HSSK40 Carb recomendation please...

longlongtimeago

longlongtimeago

Member
#1
#1
HSSK40 Carb recommendation please...

Putting together a 1970 Rupp Scrambler from boxes of parts. Lot's of stuff is long gone...

I have a HSSK40 Tecumseh . It was given to me, told it was off a snowblower.

I started it today and was please on how it ran. I guess I need to change stuff to make it work with a throttle cable...no clue on what to do as I have nothing to use a reference.


I've read here you can use a cheapo import carb [off ebay?] Still no idea what I need, or what will work...I found this one...and suggestions?


ebay carb here


BTW I was just going to cut the reverse output shaft off ...that ok to do?



Thanks Jim
 
longlongtimeago

longlongtimeago

Member
#3
#3
Thanks cfh Lots of great info there...

Second question, before I order the part...

My bike is missing the driver portion of the torque converter. If I remember correctly, some are suggesting a comet 20 driver as a replacement, using the original Rupp driven unit. {or a cheapo knock off] If that is the case what modifications do I need to make and what should I use for a belt. If that is NOT the best way to go, suggestions please. Again thanks
 

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cfh

Well-Known Member
#4
#4
A comet 20 driven (available in china version on ebay for about $25) will work. you just need to note the belt size. i believe the ebay ones use a 3/4" belt. and your stock driven will use a 5/8" belt. Not to worry though, it's easy to convert the comet 20 driven to 5/8" belt. you just need to take 1/16" off (using a grinder, etc) the sheave closest to the engine (the one with the brass sleeve.) that's the torque converter part which slides on the engine first. then you can use the stock rupp belt. cfh

Just looked at your snow blower motor. with some work that could be nice. get a new pull start handle (ebay). remove pull starter and rotate it counter clockwise 30 degrees. take off the gas tank bracket. you will need a slant intake manifold for your new carb. And get a new air cleaner (snow blowers have none.) you'll also need a new throttle mechanism (available from OldMiniBikes warehouse.)
 
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cfh

Well-Known Member
#6
#6
Here's stuff you'll need.... i am assuming you have a 1970 roadster or scrambler. cfh

Comet (china clone) series 20 driver 3/4" bore. Must be 20 series! (ebay)
Comet 200421a torque converter belt. https://www.OldMiniBikes.com/comet-tc88-belt-883-80-cog-symmetrical.html
air cleaner assembly 730127. https://www.OldMiniBikes.com/tecumseh-oem-air-cleaner-assembly.html
air filter 30727. https://www.OldMiniBikes.com/tecumseh-oem-air-filter-hs40-hs50-and-others.html
mini bike throttle assembly 730136a. https://www.OldMiniBikes.com/mini-bike-throttle-control.html
pull start handle 590387. https://www.OldMiniBikes.com/starter-handle-tecumseh-590387.html
slant intake manifold. http://blackwidowmotorsports.net/_33301t_slanted_intake_manifold.html
Tecumseh carb 632230 / 632272 (any ebay item.) Note it needs a couple small mods to work well.
 
joshua. c.

joshua. c.

Well-Known Member
#8
#8
longlongtimeago said:
Perfect! I will get it all coming...one question...why am I changing the intake manifold?
Click to expand...
the carb wont sit flat in that frame without a slanted intake. it can be adjusted to work at that angle but its not ideal. also that engine already has a carb and they are a breeze to service so why replace it?
 
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cfh

Well-Known Member
#9
#9
The 1970 model rupps, pre-slanted intake and with 20 degree motor mount, used a diaphragm carb. Diaphragm carbs don't care what angle they sit. But a float bowl carb does care. Hence the 20 degree angle intake manifold used on a slant motor mount and a float bowl carb. Like Joshua said, a float bowl carb can work at 20 degrees, but it would be better to have the correct intake manifold (as used on 1971-1975 rupps with angled motor mounts) so the carb sits level.
 
longlongtimeago

longlongtimeago

Member
#10
#10
Well that explains that... I kinda knew all that but I DIDN'T know the reason for the diaphragm carb was the fuel bowl angle was an issue on the angled engine. Guessing you can't get diaphragm repop carbs huh?
 
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cfh

Well-Known Member
#11
#11
i have not seen any re-issue diaphram carbs on ebay (or elsewhere.) a lot of guys rebuild their originals. personally i like to have my carbs "all the same" (i have many bikes). so i go with the angle intake manifold and use the bowl carb reissue (or a slide 16mm or 18mm or 19mm carb.) but that's just how i roll.
 
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Havasu Dave

Moderator
#13
#13
longlongtimeago said:
8 bucks for a new carb to my door. Rebuild kit costs more than that...
Click to expand...
Those carbs work okay for the casual rider initially, but soon succumb to failure of the inlet needle against the float seat. The original seats were made of a special rubber Tecumseh called "Viton." For some reason, the rubber seats supplied in those cheap carburetors fail fairly quickly, and you'll see fuel pooling and dripping. Make sure you install a shut off valve.

When buying carburetor rebuild kits, I assume they contain the same crappy rubber, but they seem to hold up much better when installed in Tecumseh carburetors, than the cheap carburetors do.

Some of us have experienced casting issues with those cheap carburetors as well. The methanol in the gasoline is going to have a detrimental effect on every orifice in that carb. Using alky-free gasoline will help. When you get the carb, remove the float bowl and check the float level, and ensure the float axle is free.

I know I might be an odd ball, but if I had a bike running fine, that was an odd ball, using a snow blower engine, I'd leave the carb alone. Sure, if you descend some steep hills you might fuel starve it. But do you really want to put a $7 carburetor on a $40 intake manifold, when you have a running engine sitting in front of you?
 
joshua. c.

joshua. c.

Well-Known Member
#14
#14
longlongtimeago said:
8 bucks for a new carb to my door. Rebuild kit costs more than that...
Click to expand...
that is remarkably cheep. I do have some advice to help this engine run without as many maintenance issues in the future. its a good idea to run stable in the fuel to keep it from gumming things up and have an in line fuel filter to catch anything that has gotten into the tank and a fuel cut off valve to shut the fuel off when done and with this engine you can prevent spark problems for several years just by painting both the coil and magnet.
 
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cfh

Well-Known Member
#15
#15
I agree that using a fuel shutoff is a good idea. personally i run pump gas. but it does have negative effects on new carbs (it seems all new carbs are china made.) i run the gas out of the motor too. when i'm getting ready to stop for the day, turn off the petcock, and run for a minute until it dies. obviously i don't do this if i'm riding in a few days. but i think it is a good idea. i've noticed pump gas swells carb rubber gaskets, so shutting it off makes sense.

on the float seat rubber issue, this has happened to me a couple times (leaking carb). i've bought probably 20 or 30 of these cheap $8 carbs, and yes it has happened. but for $8, i'm willing to put up with it. in my experience it doesn't happen a lot, but yes, it can happen.
 
longlongtimeago

longlongtimeago

Member
#16
#16
The $8 [actually $7.24] dollar eBay carb showed up this morning... looks good to me. I expect my BlackWidow order soon, TC shows any day...Still on the hunt for a intake. I'll get it all together and ridable then take it apart and de-rust and paint it...
 

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