What's wrong with my carburator? (2 Viewers)

[60 40]

The latest issue in my 60/40 Project:

The good news I've started up my 40 for the first time in 21 years!

2F swap with stock carburator and most other swappable items from a running '83 FJ60. Adjusted the valves, aimed the distributer at the #4 cylinder, primed the gas, couple cranks didn't even give it choke or throttle and it fired right up and idled really nice even though I haven't set the the timing yet or adjusted anything on the carb.

Here's the issue, as soon as I tap on the throttle the engine immediately starts to rev up and have to I turn it off at about ~2000 RPM I'm guessing which takes only several seconds. When I restart it without using the gas peddle it once again idles fine at a nice idle speed until I tap the gas. The pedal and all the linkage and cable all seem to be retuning to the idle location after I let off the gas. There are many vacuum hoses and such still disconnected but I can imagine a vacuum leak could lead to sudden acceleration?


I'm thinking it's an internal carburator issue but thanks in advance for any other ideas as well.

What could be causing these symptoms?

 

[Mr. Green]

Gotta be the spelling! Sorry couldn’t help it I will reread.
Linkage or cable? How do you know it’s returning to idle position? I would mark it and recheck with a helper to confirm.

 

[Pighead]

2F swap with stock carburator

Stock for what year? Pics of carb and the limkage? Are you missing a return spring?

 

[devo]

I’m no expert but I’m gonna take this shot at it:
In order for the rpm to get to 2000 there has to be good a good deal of air and fuel being sucked through the carb . Even though you say the linkage returns to the idle position I think that a throttle valve/butterfly is staying open?
Maybe spray the carb down with carb cleaner and try to free up the throttle plates ?

 

[ceylonfj40nut]

Throttle return spring is likely missing or weak is my guess

 

[charliemeyer007]

Do you have a cable throttle? Maybe its frayed some on the inside or gunked up. Use a cable luber with wd40 to wash out rust and crud then use cable lube spray.

https://www.amazon.com/Motorcycle-Lubricator-Motorcycles-Bicycle-Scooter/dp/B0C8GBW271

https://www.amazon.com/PJ1-1-12-Cable-Lube-Aerosol/dp/B00HRXOGVW

Run some good fuel treatment cleaner in your gas. At least use carb to hose out the guts of the carb, way better to actually take it apart and clean it properly.

 

[60 40]

Gotta be the spelling! Sorry couldn’t help it I will reread.
Linkage or cable? How do you know it’s returning to idle position? I would mark it and recheck with a helper to confirm.

Ha, yep spelling has never been my strong point.

Linkage and cable. Brand new stock '69 cable running to a linkage to cable bellcrank from a '76 then linkage to a stock '83 carb from a 60 series.

I dredge up some pictures and get some new one with good lighting. I agree seems like a bad, weak or missing return spring might be the issue I'll double check those at pedal and carb and perhaps add one at the bellcrank....

 

[60 40]

Here's a picture of the bellcrank in place (came a little bent) before restoration and one of it not installed and painted. It looks like there is a place a spring could go, I'll give that a try as well as some carb cleaner to try and free things up.

 

[60 40]

Well there you go added a couple springs and issue resolved!

Guess since I'm running the cable to linkage the linkage needs a way to be pulled back otherwise the mighty 2F just sucks the butterfly valves open.

Thanks for the reality check guys, check the simple stuff first. I'll figure out how to route the spring nicely since it appears to be a critical component and move on to the next challenges.