YS Engines Support Direct support from YS Performance Engines by Dave Shadel

ys 91AC quitting

Old 05-17-2008, 07:32 AM
Thread Starter
Join Date: Jan 2007
Location: Bridgewater, VA
Posts: 116
Likes: 0
Received 0 Likes on 0 Posts
Default ys 91AC quitting

I have a YS 91ac mounted inverted that I purchased as part of a used airplane package. The person I purchased it from had it for aprox. 1 year, never flew or started it. It looks like it was flown by the first owner but i have no history. I have a fuel set up with two "T" fittings, using YS 20/20 fuel and the engine seems to be getting proper compression. Here is the problem. When I start it with the glow plug on, it will run, If I take the glow plug off when the engine is less than half throttle it will quit immediately, if the engine is running above half throttle it will continue to run but sputter out when it is bought below half throttle. I am letting it warm up with the plug on and letting it build compression then slowly raising the throttle. The screw that is on the underside of the engine was recessed a bit so I set it flush with still no luck. Also tried many combinations of high/low setting..........Any ideas??!!

Also-what is that screw for on the underside of the engine which is supposed to stay flush and what is that indicative of in an engine when it dies immediately upon removal of the glow plug? Thanks for any insight...

Old 05-18-2008, 09:48 AM
HankScorpio's Avatar
Join Date: Oct 2006
Location: Melbourne, AUSTRALIA
Posts: 32
Likes: 0
Received 0 Likes on 0 Posts
Default RE: ys 91AC quitting

1). Have you tried a new glowplug?
2). You mention the problem when glow-power is disconnected, what is the behaviour of the engine as you throttle up and down if you have the plug still connected to glow-power?

Old 05-19-2008, 04:43 PM
Troy Newman
Senior Member
Join Date: Dec 2001
Location: Goodyear, AZ
Posts: 2,429
Likes: 0
Received 3 Likes on 2 Posts
Default RE: ys 91AC quitting

What you describe is a rich mixture. The pressure regulator is the screw you are talking about on the under side of the engine. This adjustment is "IN" or CW for lean and OUT or CCW to richen. So if your screw was recessed slightly and you opened it up CCW rotation you richened it even more.

A new glow plug can be an issue as well.

Please go to this site for some details on how to operate this engine.

Troy Newman
Team YS

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.