Throttle help

[Russchastain]

Howdy all! I just got a little mini bike with a Briggs engine. Supposedly it’s an old frame that was sold through a catalog in 1969, blah blah... whatever. I have no way of knowing its age.

I finally got the newer Briggs engine running smoothly, but the throttle hookup is primitive and VERY sensitive... just a little goose to the throttle and the bike is out from under ya. The cable from the twist throttle is attached directly to the governor arm and pulls directly on the link to the carb throttle shaft. Seems like there should be some sort of linkage to make it less sensitive so I have some room between “slow” and “wipeout.”

I’d appreciate any input and suggestions. Thanks!

 

[madprofessor]

You're pulling on the wrong thing. The governor arm (when employed as per OEM) barely has to move at all to overcome the throttle you supposedly are applying to the carburetor. The throttle cable should be pulling on the carburetor linkage itself, which isn't nearly so tiny a motion.
Your throttle cable should be hooked up there instead of to the governor arm.
Look up in the search at the upper right of the page about throttle hookup, or same on YouTube, you'll see what I mean.
Remember that the further out on a motion arm you connect to, the less sensitive it'll be.

 

[Russchastain]

Thanks. The rod visible in the photo IS the carb linkage. As you can see, the cable and rod attach to the governor arm in almost the same spot. So it’s almost as if the cable is pulling directly on the carb butterfly.

I’ve done a lot of searching, but I’ll try some more. Appreciate the input.

 

[Functional Artist]

It does look like the throttle cable, is pulling on the wrong thing
...so, please post a pic of your carburetor (& linkage)

 

[Russchastain]

Here is a pic showing the rod between governor arm and carb throttle shaft, another pic of how the cable is connected to the governor arm on my machine, and a pic I just found of someone else’s engine to show the OEM configuration for this engine. I don’t have any of the missing parts and don’t really want to buy anything for this machine, so I’m hoping to fab something.

 

[Functional Artist]

I may be wrong
...but, the way that it's configured now, (I think) your (maybe) prematurely advancing the timing, everytime you accelerate.

or
What is your gear ratio?
...maybe you have a "rocket" on your hands

 

[Russchastain]

I don’t know the gear ratio, but it feels like a rocket when it gets goosed. I had to rig a foot rest on the front fork to help distribute my weight so I don’t flip.

 

[Functional Artist]

Does it run good & accelerate good, the way it is set up now?
...just want's ta take off on ya?

What is your top speed? (estimated)
...it puts along?
...it's kinda quick?
...or fast enough for me?

 

[Russchastain]

Does it run good & accelerate good, the way it is set up now?
...just want's ta take off on ya?

What is your top speed? (estimated)
...it puts along?
...it's kinda quick?
...or fast enough for me?

I just made a change...

As stated, there was almost no throttle movement between “barely moving” and “crash.” So it was really hard to ride it at all. Top speed I have no idea because I don’t think I can stay on it that fast! But one little tiny twist of the throttle and the bike would shoot out from under ya.

I extended the governor arm and got about 30% more movement between idle to WOT, so it should be a little more controllable now. Just need the rain to quit so I can take a test ride.

 

[madprofessor]

In the pic of the different (red) machine with OEM parts hookup, note that there's no cable pulling directly on the governor arm. Motion back/forth of the throttle should be pulling directly on the carb connection itself, but any attachment to the governor arm should only be by springs and/or that sliding linkage setup in the pic, however that works. Predators use simple springs and rods. If the governor arm starts to move via the governor in the crankcase, it would be in the direction of pushing the carb connection closed.

 

[madprofessor]

Check out this YouTube link at about the 3 1/2 min. mark, you'll see the guy moving the throttle like a minibike throttle cable should be hooked up somewhere to do. You can see with his explanation how the governor arm is not affected/pulled by whatever you're doing with the throttle, that the arm moves by itself from the governor internals, and when it does it's supposed to overpower the throttle to reduce the gas getting into the carb, therefore slowing down the rpm's.
Governor adjustment Briggs & Stratton small engine - YouTube

 

[Russchastain]

Thanks, I watched that yesterday.

 

[pearl111]

I would also change the sprocket on the back wheel to a 60 tooth or a little less around a 54 tooth.

 

[Russchastain]

I would also change the sprocket on the back wheel to a 60 tooth or a little less around a 54 tooth.

What tooth count do you think I have now?

I made another change to the throttle setup and it’s much better now. Will still haul butt, but now it’s controllable so the bike doesn’t try to shoot out from under. I can’t upload a video, but here are a couple pics of it in action.

 

[pearl111]

What tooth count do you think I have now?

I made another change to the throttle setup and it’s much better now. Will still haul butt, but now it’s controllable so the bike doesn’t try to shoot out from under. I can’t upload a video, but here are a couple pics of it in action.

I tried counting I think I counted About a 72, tooth count. I'm sure if it were around 54/60 It would not take off so fast.
I had a 72 count on doddle bug mini bike but it also kept trying to flip me off the back. So I put a 60 tooth sprocket on the back wheel,
and that worked out great for me.

 

[Russchastain]

I tried counting I think I counted About a 72, tooth count. I'm sure if it were around 54/60 It would not take off so fast.
I had a 72 count on doddle bug mini bike but it also kept trying to flip me off the back. So I put a 60 tooth sprocket on the back wheel,
and that worked out great for me.

Thanks for the input. It seems like it would work the opposite way? Anyhow, it‘s manageable now, but the brake sucks.

 

[madprofessor]

Pictures just "wrenched" my brain. I'm out.

 

[ezcome-ezgo]

What's the purpose of the die?

 

[Russchastain]

What's the purpose of the die?

It’s acting as a nut to hold the bell crank in place. I needed a fine thread 1/4” nut and didn’t have one, but I did have an old Chinese die.

 

[madprofessor]

What's the purpose of the die?

Now I'm wondering that too. Thought it couldn't be anything but a substitute for a nut to hold the lever, but now?