M4900 Inconsistent Idle and Throttle Speed

[podzie]

Test driving an M4900 today and everything was awesome about the tractor...low hours, good tires, well tended to, you could tell.

But then I ran her up to 540 speed which I think was around 2400 or so. Every time I took my hand off the throttle, the RPM's would drop to between 1800-2000. I kinda figured it has to be some sort of linkage problem, right? I mean, I could throttle back up either by foot or hand, and she'd run perfectly until I let off.

Also, the dang thing won't find a good idle. If I back off throttle all the way, sometimes it would drop to 1500 RPM, sometimes 1300, heck sometimes 1000....but never to a consistent level, and never below 1000.

I guess my main concern for all this is that it would be a mechanical problem in the links and not a fuel pump problem.

Any thoughts?

 

[ajenkins]

Sounds like the throttle linkage is loose. My M4900 idles at abt 1000 RPM and has since it was new. Good Luck

 

[podzie]

I was told that the tech this morning said it was probably a rod which is either inside or part of the pump that needed cleaned. They said this happens to them when tractors sit up for a while.

Sound right?

I dunno. We'll see.

I'm pretty confident it's no big thing.

Thanks.

 

[rbargeron]

Have a look at the hand throttle lever - some have a jamb nut to adjust the friction at the pivot - might be as simple as tightening that nut a little so the linkage stays wherever you put it. That might stabilize the idle too. Anyway check that before diving deep.

 

[podzie]

Thanks for the input. I'll definately do that and report back.

 

[hill]

I added a few washers and some marine wheel bearing grease to attach/swivel points of the throttle linkage of my new B7800 because they looked like they MIGHT become sticking places once dirt, water, possible rust and general muck had built up as they inevitably do with time and use.

Some spray lubricant/penetrating stuff might quickly localize the problem if it's resulting from mmisbehaving external linkage.

 

[podzie]

PROBLEM SOLVED!

I don't know exactly where the linkage was binding, but the tech went through the thing, and lubed all the rods and joints, and Voila....she purrs like a dream.

I cannot believe how nice this machine is. The 5-cylinder is awesome, and the layout of these bigger tractors is VERY comfortable...like driving around on a big leather recliner!

I really feel a little guilty about buying it. It's just so nice for a boy that came up on a Massey 65.

I'll update with pics soon.