High idle issue please help

[Miller8808]

I purchased a basic performance kit for my sons buggie I have only put on the header, muffler, air filter/adapter and rejetted the carburetor with a .036 jet and 140 emulsion tube. When I start it on choke it idles at a lower rpm but when I take the choke off the buggie wants to take off like the throttle is open. Can anyone please help with this issue? Attached are photos of the engine. It’s a 196cc unmarked clone engine.

 

[mckutzy]

First..... Jack it up on blocks against a tree/wall ect immovable object... This help incase it walks off the stands and then darts off in a random direction to kill something...
(That is if you can't easily dismount the drive chain)

You can try to lower the rpm via that black idle screw pictured on the carb, when the choke is off... If that doesn't help... I would retrace the throttle cable, back to the engine...

I had a runaway engine on a brand new 208 powerfist motor...
Looked at everything just about to box up and return it, unbolting the throttle cable and found it had pulled the throttle arm a little open when I had tightened the screw... Off handedly I had restarted to check... And it idled fine... Good to go now...


Edit: Another item(s) I see is you might need another return spring on the end of the throttle arm, this helps the return to idle of the throttle when cable connected.
I would also back out the throttle stop screw as far as it can go without popping off,
Not allowing the motor to rev fully will potentially do more harm the belt.

 

[Miller8808]

Thank you sir, I will try this and then go from there. It will be a few days before I can, this is a Christmas gift for my son and he’s is now on the way home from his friends house. I have to hide it in my shed until I get a chance to work on it.

 

[carbidecutter]

Something is causing your governor to open the throttle. I'd do as Mckutzy suggested. Another thing you can do is jack it up, remove your throttle cable and test with the hand throttle. That should tell you pretty fast if it's a throttle cable issue.

 

[Joe-405]

I can tell you by looking at the pics your throttle is WIDE open. So your linkage or something is wrong.

 

[Miller8808]

Thank you guys your help is very much appreciated.

 

[mckutzy]

Ahhh... Loosen the throttle plate nut on top a shade... Till its free playing.

 

[Miller8808]

Ok guys I got some time to mess with it. I took the throttle cable off and it did nothing. I backed the idle screw out and it did nothing. I think it may be a problem with the governor, I can hold it in a certain spot and it does fine but when I let it go it’s like it’s wide open. How would I fix this?

Edit: the throttle lever does nothing regardless of where I hold it. It stays wide open. It seems like the governor is holding the throttle wide open, is that possible?

 

[Clifton]

The governor, in addition to limiting top speed, holds the throttle open to maintain a certain rpm at idle despite the load on the engine. In addition to this, when the engine is not running the throttle is held open so that it starts easier. This is normal.

The fact that it idles fine with choke but races off without it means that it's not getting enough fuel at idle.

Under the plastic idle speed adjustment screw there is a plastic jet with a tiny brass insert and an even smaller (0.016) hole. This controls the amount of fuel at idle and low speed of the engine. I would make sure this jet and the area it goes into is clean by spraying it out with carb cleaner, making sure the tiny hole isn't clogged. Could spray out whole carb while you are at it just in case.

A lot of people have no problems running the stock idle jet size after upgrading air filter etc.. but if nothing else works you could try enlarging the hole slightly with some tiny drill bits maybe a 0.017 or 0.018. You can also buy the idle jets from some places such as arc racing or ombwarehouse but I had to sand mine slightly to get it to fit as the ruixing carburetor idle jet they sell was slightly larger than the carb the predator had.

 

[Joe-405]

If I’m not mistaken he said he can hold the linkage closed by hand and it idles just fine.

 

[bob58o]

Check the linkage (spring?) from the throttle lever to the governor arm.
If the linkage from the gov arm to the carb is correct (I assume it is) and the throttle level doesn't move the butterfly, then you've lost the linkage connecting the throttle lever and the governor arm.

There should be a spring that pulls the governor arm towards the carb when you pull the throttle lever towards the carb, IIRC.

I haven't used one of those carbs in while.


Don't blame me for the quality of the pic. It's a screenshot from a Tube vid (if you couldn't already tell).

If you need one, I'm I MIGHT be able to find one. I should have one in my kitchen somewhere from my last build. I'll ship you it if you need one and I can find it.

 

[bob58o]

Do you have your Tear-Down Pictures?
If you took detailed photos during the tear down process, it makes it easier so see what is different when it goes back together.

Tear down Pics. Before, During, After, ... Step by Step are VERY helpful. Even after taking an engine apart and putting it back together a dozen times or so.

EDIT: The spring wasn't in the box I hoped it was going to be in. The chances of me finding it are pretty small now. I should stop offering to ship parts til I know where they are.

 

[carbidecutter]

There should be a spring that runs from the throttle lever to the governor. It sounds like you're missing that spring. I'm not talking about the one that rides on the governor rod but one that ties directly to the throttle lever. I have a Lifan and don't know if it'll help but I'll post a pic anyhow a bit later.

I think Bob58o nailed it. The larger spring in the pic he posted is most likely your problem. You might look under the gas tank. It could be laying there unhooked.

 

[Miller8808]

Thank you everyone I will try everything Friday. I may be back then with more questions lol.

 

[bob58o]

Thank you everyone I will try everything Friday. I may be back then with more questions lol.

Friday? But today is Monday.

 

[mckutzy]

If that's what you need... Try asking a lawnmower shop or rental place... They'll for sure have a small bits box for stuff like that...
Bring a sixpack to see if that'll grease there motivation.

Sadly if you were in Canada I'd be able to send you that easilly enough... Sending across is a bit more difficult.

 

[Miller8808]

Friday? But today is Monday.

Yes it’s a Christmas gift for my son. I’m off Friday and he will be in school I have it hidden in the shed right now.

 

[Miller8808]

Alright, I had time today to check out the buggie and I found the problem!! The spring that goes from the throttle to the governor arm was behind the flywheel cover mount. I took it off and put it in front and now it idles and runs great!! I guess qc missed that one. Thank you to everyone for your suggestions and help.

 

[mckutzy]

That'll do it.. Good to hear about success of it..