aftermarket OEM carb choke lever modification for the HS40

markus

Well-Known Member
#1
Here's a recent problem I just had to deal with and thought I'd share what I came up with. Building a 1970 HS40 and the application calls for the air cleaner mounted high for fender clearance and the use of a Tecumseh/taylor dog leg muffler. The carb that the customer supplied with the engine for rebuild has issues, one of which already being that the choke lever was incorrect and damaged on it as well as something issues internally.

So I wanted to use a new replacement carb. While I am not in love with them, and you have to tear them down and go through them out of the box unless you want a leaker, you gotta use what you can get. Big issue is they put that long doofy choke lever on it. That's done so you can manipulate it yourself and make it work on various applications. Most people don't care about that and 90% of time this stuff is going on power equipment or something to that effect where the look does not matter.

In this case it does, plus the lever needs to be in an accessible, safe area if possible.

I tried a few different variations/twists, but I cant get it to look good and even come close to clearing with that style header:


in some cases you can simply swap the lever out (it depends on the detent and spring location that locks the lever in selected position). Unfortunately the Chinese carbs are in the wrong position for the levers that the HS engines used, to make matters worse they don't have a hole precast in the body to move the spring to like some of the OEM Tecumseh carbs did.

So here's what I did, I took an old carb that has both hole positions pre cast into the body, removed the spring stop and the choke lever. Broke out a "post-it" note and a small punch, stuck the post-it on there (sticky side on the carb body to help keep it in place), rubbed it with my finger to inset/show the holes a little, and used the punch to knock out the holes:



I transferred the post-it over to the new carb body, I left the springstop on the body still and carefully slid my pattern over top so It would help ensure I got the hole marked in the correct spot, also used the punch in the choke arm hole to verify alignment and then used a spring loaded centerpunch to mark the spot to drill:



Important thing to remember is that spot on the carb body is thin, so mark the depth for your drill bit and be very careful! ( I just bottomed it in the hole of the OEM tec carb and taped the bit):



Good idea to double check that depth on the china carb and adjust if necessary, I did not have an issue but I would not doubt they vary a little depending on who is making them.

With all that done, remove the existing spring and transfer it to the newly drilled spot. Use a good set of pliers right at the base (clean good teeth that grip all the way on the spring surface) and then twist out. Keep the pliers all the way at the bottom, you can only swing about half a turn so bottom the pliers each time you reset and try to keep it all as straight as possible when doing that and you can usually get it out in reusable condition:



I did find that even though my drill bit was the correct size, with a little wobble while drilling (was using a hand drill) made it a looser fit than whats ideal...its tight enough that I think it would be fine, but I'm gonna dab it with some adhesive inside the hole just to be safe. If you drill holes better than me (99% of the population probably can-put a drill in my hand and I start shakin' like Janet Reno :wink:) and the spring is a tight force fit, thread it like you did taking it out keeping the pliers as close to the bottom as you can so you dont kink spring.

Finished product:



The other BIG problem with this was finding that particular choke arm!!! I had to do some digging to find the right one, as they are NLA!! So please remember to try and salvage what you can off the old carbs before tossing them in the garbage! And let me know if you have any to get rid of :laugh:
 
#2
Thanks for that, Sensei Markus!

I will look for choke arms like that in my pile. Pretty sure I've only seen those in the Master Parts manual or Microfische though. If I find any they're yours.
 
#3
Interesting. I have yet to run in to issues like that, but the specifics of the air cleaner location and exhaust style obviously needed some ingenuity for the choke to be accessible and function well. Nice work.
 

markus

Well-Known Member
#6
Thanks for that, Sensei Markus!

I will look for choke arms like that in my pile. Pretty sure I've only seen those in the Master Parts manual or Microfische though. If I find any they're yours.
I spent the better part of the week digging around in my boxes trying to scrounge up some of them, I only found 2 to work with, Hopefully I can find a few more as they were very common for the early HS's in both slanted and standard configured engines.

here's the part number and a good shot of what it looks like on its own (from oldmowerparts.com site) please let me know if you have any I can buy!!!

 
#8
I spent the better part of the week digging around in my boxes trying to scrounge up some of them, I only found 2 to work with, Hopefully I can find a few more as they were very common for the early HS's in both slanted and standard configured engines.

here's the part number and a good shot of what it looks like on its own (from oldmowerparts.com site) please let me know if you have any I can buy!!!

I will do that. I had a new garage door installed and had to haphazardly move all my junk. Tonight I will see whats in the box of small parts I threw together.
 
