Tec HM-40 running problems

kawtoy

kawtoy

New Member
#1
#1
I just picked up this mini a few days ago. I think it is a Bird but can't say for sure. The plate on the engine says HM 40 so I assume it is a Tec 4hp. I got it running and it will do a burn out in the garage... as long as I am no on it. With me on it the dang thing won't even move. If I push myself some it will hold steady at 2mph, barley enough to stay upright. I checked compression and it was 70psi, both with throttle open and closed. Not sure what these old engine should have for compression. I also have no idea how to set the carb up. I can work on KZ1000's all day long but this little engine and carb have got me stumped. What should I adjust or check first? What is the correct spark plug and plug gap? I am 6'1 and 200lbs. This should be able to move me along at a decent speed right? I just want it to cruise on, not trying to race anyone. Thanks


 
J

jimh

#2
#2
Probably should have 100+ compression with throttle open. Turn the screw in on the bottom of the float bowl all the in and back it out about 1 1/4 turns. clutch may be slipping too.
 
kawtoy

kawtoy

New Member
#4
#4
It idles ok, maybe a little high, and it revs fine. Smokes a bit. Might be from bad rings or might just be from sitting so long. The low compression leads me to say bad rings or valves. I will be tearing it down for a rebuild this winter but I was hoping to get some use out of it first so I can see what improvements and mods need to be done.
 
kawtoy

kawtoy

New Member
#5
#5
How should the choke be hooked up on this engine? Right now it has a spring that keeps it open. When at full throttle there is a piece from the throttle linkage that pushes the choke closed a little.
 
delray

delray

Well-Known Member
#6
#6
hey kawtoy,that is a 5hp? or 6hp style block. 4hp blocks dont have the oil filler tube mount on top of the side case and also dont have the steel mounting plate on the bottom of the engine and also dont have that type of carb set-up. 4hp have a intake and carb and i think 5hp also? i have this same bike but all original. the original set-up is a 4hp tecumseh with a slat intake and a torque converter.
could still be a 4hp that tecumseh use a 6hp type block ,but kept a small bore or stroke. making it only 4hp. looks to be a old snowblower engine?
that fiberglass body on top of the frame is very rare. i have only seen couple of them pop up on the internet,but no info on it?
:scooter:.......................:thumbsup:
 
joshhoward

joshhoward

New Member
#7
#7
Hey Delray & kawtoy

Its a H40 ive only seen a few of these. Its a 4hp H block. With the bracket mounted on the carb like that, and the breather tube that gos to the air filter it was probibly mounted on a tiller or some other summer type tool. After you get it running it should be nice and torquey for a 4hp.

Hey Kawtoy im going to send you a PM just give me a call and ill walk you through the carb adjustments.


Josh


Josh
 
delray

delray

Well-Known Member
#8
#8
josh,is that a 6hp block? with a small bore or stroke. for example can that side cover bolt up to a reg-6hp block and not bolt up to a reg hs-40 block
:scooter:......................brian
 
joshhoward

joshhoward

New Member
#9
#9
Hey Brian

Yes its the same as style as the H50, H60, and H70. But im not sure what parts are interchangeable. It almost looks like the HH block whitch is cast iron. Still cool a BIG BLOCK 4HP.


Josh
 
kawtoy

kawtoy

New Member
#13
#13
So I got the mini running a little better but still not good. I think it has some issues. I got a new clutch for it which helped a little but it still very weak. I have to push to get going but once going I got up to around 15mph, certainly not setting any land speed records. One issue, and the main one I think, is a pretty bad exhaust leak at the head. The exhaust coming from under the head is pretty stong and I assume that is where my low compression is coming from. It also smoke pretty bad when under a load so the rings will need to be replaced. I am going to Mid-Ohio this weekend for the Vintage Motorcycle days so I would really like to be able to ride the bike around there. Any advice to help squeeze a little more life from the old girl? I have the bottom jet set 2.5 turns out. What should the side screw be set at? There is no filter on it now. Will it make much of a difference in how it runs? Should I run straight unleaded or should I add some lead additive? Any suggestions would be great
 
jesse8931

jesse8931

New Member
#14
#14
the bottom should be around 1 1/2 and the side the same you can mess with them a lil but if that doesnt help you have problems else were i had a problem with not having any balls i messed with the jets clocked at 52mph
 
RuppParts

RuppParts

New Member
#15
#15
KAW, with engine smoking, dont worry about lead adddtives.
The smoking could be from diluted engine oil or overful, when was it changed last?
If the head gasket is leaking, that is a DEFINITE power loss problem. Shoot me a pm if you need a head gasket at mid Ohio

Use an air filter, the Tecumseh air filters work great and do not hamper any perfromance on stock and slightly modified engines

Seeing your pics, your engine ID tag is in place.....shoot me the #s off of it if you want engine info
 
delray

delray

Well-Known Member
#16
#16
hey kawtoy,i see other big problem that you are having. with the engine running very weak and only putting out maybe 2 or so hp and also using a clutch set-up and a small rear sprocket with that tall tire and the weight of adult on it? that will be just about how it will perform. the first thing try doing is rebuild motor,if can. then see how it will perform. you also got to remember that the bike original use a torque converter with a small block 4hp tecumseh. with the torque converter it could pull the bike from a died stop with that small rear sprocket. so if you dont have the $$$ to puchase a tav-2 you still may have to use a jackshaft and the only kind you can use would be a bolt on . with that type of frame it would be to much work to use a weld-on with the lower rear swing arms.:hack::hammer::weld::grind: :doah:
my bike still has the original sprocket with the built in drum and you can't change the sprocket really with anything bigger? so your kind of stuck with a bolt on jackshaft or a tav-2 if you want it to perform good from a died stop.
just maybe with that motor rebuilt and being a big block 4hp. i would think it might put out enough torque to pull you from a died stop? weight of a adult(you) could still be problem?
keep us posted kawtoy, your's is only the second bike with the fiberglass body i have seen in last three years. i think could be very rare to find.

http://new.photos.yahoo.com/brian_c_53711/album/576460762334530203/photo/294928803494935548/0

:scooter:..................................:thumbsup:
 
Last edited:
R

ralphy

New Member
#17
#17
I have a rupp roadster with a 4hp Tecumseh engine. I am 6'3' and I weigh about 300 lbs, and my bike will do 30 mph with me on it, so it definitely sounds like there is something wrong
 
kawtoy

kawtoy

New Member
#19
#19
RuppParts said:
KAW, with engine smoking, dont worry about lead adddtives.
The smoking could be from diluted engine oil or overful, when was it changed last?
If the head gasket is leaking, that is a DEFINITE power loss problem. Shoot me a pm if you need a head gasket at mid Ohio

Use an air filter, the Tecumseh air filters work great and do not hamper any perfromance on stock and slightly modified engines

Seeing your pics, your engine ID tag is in place.....shoot me the #s off of it if you want engine info
Click to expand...
Thanks. I sent you a PM. I will get you some numbers when I get home. If you could bring a head gasket with you I can replace it while at Mid-Ohio and see if it helps any. If not I will buy something else there to ride around on and then tear into the Tec when I get home. My vendors booth is #5, or around there. It is along the fence right near where they rent the gold carts. Stop by and say hello. Maybe someone can get it running better than I can
 
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