can get them to stop leaking fuel.

 

 

Thanks to @Stepney Spenser pointing me in the right direction I was able to find some info in different places online.

These are just things that I've read. Not in manuals. Not in bulletins.

I'd love to find some stuff that was put out by Tecumseh engines themselves but I can't find any...

 

What I've been able to gather is that the emulsion tube that goes up through the center was drilled in position at the factory. Once removed, it's likely not lined up again and will cause erratic, everything.

There was at one point in time, a replacement emulsion tube available. Apparently it had a groove made in a certain place which helped the gas flow or air flow or both, line up correctly.

Spenser mentioned to me that there is also a way to fix a stock originally emulsion tube by putting a groove in it.

I can't find a picture anywhere online about how to do that or where the groove should be but I can see that someone in the past put a groove or deepened a  groove in the tube that's in the carburetor that I have, right where the threads are.

See pic below.

 

Another thing I've read about the Tecumseh carburetors versus the Kohler carburetors is that Tecumseh took a very complex approach to what should actually be a fairly simple operation.

There are several additional very very small holes bored into a tech carburetor to be able to take readings of atmospheric pressure that a Kohler carb simply doesn't have.

ALL of them need to be not only cleaned but back to the correct size or things just aren't going to behave well.

 

 

I have a penchant for wanting to get this carburetor to run correctly.

This engine wants to run. It starts immediately. It sounds great.

 

I also don't want to waste a lot more time than I already have. I'm reasonably confident that I got it as clean as I can given the abilities and tools that I have and if I can't get it to adjust out then I'm likely going to go the route of cleaning/rebuilding a Kohler 8 horse carb and installing that.

[squonk 41,158]

Tecky carbs are like K car carbs. You adjust them one day they are fine. Next day start all over again! 

[Handy Don 12,237]

2 hours ago, Fordiesel69 said:

It is just a piece of aluminum with holes and some brass and steel.

Not as experienced as some members, but the one Techy carb item that seems to cause a lot of grief is the idle fuel supply passage.

 

Most of the ones I've worked on from the 60's and 70's for HH60 - HH80 have a floating check ball in that passage as well--no experience with recent after market carbs so I can't speak for them. Also, the HH100 and up use an outwardly similar carb but with different specs.

 

The main jet body usually has two threaded segments. Why? Because in between them, there is a tiny hole that feeds fuel into the separate idle supply channel alongside the main jet supply that goes up to the idle jet. Inside the idle supply channel there is often a captive "check ball" that helps vaporize the fuel. If you shake the carb that ball should rattle (float, choke, and throttle removed or held securely, of course). If it doesn't, that part is gummed or blocked (or your carb doesn't have the ball). (Note that if the float is adjusted to keep the fuel in the bowl too low then this passage won't get fuel even if it is clear--float height is critical and much easier to adjust!)

 

I read several posts on other sites to realize that there is no way to service that idle channel--it is factory plugged at the side, top, and bottom with only the fuel inlet and the jet oriface open.

 

I have a set of extremely fine (.015") hardened stainless steel "orifice cleaning wires", one has an "L" at the end that I use to poke through the passage between the main jet supply and the idle jet supply and also through the idle jet orifice to start. Then soaking with carb cleaner from both ends usually dissolves the gum and some light air pressure clears it out. However, if there is solid debris in there it'll continue to block the idle jet and you'll never get the carb to adjust properly (so, be sure the area around the idle jet screw is completely clean before removing it). I agree that Tecumseh should have put a Welch plug or screw cap on that passage, but they didn't. Some determined folk have drilled into that passage to clean it and then sealed it back up--I haven't owned a Techy carb yet that I couldn't clean or replace yet so I've not tried this.

 

My cleaning wire set is a similar to this one but with fewer wires.

Edited September 9, 2021 by Handy Don

[Handy Don 12,237]

32 minutes ago, ebinmaine said:

several additional very very small holes bored into a tech carburetor to be able to take readings of atmospheric pressure

Yes, the Techy carbs use a lot of fluid mechanics to govern the fuel flow. Like @ebinmaine, none of my reading (even in the Techumseh carb service manual) ever explained why)!

[stevasaurus 22,764]

Here is a good thread from Bob Maynard.

 

 

[ebinmaine 67,642]

1 hour ago, stevasaurus said:

good thread

Hey thanks for sharing that Mr Steve.

Not exactly what I'm working on but definitely helpful.

[stevasaurus 22,764]

You'd be  surprised how much help is in the "Reference" Section.  

[ebinmaine 67,642]

Just now, stevasaurus said:

You'd be  surprised how much help is in the "Reference" Section.  

Ha!!

 

If I only had half a mind to remember to look there once in awhile....

 

Good thing the rest of you folks are here to help me out. 

[Howie 886]

I think on that tube it had to do with how it was put in when manufactured, The torque it was 

tightened to aligned it so it was lined up or something to that affect. The tube you showed with

the groove cut in it was what was in the rebuild kits. With the groove the hole that was in there

did not have to line up exactly with the passage in carb. One could cut that type of groove in an

original one and it should work.

I really have had a lot of success over the years on these Tecumseh carbs, call it dumb luck or

whatever I guess. Biggest thing for me is that idle passage that gets plugged from water in there.

Never did understand why they drilled that like they did and then put that steel pin in there.