#9
I was having the exact same issue. After I tried different bends on the lever, I just stuck mine in the jaws of a vise and straightened right up. It seemed to be the only way to get it to clear. 100_1618 1.jpg
 

markus

Well-Known Member
#10
I was having the exact same issue. After I tried different bends on the lever, I just stuck mine in the jaws of a vise and straightened right up. It seemed to be the only way to get it to clear.
What I do when I am doing an HS with box muff or an aftermarket carb on an H series is bend the arm straight up, give it a half twist on the parallel behind the air cleaner backing plate and then a 90 right above it. Gets the lever out of the way of the exhaust and comes out looking pretty clean/stock looking still. Heres one like that on an H35 I recently rebuilt:



 
#12
Man, that thing looks beautiful !!

The twist. The twist !!

The twist might be just the answer. Every time I tried a 90 just above the air clearer, it hit the spark arrestor in the "almost" off position.

I might even have to order another one of those cheapo china carbs just to experiment with the "twist". I'm afraid to try it on the present one now because I think I might have cold worked the metal with my previous "experiments".
 
#13
Yes, that twist is awesome. I wish I saw this thread before I bought 3 carbs with the wrong choke arms...

I'll have to remember "the twist" in the future.

Danford1
 

markus

Well-Known Member
#14
To add to this, It almost looks like the replacement H50-H60 carb may accept that choke lever out of the box :shrug: The throttle shaft though would have to be swapped out as well since it actuates in a different manner. The downside is it looks like it might only come with the inlet fitting that pops straight out. Thats doable on remote tank apps but no ideal if your running the engine mounted tank. You cant get away with a spring inside the fuel line to keep it from kinking like tecumseh did in the 60's/70's on some of the engines...the fuel these days just flat out buggers it up to fast.

Snowblower Carburetor H30 H50 H60 5HP 6HP TROY BILT Tiller Tecumseh Carb 631067 | eBay

The other difference I see which I dont know if its good or bad is the bowl vent is routed into the carb bore instead of out the side. Technically I would think that's not a bad idea- no dirt to get into the vent hole, and is also somewhat filtered and sheltered from the elements. But I would think it may pressurize the bowl a little, I don't know if that would be problematic on an application where the throttle is always getting worked :shrug: I have never tried using one yet, anyone run one of these carbs on a mini bike/kart application yet??
 

markus

Well-Known Member
#15
PART 2.....converting the H40-50-60-70 to HS

ready for Part 2 :shrug: As stated in my last post I was thinking the medium frame H50 style aftermarket may fit the bill without having to mod the spring location, so I went ahead and ordered one up. For under $13 bucks shipped I figured I'd give it a looksy :laugh:

compared to a stock HS40/50 mini bike/header style carb (what I need to replicate):



The choke detent spring is in fact in pretty much the right spot (the Chinese drill it in a little closer than it needs to be to the center, but the clock position is good)

the other things though that dont match are Bowl overflow/vent runs into the inside bore of the carb rather than a pee hole out the side. Of course the throttle arm assembly is incorrect as well and wont mesh with the HS standard linkage so that has to be conveted as well.

The H50 does have a larger bore in the center where it chokes down, I measured the 2 when I pulled the arms and butterflies out.



that might not hold true for all of them or against the older, original carbs, it has been machine bored though the center so they may vary that. Nice that its opened up a bit, but again you get that restriction on the inlet from the overflow tube (that could be taken out pretty easy though and just drill out the side) I also compared the high speed/bowl needle assy's and the aftermarket H one has some larger inlets to it to take in fuel compared to an oem One I pulled from the one nice original HS carb.

swapping over to the HS throttle and header style choke lever was not a problem:



While its not a big deal if your running a remote tank, I could only find this style carb with a straight out the side inlet. that is kind of a pain when its on a self contained engine where the line has to snake though the shroud, It doable but it does not want to cooperate too well usually. It also clearly does not look correct for that application.

The inlets are pressed into the body of the carb, I hit the emtpy body with a touch of some heat for a few seconds and then grabbed the inlet and gave it a twist with some pliers while it was securely mounted in the vice. Anytime I have a dead carb I yank whatever will come off it and try to save it so I have few inlets and will use whatever suits the build best, since these press in, you gotta kinda use your discretion on sealant. Just a quick test fit of this one and I am gonna want a dab of something to make me fell better its tight but I could do it by hand with some force, most older carbs I have to press them back in with the vice.



Hows it work....well I dunno yet :laugh: As you can see I was in test fit mode today soon as the mailman dropped it off with some other goodies I found last week. I still need to go ahead and "rebuild" the new carb, test the float, and all that good stuff. so I will detail out the throttle and choke levers and set that all up when it goes back together and get it tested out soon, I think it should be fine though.
 

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