Variable RPM & "Smokiness"

[metallurgist]

My 1986 model 7035 starts very easily (1-2 a pull today) after several prime pumps and operates well but only intermittently. I completed the lawn but barely. The last time I used it was about 2 seasons ago & it acted this way then. Today for the 1st 25% of the job it ran at low RPM and smoked as in running rich. This condition causes chute & bag clogging. Then for about 50% of the job the RPMs returned to normal and the smoking stopped like the rich condition ended(?). Then, the initial conditions returned until finished. I'm bagging BTW. Any thoughts? Thank you.

 

[rarebear]

Have you checked your air filter?
I change mine out for a cleaned filter every time I mow..
Our GA. clay on dry days is really bad..

 

[lewb]

Might also have a plugged exhaust,

 

[beg]

take the carb off and clean it I bet you have a sticking needle valve due to some gook in the seat.

 

[bwright1818]

I had a commercial F engine that did this. I cleaned the carb, which looked great, cleaned the ports, air filter, etc. No change. Finally, I REPLACED the needle and seat assembly with a new one and it was a like-new machine, after that. Night and day difference. Now, I have another F that just started this, yesterday! I think I know what I'm gonna do....