Hs40

#1
I bought an old Fox mini, and it came with an Hs40, and (what I think is) an old HS35 or HS40. I haven't found any numbers yet. The 35 has a lighting coil, but no flywheel and no compression. The HS40 is good (I think). The carb is pretty nasty. I was thinking of rebuilding it, but $20 for a new carb is pretty tempting. I've got an new carb off of a 212 pred. Can I make that work if I whip up an adapter? Will that be too much carb? I'm not going for a restore. I just want it to run. Any input is welcomed. I'm also not afraid to rebuild if you think the old carb is worth it. Im pretty excited to start this.
 
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#3
If you aren't worried about restoring it, I would put the $20 aftermarket carb on it. The time you save from the rebuild is worth it alone. Get me some engine numbers and I'll give you the part number.
 
#5
I wouldn't use that one with that choke lever...^

Again, send me some engine info and I'll get you the proper number or I can guess if you want?
 
#7
Mini bikin', do you know what the bore of an HS35 is/was? I've got another parts motor that I just opened up to what carnage was hidden. It was about 2.625ish. Is that a 35 or a 40? Just curious. I may tackle both of them. The bore did show some scoring. How do I know when to hone it, when to bore it, and when the block is toast?
 
#8
Mini bikin', do you know what the bore of an HS35 is/was? I've got another parts motor that I just opened up to what carnage was hidden. It was about 2.625ish. Is that a 35 or a 40? Just curious. I may tackle both of them. The bore did show some scoring. How do I know when to hone it, when to bore it, and when the block is toast?
Looking at the back of the engine, is the exhaust on the left side or right side?


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#9
Looking at the back of the engine, is the exhaust on the left side or right side?


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It's on the right. It has the flange on it. I got this with an old 67 Fox (that's what the guy said it was) Trail Tramp. I have an exhaust that may have been original. It fits over the flange that is screwed into the exhaust. I can't find numbers anywhere. I did find a few websites that said the 3.5hp and 4.0hp had the same bore size of 2.5". I also found this site Tecumseh | Classic Engines that listed several engines with a 2 5/8 bore. It does have a lighting coil, but I don't have a flywheel with it.
 
#10
Exhaust on the right side of a small block is a HS40 or HS50. Exhaust in the left side is H35 and down.


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#12
David,
According to the Tecumseh manual, H35 and H40 were both 2.5
All HS 40's were 2.6
Thanks, Dave! I bet this is 2.6. I'm not using digital calipers. I've got some cheap calipers from HF that I use. I don't normally do this kind of work. I'm pretty sure this is an HS40. I am now on the lookout for a cheap flywheel for it. I would love to do the lighting coil with it, but I may have to just go for a standard flywheel for now. I don't want to dump a ton of money into this little motor. I'm partial to clones (only because I feel like I know them way better), and I can get one of those for $100. I don't want to dump $200 into an old motor that I may never figure out. I'm going to have a blast rebuilding this thing.

By the way, you still got that Fox/Rupp exhaust for sale in the classifieds? I may be giving you a call. I've got one for the Fox that is pretty rusty, and yours sure is purty.
 
#13
Okay, I think the complete HS40 is ready. It will be test fired when I get the new carb. I've got the beat up HS40 totally disassembled. I'm now focusing on it. It's all there except for the flywheel. It'll need some gaskets and an oil seal for the crank. One of the lifters was a little crusty on the top. I've found some lifters (part number 27241) for cheap, and it looks like they might be used on the HS40, HS50, and HS60. I was wondering if the lifters out of a Briggs 5hp might fit? I think I have a set somewhere, and if they'll work, I'll dig them up. Anybody ever swap those parts out? Also, I'm still thinking about the flex hone. If I do that, will I need oversized rings? I just want to clean up the bore, not really bore it bigger. Never honed anything, and I thought this would be a great block to practice and learn.
 
#14
Well, the Briggs lifters fit in the block, but they're a little bit taller. I'd say 1/8" at least. I think that might be too much. Maybe cause a little coil bind? I think I'll spend the $5.00 on a new set of Tec lifters.
 
#15
And do I need part no. 34854 for my ring set? I'm gonna borrow my neighbor's flex hone today. We'll see where this thing leads! I'm taking pics, so I'll post them all up. I may even make a new thread that shows what I'm doing. That way you guys can all laugh and tell me what I'm doing wrong!
 
#17
Well, my HS40 is pretty beat up. There are gouges in the wall of the cylinder that I can actually stick my thumbnail in. I am sure it could be bored, but it's too deep to hone. I had a three inch, three stone hone, so it would have been a waste. I also found a small crack in the bottom of the block under tons of sludge. I'm sure it could be sealed with JB Weld, but the cylinder walls were enough to discourage me from moving forward. It was just an extra block, so I don't want to dump too much into it now. I'll give it to my brother-in-law to bore at his shop. I just need to find a piston that will fit and work with my rod.

As for the other HS40, I got the carb in the mail yesterday. I have a small muffler, but it won't fit without a header pipe. I may see what I can find today. I really wanna see how this thing runs. The piston and cylinder walls were really clean. I haven't opened up the side cover yet, but that will happen today. I want to clean it out and get some new oil in it. I'll post up my progress when I find out more.
 
#18
Well, my HS40 is pretty beat up. There are gouges in the wall of the cylinder that I can actually stick my thumbnail in. I am sure it could be bored, but it's too deep to hone. I had a three inch, three stone hone, so it would have been a waste. I also found a small crack in the bottom of the block under tons of sludge. I'm sure it could be sealed with JB Weld, but the cylinder walls were enough to discourage me from moving forward. It was just an extra block, so I don't want to dump too much into it now. I'll give it to my brother-in-law to bore at his shop. I just need to find a piston that will fit and work with my rod.

As for the other HS40, I got the carb in the mail yesterday. I have a small muffler, but it won't fit without a header pipe. I may see what I can find today. I really wanna see how this thing runs. The piston and cylinder walls were really clean. I haven't opened up the side cover yet, but that will happen today. I want to clean it out and get some new oil in it. I'll post up my progress when I find out more.
The HS50 had several bore sizes over the years, if you get one of the smaller bore size pistons you could use it as an over sized piston for your HS40. You can actually bore out pretty big with the HS40 but, the the bolt hole for the shroud has to be welded up/brazed before boring, so there isn't a hole in the cylinder wall when done.
 

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