Hs40 carb replacement

Bbqman

Active Member
#1
Hello my motor, hs40 55408c is having issues with the original carb. I have talked about it on other threads. I am trying to find a replacement. All the ones I see have the butterfly with the holes for the governor linkage left of center. My oem carb has the holes right of center so the governor arm pushes the butterfly open not pulls. Can someone help me. This carb is going to be the end of me, lol thanks in advance. Picture is of my original carb for reference IMG_20210213_130259083.jpg
 
#3
What I do with those chicarbs is cut a small strip of brass with a hole drilled in the end for the linkage and solder it to the top of the throttle with the hole where it should be. Never had one break yet.
 

markus

Well-Known Member
#4
the revised # service carb can still be found to replace that particular one with the correctly drilled Idle circuit, mainjet, and passages. its Tecumseh part number 631795a. Tecumseh Service carbs do not come with the choke lever, has 2 holes to position the detent spring (depending on lever used for your application) so you transfer yours onto it and the throttle shaft is made so you can bolt on the correct bellcrank to the top for your application. If it does not come with the bellcrank, simply file off your OG from the shaft and screw it on.

If your looking at a carb that has a pull style throttle lever on it, its for a larger engine application and the circuits and bore will be different, and in the Chinese carb world they are usually too large internally already compared to the OEM's and don't function well.

@ELT Do you need one of the mini bike specific HS 631625 choke levers? I have them in stock, but they are pricey $25 + the ride
 

Bbqman

Active Member
#5
Well I bought an eBay carb someone on this forum recommended. I don't think this had anything to do with carb but the motor sputters and runs for a few seconds. A white/ grey smoke comes through the carb because I have the air cleaner off. As well as the exhaust. Any ideas on that. This motor is killing me
 

Bbqman

Active Member
#6
Well I bought an eBay carb someone on this forum recommended. I don't think this had anything to do with carb but the motor sputters and runs for a few seconds. A white/ grey smoke comes through the carb because I have the air cleaner off. As well as the exhaust. Any ideas on that. This motor is killing me
Totally the wrong carb for an hs40. Nevermind, put the old one back on. Back to trying to fix this one or if anyone knows what did my motor. Hs40 55408c thanks
 

Bbqman

Active Member
#7
the revised # service carb can still be found to replace that particular one with the correctly drilled Idle circuit, mainjet, and passages. its Tecumseh part number 631795a. Tecumseh Service carbs do not come with the choke lever, has 2 holes to position the detent spring (depending on lever used for your application) so you transfer yours onto it and the throttle shaft is made so you can bolt on the correct bellcrank to the top for your application. If it does not come with the bellcrank, simply file off your OG from the shaft and screw it on.

If your looking at a carb that has a pull style throttle lever on it, its for a larger engine application and the circuits and bore will be different, and in the Chinese carb world they are usually too large internally already compared to the OEM's and don't function well.

@ELT Do you need one of the mini bike specific HS 631625 choke levers? I have them in stock, but they are pricey $25 + the ride
I saw that carb it's about $100. I just want this original to work. They are not that difficult.
 

mustangfrank

Well-Known Member
#8
I saw that carb it's about $100. I just want this original to work. They are not that difficult.
I found the genuine carb for 65-70 bucks shipped on eBay and Amazon. Otherwise start over and check every one of those passages with a wire/tool. Don't rely on the "dip", it cleans up surface buildup great but it never clears stuck stuff in jets and fine passages for me.
 

Bbqman

Active Member
#9
I found the genuine carb for 65-70 bucks shipped on eBay and Amazon. Otherwise start over and check every one of those passages with a wire/tool. Don't rely on the "dip", it cleans up surface buildup great but it never clears stuck stuff in jets and fine passages for me.
I have had that carb apart 5 or 6 times. I have torch tip cleaners I used. Even popped out the Welch plugs and cleaned those. Nothing plugged or dirty. No unfiltered gas has gone through the carb since the first time I took it apart
 

mustangfrank

Well-Known Member
#10
I have had that carb apart 5 or 6 times. I have torch tip cleaners I used. Even popped out the Welch plugs and cleaned those. Nothing plugged or dirty. No unfiltered gas has gone through the carb since the first time I took it apart
Oh I've been following you on this, I feel your pain. I'm not sure what type of torch tip cleaner you're using but I swear by those 5 buck carb wire tools. I used strands of wire brushes for years when I just had my cycle and it was the only thing I owned with a carb.

Not sure where you left off but did you loosen the gov arm, screw or linkages when you took carb off and on? That'll cause erratic idle more so but just brainstorming.
 

Bbqman

Active Member
#11
Oh I've been following you on this, I feel your pain. I'm not sure what type of torch tip cleaner you're using but I swear by those 5 buck carb wire tools. I used strands of wire brushes for years when I just had my cycle and it was the only thing I owned with a carb.

Not sure where you left off but did you loosen the gov arm, screw or linkages when you took carb off and on? That'll cause erratic idle more so but just brainstorming.
No I didn't. I even made sure it was adjusted correctly after I put the carb back on. I am going to take it down to my local lawn mower repair guy and see if he can get anywhere with it. Thanks for your help
 

1971_MB1A

Well-Known Member
#16
No hating, I enjoy originality that's all. Thanks for the comment
Are you totally sure that it is a carb problem ? Did you check for pitted points,gap on points,and or timing etc ? I know the China carbs are not that great but I've really never had too much trouble with them or even with the Tecumseh originals once they are cleaned and or rebuilt etc. I've had/have several engines that have literally sat for decades and I can usually have them up and running very well within just a few hours.
 

Bbqman

Active Member
#17
Are you totally sure that it is a carb problem ? Did you check for pitted points,gap on points,and or timing etc ? I know the China carbs are not that great but I've really never had too much trouble with them or even with the Tecumseh originals once they are cleaned and or rebuilt etc. I've had/have several engines that have literally sat for decades and I can usually have them up and running very well within just a few hours.
Points, condenser, plug are all new. Coil tested good. I did not check the timing. I think that is above my experience level. It looks like the magneto has never been moved. This bike was extremely clean internally even the carb.
 

Bbqman

Active Member
#18
Points, condenser, plug are all new. Coil tested good. I did not check the timing. I think that is above my experience level. It looks like the magneto has never been moved. This bike was extremely clean internally even the carb.
Points were set at .020
 
#20
Mikunis generally come with 30 pilot jet and 100 main....I start with a 15 pilot jet and a 130 main and go from there....nothing is a plug and play....I was 3 days rejetting last week....it’s a process but very well worth it....buy several jetss....12.5, 15, 17.5, and a 20 pilots should be a good start...mains 125 and a 130 to start....and again it depends on the modifications to the motor....if it’s stock you MAY want to start with a 16mm and see how far you want to go....just my opinion....there are several more well versed than me on this subject and I’m sure they can chime in and give you better advice.
 
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