HM Seris 3 Carb?

[TracMac]

Hi

I have Tecumseh HM80-155129B on a 1975-76 Vintage Craftsman Drift Breaker snow blower (model 536.90570)
Long story short version. Unit came in with work previous performed to it from another shop. The question I now
have is this a possible carb issue.

Got the carb apart for cleaning, (TC-631930) Its a Series- 3 Fixed jetted type Main, but has adjustable
low speed needle mix screw. The carb had a Idle port access welch plug recently installed and dented in.
fortantly the body is okay after removing it to inspect it. Along with other noticeable re-assembly errors.

my question is this, Is there supposed to be a (BALL PLUG) @ the bottom of main fuel column? for idle circuit column
to be sealed @ the bottom? Also there is NO Fuel Feed hole drilled inside the main column ( Threaded Area where the
bowl nut threads into) to feed the idle column on this type of CARB. But there is an outside hole drilled into Idle circuit
column almost halfway up from the bottom.

UnLike the traditional (Series 3) Adjustable Carbs that have an (idle feed hole drilled inside) the threaded area to feed
idle circuit column. The idle column always has a sealed ball plug to seal off the column. My gut feeling this is possibly
missing? on the carb I am currently working on. There is a service carb available (TC-631957B) but I questioned its
replacement interchange due to idle circuit porting differences. Since Tecumseh has not stamped anything in repair
parts since 2008, I questioned the real service parts for correct interchanging, since a lot stuff is becoming rapidly
obsolete & trying to kitbash parts to work on existing engines is not always guarantee it will work correctly.

I'm not the type to throw parts @ it to see if it works, but like finding the TRUE CORE of the problem then fixing it.
I am hesitant in taking the service carb route, without visual proof that it will interchange correctly. Let alone I don't
have an exact example to look @ to verify my suspicions of the missing ball plug.

Any input would be greatly appreciated.

[motorhead64]

Hi TracMan
I have used the 20 dollar replacement carbs available on the Bay for that engine with very favorable results. One has worked well on a Craftsman 9/29 for the past 2 winters. This winter was a pretty good test! MH

[bgsengine]

Got the carb apart for cleaning, (TC-631930) Its a Series- 3 Fixed jetted type Main, but has adjustable
low speed needle mix screw.

Are you sure it is a needle? have you had it out completely? Several versions are also done up with those "needles" actually being pilot jets.

The carb had a Idle port access welch plug recently installed and dented in.

generally that's how a welch plug is supposed to be installed?

fortantly the body is okay after removing it to inspect it. Along with other noticeable re-assembly errors.

my question is this, Is there supposed to be a (BALL PLUG) @ the bottom of main fuel column? for idle circuit column
to be sealed @ the bottom? Also there is NO Fuel Feed hole drilled inside the main column ( Threaded Area where the
bowl nut threads into) to feed the idle column on this type of CARB. But there is an outside hole drilled into Idle circuit
column almost halfway up from the bottom.

now THAT depends on a number of things including whether you have an actual mixture adjustment screw, or a pilot jet that "looks like" a mixture screw for one thing..

It also depends on what angle they drilled the jetting - I have seen some that go *crosswise* through the main nozzle column and a tiny ball plug on the opposite side from where expected... also I have seen some where the ball plug is in that idle columm you refer to but deeply recessed (need an otoscope to see it) I'll check this afternoon if I happen to have a used carb laying in the scrap carb pile (almost time this year's ebay auction listing to clear off the ol' carb bench - probably have 60-80 carbs laying in the scrap bin) and if I do I'll get details for ya.

I'm not the type to throw parts @ it to see if it works, but like finding the TRUE CORE of the problem then fixing it.
I am hesitant in taking the service carb route, without visual proof that it will interchange correctly. Let alone I don't
have an exact example to look @ to verify my suspicions of the missing ball plug.

Any input would be greatly appreciated.

You havent described what the nature of the problem is yet either - could it be not a carb problem? air leak? timing? valves? who knows?

