Throttle setup on a 2-stroke Tecumseh HSK845

Arwing64

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I removed a 4.5 HP Tecumseh 2-stroke HSK845 engine from an MTD snowblower and wanted to use it for a mini bike project.
I am well aware that the motor mounts for those engines are off to the side and have already had that figured out.
The carburetors on these engines is very similar to most horizontal shaft Tecumseh engines.

These engines do not come with any sort of manual throttle and the throttle is only controlled by the governor. I was wondering if there is a way to make a manual throttle setup on these engines. My plan was to hook the throttle cable for the mini bike to the engine but also use the governor to act as a rev limiter. I really didn't want to risk running without the governor so I don't blow it up. It will also need some sort of throttle return spring to bring it back to idle.

I know I need to have a throttle lever like what is on any other engine for this to work, but how I would attach it to the carburetor and the governor is the real question. I am not sure how to go about doing this. Any ideas?
 

Russ2251

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Running without the governor should not be an issue... unless you are in the habit of free revving the engine.
Free revving means something like running it wide open without a load.

Your automobile has no governor. You wouldn't free rev your automobile engine would you?
It would not last very long if you did.
I've been running ungoverned Lawn-Boy engines on a '68 Fox Doodle Bug and 2 gokarts since 2007. Of the gokarts one is running a single, the other twins.
All will go over 50 mph.
 
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Arwing64

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Running without the governor should not be an issue... unless you are in the the habit of free revving the engine.
Free revving means something like running it wide open without a load.

Your automobile has no governor. You wouldn't free rev your automobile engine would you?
It would not last very long if you did.
I've been running ungoverned Lawn-Boy engines on a '68 Fox Doodle Bug and 2 gokarts since 2007. Of the gokarts one is running a single, the other twins.
All will go over 50 mph.

Dude! That is insane! I've never heard of anyone using Lawn-boy engines for anything (other than lawn mowers of course). Pretty cool!

But I get what you mean about not using a governor. The thing is how fast can these engines go without blowing themselves up? Like, what would you say is the maximum safe RPM (for a stock motor)? The engine is a 4.5 HP Tecumseh 2-stroke HSK845 139cc.
 

Russ2251

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how fast can these engines go without blowing themselves up?
Unknown to me, but Lawn-Boy Duraforce engines are designed to run at 2900 ± 300 rpm.
I run them at ~6500 to 6700 rpm (under load) with no problems.
To be very honest with you...I do not trust Tecumseh 2 cycle power plants at all.
 

Arwing64

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I know what you mean by Tecumseh. I don't trust them either, but the only reason why I am using the Tecumseh engine is because it was available to me. Plus there seems to be more of them just laying around in other snow blowers. I couldn't find any Suzuki or R-Tek engines from any snowblowers except for the ones I already have on working snowblowers.
But would you think it would be safe at around 4500 rpm at least? I could possibly see if I could get a billet connecting rod or something. I don't know much about the 2-stroke Tecumsehs.
 

Russ2251

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But would you think it would be safe at around 4500 rpm at least?
I really do not know.
Experiment with it. Put a minimum of effort into it and just take from there.
As I mentioned before...DO NOT FREE REV IT!!! If you do, harmonics will set themselves up and destroy the internals... I guarantee it.
 

jp1961

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Check YouTube for lots of DIY go cart/mini bike projects

Regards

Jeff
 

Russ2251

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Resultant carnage of free revving a Tecumseh (or any) 2 cycle:
dead tecumseh 2 cycle.jpg
 
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