poor throttle response on 550

[bahmi]

540 PTO rpm mark is around 1600rpm on the 550. When I'm throttling down, I find that once I hit around 1200 rpm my tractor wants to lose rpm's down to 600 rpm. It's like my fuel delivery below 1200 rpm is less efficient or something suggestive of that.
I maintain that despite a rebuild on the carburetor, the tractor is simply NOT running well, especially around 12-1400 rpms. I've done everything necessary but at idle of around 1000 rpm, I'm getting some subtle popping and the engine just seems "off". Where does one start to get this under control? Just seems too irregular.

 

[RCP]

It is likley that you have a governor issue, either adjustment, binding or internal issues.

If you search through the archives you will find many good explanations on trouble shooting governors.

Good Luck
Rich

 

[Wayne Six]

Sounds like you may have two problems working against you. The governor is one that you need to check out for sure, but that subtle popping when idling at 1000 rpms sounds like you may have another problem working there, too. First question would be, did you have this problem before the carb rebuild and if so, second is is it now better or worse than it was and third would be...how much confidence do you have in the person that did the rebuild.
Had a similar problem with my '67 550....has a Marvel Shebler TSX 811 on it. Rebuild kit only had the float valve and seat in it, no mixture valves or seats. A variety of carb cleaner just didn't seem to do the job, so I polished the ones that were in there with a tooth brush and tooth paste, very very carefully...used round wooden tooth picks and bamboo skewers to work into the seats....and of course flushed and flushed with the carb cleaner....gentle is the key, you don't want to take off any brass, just some of the tarnish... My idle mixture screw now peaks the rpms at just over 1 and 1/4 turns and the high speed mixture screw now peaks out at about 1 and 3/4 turns...and no more of that random popping when idling.

 

[Dick W.]

That popping at idle could be that your timing is too far advanced. Check the point setting and then use a timing light. The timing can be advanced from what the book says, but too far and it will pop at idle.