However, ball plug is not *necessarily* missing - maybe someone here has an exact carb to yours (Post the MFG casting number off the top of the carb body for a definitive I.D. of the carb)

[KE4AVB]

You havent described what the nature of the problem is yet either - could it be not a carb problem? air leak? timing? valves? who knows?

However, ball plug is not *necessarily* missing - maybe someone here has an exact carb to yours (Post the MFG casting number off the top of the carb body for a definitive I.D. of the carb)

He somewhat did. It had been in another shop with work being preform on the carburetor so he trying to straighten that out first just to get to find out what the real problem is. I have had undo others work just to get the real problem a few times here too over the years and that can be harder than fixing the original problem.

The diagrams does show it having an adjustable idle mixture screw and replacement also has the adjustable idle mixture. As for idle circuit being different on the replacement carburetor that should not matter as long as the exit points are in the right place. I would think you could have a linkage setup differences that might need resolving as the original carburetor setup is listed as being only used on two versions of the HM80.

[TracMac]

Okay, to answer some of the questions asked

Engine is a (HM80-155129B) Serial 5226D Date built 8/14/1975 (just incase it
was overlooked from beginning of last post.)

1) It a Series-3 NON EMMISSION CARB The stamped Casting number is (588 5H12)

2) It has an adjustable low speed needle (Pointed Tip) Not a pilot jet type.

3) The High speed is a (Fixed jetted bowl nut) because of the application thats its used on.(Snow Blower)
There is LESS THAN A (1/4 Inch) of clearance between the (Carb BOTTOM) & Snow Chute Directional Control
Lever that runs directly below the Carb. This is why it not a fully adjustable Series-3 CARB!

4) The Welch plug was put in using a Smaller Punch DENTING it into the center of it
practically restricting some the of idle & Transfer port feeds. When I extracted it
the plug nearly fell out ( Not Sealed Correctly)

My original ? was (Is there a ball plug) suppose to be at the bottom of the idle Well column?
ON THIS PARTICULAR CARB?
I don't see any drill marks from someone attempting to remove it, as I have seen this in
the past. But doesn't mean the ball could of fell out. I have seen loose 1's in other carb castings in the past.

The complaint was it would not stay running or run for a short period of time.
and New Points & condenser plus a welch were installed @ the last recent repair shop.

Here is what's been discovered
1) New breaker Points are BENT! Stationary contact was not fitted into breaker box pin hole.
2) Condenser mounted upside down ( wire pigtail facing up) Flywheel rubbing it.

3) A Resistor Cap in place of the original plug boot( Cap off a snowmobile or ATV application) used in place of
a new plug boot. Good way to suppress spark.

4) New fuel line cut to short ( Was pinched in several places) and stressing the (Fuel tank nipple) causing
it to partly close .

5) Carburetor welch plug dented in the center (Loose), Throttle plate installed backwards the 3 o'clock marking
facing inside the venturi. Possible missing ball plug in idle well column?

I have not done a compression test yet, but its seams real good when pulled ( No Guarantee I know) But
will check it, most likely taking the Head OFF for examination since its an older model engine.

Before I started to do any work on it, & Before I found some of the existing problems stated above. I did get a chance
to hear it run, Hard starting ,didn't not run very well, coughing, surging and some black smoke, occasional back fire.
maybe 3 minutes tops of run time before it quit.

[bgsengine]

2) It has an adjustable low speed needle (Pointed Tip) Not a pilot jet type.

Sharp, long taper point? (Most likely) - if so, would mean it is a *fuel mix* adjustment - if the point is more "blunted" , more likely is an air mix adjustment (with the associated metering rod) and they are "bass ackwards" from what many techs are used to for adjusting - you turn screw IN to richen the mixture. (which has been a clue many a time reviewing some other shop's work when the engine's running rich.. they try to lean it out by turning screw in and make it worse)

3) The High speed is a (Fixed jetted bowl nut) because of the application thats its used on.(Snow Blower)
There is LESS THAN A (1/4 Inch) of clearance between the (Carb BOTTOM) & Snow Chute Directional Control
Lever that runs directly below the Carb. This is why it not a fully adjustable Series-3 CARB!

