Fs90r wont take throttle

Gramp75

Forum Newbie
Joined
May 31, 2022
Threads
3
Messages
9
IAdjusting jets no help it runs starts but wont take throttle. Valve lash looks good. Right now im running bare carb covers and air cleaner missing. Opened carb all looks cleangood. Too things i noticed. Carb is spitting and when idling its rough like rich but every so often it smooths out for a second only. No idea what the bottom diaphram thing does one carb with big hose to motor? Also dont know jet settings. And whats that doohickey on top of gas tank under carb?
 

Attachments

  • 20220531_164307.jpg
    20220531_164307.jpg
    490.9 KB · Views: 4
Last edited:

Gramp75

Forum Newbie
Joined
May 31, 2022
Threads
3
Messages
9
Have you checked the exhaust screen?
The doohickey is the tank vent.
It runs shoots smoke out exhaust. Th priblem i think is the gas spitting outcarb at idle. Idle is consistant but acts like every other spark fire. Other thing is jets dont effect it but carb is clean inside
 

StarTech

Lawn Royalty
Top Poster Of Month
Joined
Feb 19, 2020
Threads
75
Messages
10,111
First you should not be able to adjust much with the limiter caps in place. How is the metering diaphragm? Is it stiff?

Also have you adjusted the valves? And have you checked the spark arrester?
1654206648909.png
 

slomo

Lawn Addict
Joined
Jul 14, 2019
Threads
76
Messages
4,677
Pull the muffler. Clean out the exhaust port and muffler screen as suggested previously. Rebuild the carb.
 

Gramp75

Forum Newbie
Joined
May 31, 2022
Threads
3
Messages
9
I see no comments about carb spitting has to be valve timing or valve fault. Like worn guide? Or cam shaft defect? I may pull muffler for kicks. Who knows? Gaskets diaphrams are good. This unit looks like its got a million miles on it.
 

slomo

Lawn Addict
Joined
Jul 14, 2019
Threads
76
Messages
4,677

StarTech

Lawn Royalty
Top Poster Of Month
Joined
Feb 19, 2020
Threads
75
Messages
10,111

Hammermechanicman

Lawn Addict
Joined
Jan 10, 2020
Threads
49
Messages
3,485
If it is spitting back fuel at idle the first thing to check is the exhaust screen being plugged. On a 4 mix the next thing is valve adjustment. If engine has a lot of hours on it and not run hard enough to keep it up to temp it can be carboned up to the point intake valve not sealing properly. Stihl sells an expensive can of stuff that will decarbon an engine.
 
Top