Generic gasoline engine tuning question

284 International · Jun 28, 2010

Hi, I have a gas IH 284 that really lacks power. When it attempts to pull a load (even starting itself out with no implement or trailer) the engine bogs, stumbles, and runs roughly. With no load, it runs smoothly, but it is difficult to throttle up: opening the throttle, even with no load, makes it stumble.

I have replaced the spark plugs and fuel filter. The spark plugs were sooty and dark black (including the new ones after less than an hour of use), and the fuel filter was free-flowing. I have replaced the air filter, and even tried it briefly without the air filter, all for no change.

I'm sure these symptoms mean something to someone with more knowledge than me, but I'm out of ideas. What should I try next? Thanks in advance.

RavensRoost · Jun 28, 2010

Carb may have "junk" clogging a jet. Junk can be dirt, rust, varnish, or other stuff.

284 International · Jun 28, 2010

There is no visible smoke that I can tell. That doesn't mean it's not there, obviously, just that I haven't seen it. The exhaust is re-routed to exit under the tractor, so it's difficult to see. When cold, it won't start or even run once started at anything other than idle. I need to let it idle for 4 to 5 minutes in order to throttle up. Throttle up unless done EXTREMELY slowly results in a popping death of the motor (it surges a bit, pops, then dies).

Will changing the float height affect the richness of the mixture to this degree?

Egon · Jun 28, 2010

Make some adjustments on the carb jets.

284 International · Jun 28, 2010

Egon, sorry to sound ignorant, but I don't have a service manual. How do I change the jetting? Does the entire jet get replaced, or is there a mixture screw?

LD1 · Jun 28, 2010

I am by no means an expert but it sounds to be like a governer problem.

I am not familiar with the 284 but trace your throttle cables from the lever and from the carb. They should lead you to the governer, which could have some levers and springs. Make sure that the springs arent missing/unhooked and that everything looks ok.

284 International · Jun 28, 2010

The governor theory is interesting. How would that make it run rich? When the tractor is driving, if there is ever any change in load, it bogs as the governor opens the throttle. I don't know how to isolate the trouble, but will check the governor.

Egon · Jun 28, 2010

How do I change the jetting? Does the entire jet get replaced, or is there a mixture screw?

I'm not familiar with your carburetor so there are two of us. Usually there are two jets, idle and high speed jet. They are usually little grub screws going through a spring. Some you turn in for more fuel, others you turn out. I'd suspect yours turn out. Most have a proper operating range one and a half turns from closed??

If you adjust on these screws always keep track of what you did or you will end up like I always do not knowing where I'm at and having to start from scratch. Sometimes opening them a little will let junk out of the jet or make up for varnish etc.

A carb kit usually has new jets and seats.
Also go easy on them when closing as they can be damaged.

I'll try and find a picture to post.

http://faq.ninja250.org/wiki/How_a_carburetor_works:_Carbs_explained

LD1 · Jun 28, 2010

284 International said:
The governor theory is interesting. How would that make it run rich? When the tractor is driving, if there is ever any change in load, it bogs as the governor opens the throttle. I don't know how to isolate the trouble, but will check the governor.

On the same tolken, a plugged jet in the carb wouldn't allow it to dump more fuel and make it run rich either. If it is indeed running rich, that means either too much fuel or too little air. But the symptoms you descrive sounds like a governer(aside from the black plugs). Not wanting to throttle up and bogging severly under load sure sounds like a governer.

But I am no expert. I am better with autos and they dont have them. I cant tell you what to look for or how to adjust, just give it a once over and see if everything looks in place.

284 International · Jun 28, 2010

How would the governor be different than the regular hand or foot throttle? Again, I'm semi-ignorant of the operation of the mechanisms at play, but know they exist. What can I do to test or inspect the governor? What should I be looking for?

I'm willing and able to rebuild the carburetor. I am experienced and comfortable with motocross dirtbikes and their components, but while the fundamental principles are the same, the intermittent, highly variable rpm range is a lot different than the constant load and steady rpm of a tractor. Where can I get a carburetor rebuild kit?