Thought as much - Might be worth while checking the bowl nut jet number (most have a number stamped in the nut for the jet size) and compare to the correct part number - easy enough to swap around a bowl nut that "it screws in and looks the same" and yet may be the wrong jet size.

4) The Welch plug was put in using a Smaller Punch DENTING it into the center of it
practically restricting some the of idle & Transfer port feeds. When I extracted it
the plug nearly fell out ( Not Sealed Correctly)

OK - "dented" is sort of a misleading term - most welch plugs when installed right during service will have a slight dimple in the center - they work by "flattening" the plug by punching in the center which expands the plug's sides to grip the hole.. but from your description, it sounds like whoever installed it *overdid* that quite a bit (which would explain why it could fall out)

My original ? was (Is there a ball plug) suppose to be at the bottom of the idle Well column?
ON THIS PARTICULAR CARB?
I don't see any drill marks from someone attempting to remove it, as I have seen this in
the past. But doesn't mean the ball could of fell out. I have seen loose 1's in other carb castings in the past.

I honestly could not say - Like you I have seen those ball plugs fall out and rattle around in the bowl - what I was suggesting is a closer look because I have seen then where the ball is actually pressed in much deeper in that channel - you'd have to look with magnifying glass or otoscope - and I have also seen them where the jet holes were drilled cross-wise through the main nozzle tower and the ball plug is on the the side.. I dont happen to have that specific carb laying in our carb box that I can find, so can't tell ya for sure. - But from your symptoms, I would tend to say it is *unlikely* to be missing - you also mention a hole or jet drilled in the side above the float fuel level? - if it is definitely above fuel level it may be an air bleed (float height set right, by the way? - They are NOT set level/parallel to body , but a little "down" when carb inverted) and in those cases that little hole is the actual idle fuel feed - which if float is set wrong, will be sucking air instead of gas.. but that'd mean it was lean, and yours isn't...

The complaint was it would not stay running or run for a short period of time.
and New Points & condenser plus a welch were installed @ the last recent repair shop.

Here is what's been discovered
1) New breaker Points are BENT! Stationary contact was not fitted into breaker box pin hole.
2) Condenser mounted upside down ( wire pigtail facing up) Flywheel rubbing it.

Seen that so many times.. not a surprise actually nowadays with inexperienced newbies who may have never seen a set of breaker points in their life before...

3) A Resistor Cap in place of the original plug boot( Cap off a snowmobile or ATV application) used in place of
a new plug boot. Good way to suppress spark.

Made me chuckle.. obviously you plan to fix that too.

4) New fuel line cut to short ( Was pinched in several places) and stressing the (Fuel tank nipple) causing
it to partly close .

amazing what a low-paid "professional" with a wrench in his pocket can do, innit?

5) Carburetor welch plug dented in the center (Loose), Throttle plate installed backwards the 3 o'clock marking
facing inside the venturi. Possible missing ball plug in idle well column?

loose welch would cause lean mix typically backwards throttle plate, how would it even run? usually they will only fit up one way.. maybe things are a bit worn out in there or wrong plate installed?

I have not done a compression test yet, but its seams real good when pulled ( No Guarantee I know) But
will check it, most likely taking the Head OFF for examination since its an older model engine.

Before I started to do any work on it, & Before I found some of the existing problems stated above. I did get a chance
to hear it run, Hard starting ,didn't not run very well, coughing, surging and some black smoke, occasional back fire.
maybe 3 minutes tops of run time before it quit.

surging and black smoke? sounds more like a rich running engine with a governor issue (or a misfire is possible too) but from what you describe, amazing it would even run.

