So, I was the lucky recipient of a '89 518H - a shade under 500 hours on it.

Late last season, the throttle started bouncing uncontrollably. I had the carb professionally serviced, and it ran fine for about 3 hours (which unfortunately spanned the winter, so going back to same service place is probably not going to work)

Symptoms:

- Bouncing throttle (usually starts after about 10-20 min runtime)
- Will stall when I engage pully quickly, usually need to gingerly engage it
- Can *occasionally* get it to run somewhat normally with a quick choke hit, although not always, and never for long.

I'm giving it a good 30ish min soak with MMO straight down the carb for now - maybe even longer

Otherwise - the tractor is in fabulous shape - it's been garage-kept most of its life, and has never left my family.

Please help me from donating it to some lucky person who is better with engines!

i look at the govener spring tenstion . you can look up the procedure on how to adjust it properly on toro.com u need ur tractor model an u can d/l the manuel an print it out but loook under carb an linkage adjusments cuz it could also be the rod that goes grom the govener to the carb that could be bent, out of adjustment,ect hope this helps an sorry i can not link you to toro.com

I'm guessing you have some dirt in the fuel system. If you don't already have one install an inline fuel filter in the fuel line between the tank and fuel pump.
It would be best to pull the carb and clean it, but you may get lucky and be able to disolve the dirt with some good cleaner. I like seafoam carb cleaner, it's good stuff. I buy it at my local napa. TSC also sells some good stuff, it's called Chem-Tool, it works almost as well as Seafoam.

Couple of notes:

1) inline fuel filter was present before/after service - was replaced as part of carb repair.

2) Looking at page 7-6 in the onan manual - going to look at the governor spring.


Wish me luck!

When you winterized it did you run it out of gas? You can try to clean the carb a little without taking it apart. Close the gas petcock, and run it completely out of gas. On the bottom front of the cab there is a plug. Remove that plug (a little gas may come out) spray inside with gumout especially where the jet is. You will be able to see the jet through the hole.

If you do donate it, I sure hope you're near me

Welcome to RedSquare

I'm about 30 min from you in Monroe, CT (uh oh - I'd better fix this! )


Going to let the engine cool down a bit, and try this, too. Thanks all!

Another thought....whats the inside of your fuel tank look like?
If there is any crud/sediment in it it could be causeing a clog at the inlet screen?
There's a small screen in the tank just inside above the fuel shutoff petcock.
Hope you get it figured out, but does sound like a fuel delivery problem.

I had the same problem with a 520H...turns out the idle jet was pluged up and it was running on the main jet. All it took was removing the idle mixture screw...spraying carb cleaner in the hole and the air passage port in the throat of the carb ..runs fine now. One more thought is the fuel line...if it's the origanal line ,it could be rotten on the inside hece the gas is picking up tinny pieces of fuel line which replugs anything you clean. the first thing that I replace on a tractor I buy to get running is the fuel line...has saved me alot of problems....

Hmmm - did notice something wheick I find odd. Where is the line that ends in the airbox with the octagonal nut supposed to be hooked up to? Mine is open, with clamp on end and a VERY small hole at the end.

Can see clear to bottom of tank with flashlight - totally clean.


Also released the petcock (was sealed for nylyon), and flow could be clearly heard bubbling through.

Can you take a picture of that line? Let me know when you give up, trailer ready!

I wondered about that hose allso until I looked and all four were the same...two 416's and two 520's....soooo I guessed thats the way they are suposed to be.

Still at a loss on which hose you are talking about. There is one which is large and that is the air intake from the blower housing. The second is smaller and that is for the breather. It shouldn't be restricted at all, so if you have a picture that would be helpful.

The hose is conected to a brass fitting on the underside of the bottom half of the air cleaner housing it's only about 1/8 th id. It lays across the top of the motor towards the battery. It's hard to see, unless you remove the air cleaner bottom . The end hangs loose and looks like it was connected somewhere and broke off, at least that's what I thought when I firt saw it. Still don't know what it is for but all mine are th same I'm at work so I can't send a picture ..but I don't see it haveing anything too do with the fuel flow

Karl - guess I should qualify the word "donate"

Dual Wheels - amazing thanks for saving a possible hair-raiser in thinking I pulled something out.

Is totally removing / replacing that screw safe for a noob like me? Worried about:

1) Anything falling out
2) Setting it back once done