It gets real confusing - since you indicate so many things that would normally cause it to run really lean, but black smoke means it is getting too much gas (or not burning it all)
My advice - I would start by fixing the easiest and obvious problems (ignition and fuel lines, etc) and leave the carb for last - and after fixing the obvious mess-ups in the carb, (welch plug, check float adjustment, etc) make sure and do a static governor setting first and then diagnose your surge, if still present... as far as the "in-doubt" seemingly missing ball plug - perhaps a close inspection may reveal the plug is one of those belonging deeper down the idle circuit hole, not at the end like many of the more common ones.. but if there's doubt and things still dont run right after fixing the other problems, either way you pretty much need to grab a new carb which I'd recommend anyway, if everything else seems to be running right. - Basically fix the ignition, make sure governor is set right, and if it seems to run even halfway decent, slap in a new carb and don't even bother trying to fix what is most likely a colossally screwed up carburetor hacked together from someone's loose parts on the carb bench.. I wouldn't even bother wasting the time trying to fix the carb beyond throwing a 99 cent welch plug at it, if even that (I might re-form the welch plug with a rounded punch and a 3/8 6-point socket and just re-use it to at least get er runnin' before splurging on a new carb on what might end up being a basket case)

[TracMac]

BS Eng & everyone

Sorry for the delay, Thanks for the input, its appreciated .

I was also surprised too, when it started and run. How I don't know? with a resistor
cap boot on a set points & condenser magneto engine. I think that when it misfired
multiple times with a spark tester inline ,along with a resistor cap in line loaded
down ignition system a little too much. Tried with out tester inline and ran about the same.
This May of Caused some of the rich discharge, believe me its a real sick Tecumseh in need of help.
Not the smoothest running engine, but its not the first time for these type problems encounter
in the past years ether.

More to come, later this week.

[TracMac]

Update

Sorry for the wait, hears what was done to get it running again.

I got suspicious about the valves and Found (Zero valve clearance on exhaust valve, & only .004 on the intake valve).Clearance
should be .010 for both. I Did a complete valve job, with new gaskets. Replaced points & condenser, Checked the stator
plate timing, within specs, no adjusting needed. Cleaned the carb, inserted the missing ball plug into the bottom of the idle well
column. Replaced and sealed idle circuit welch plug that was an earlier problem. The throttle plate stamped line position
was set @ 9 O'clock when found. I reset the T-plate back to the correct 3 O'clock position. Finished carb with a 631021B repair
kit. The Carb No# is for reference only, Tecumseh (No 588) and uses a fixed jet Main bowl NUT that's stamped with a number 55.
For anyone that is or find themselves working 1 these units.

Engine was still hard starting when fixed, after trying to eliminate possible carb issues? and double checking my work. problem was found
after remembering the symptoms of bad points, just hearing it run, and certain sound pattern for those long time tech's in the field would
know what I'm talking about. After finding out the new points I installed, it had a somewhat deformed point contact that was loose on breaker arm side.
It was not loose when I installed them, defective part from the get go. This was a Genuine part (TC 30547A) The points would float and
causing hesitation when the engine was accelerated Immediately causing it to run enough out time, but still would run with a slow acceleration
of the throttle cable. Installed another Genuine contact set and Engine started on first pull. Runs Smooth with plenty of power and no hesitation when accelerated
Immediately from the throttle cable. I didn't want to leave this post unfinished, in hopes it would help some else down the road.

Thanks for everyone's input its appreciated.

[38racing]

I know problem is fixed. I was surprised that you say it has fixed main jet because it is on a snowblower. I have 80s blowers and even a 92 that had adjustable main jet. As for the idle jet I have both fixed and adjustable. To confuse a future owner (not likely to be one) I had a problem with a fixed idle jet not running right. If I backed it out it ran ok so I replaced it with a variable needle from another carb.

[TracMac]

Would never thought of that 1, using a needle in place of pilot screw.
This is where knowing all about the carb your working will pay off or
help you in seeking a compatible replacement need be.