YS91FZ problems  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> YS Engines Support >> YS91FZ problems
Page: [1]

Login
Message << Older Topic   Newer Topic >>
YS91FZ problems - 7/19/2003 7:32:03 PM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		I have a problem with my YS91FZ. It will suddenly go to idle in flight. Sometimes it will come back after a few seconds by returning the stick to idle and advancing it. At others times it will load and stumble when the throttle is advanced. In the session before the most recent one, fuel was pouring out of it when I landed indicating a leak past the plunger. I took the regulator apart and removed the spring and plunger and flushed it with fuel, although there no evidence of dirt, and reassembled it. The regulator was set flush and the main needle set initially open 1 1/2 turns. The engine was run and the main needle set and a minor adjustment made to the regulator. With 15% Omega and a 14x8 APC rpm was initially ~9700 and then settled back to ~9300. Idle, transition and top end were fine. At the field I had one normal flight and in the typical pattern of the past year, the engine repeated its previous behaviour in the second flight. The engine is about two years old but I haven't been able to get much time on it although I have lots of practice landing without power. (One significant crash too.) Before the current problems developed the engine was always vague on the main needle.

The diaphragm, plunger and spring have been replaced. The airbox was warped and is now sealed with high temp silicone. The check valve functioned normally but was replaced anyway. The system holds pressure for prolonged periods. Valve clearances has been set to specs. A new OS#F plug was installed. A fuel filter is used and is clean. The fuel runs fine in a 91AC. The carb was disassembled in the recent past and I found a piece of debris that I thought might have been moving around in the groove and obstructing fuel flow. Removing it made no difference.

After the engine went wonky on the second flight yesterday the main needle response was irregular and it would momentarily drop rpm in ground running at full throttle. At one point fuel was dripping from it. The regulator screw was run in until it bottomed and backed out to flush and the main needle set to 1 1/4 open. This stopped the fuel leak and once again the engine was fine - until a few minutes into the next flight and we were back to the same behaviour that has plagued this thing for the last year. Perhaps it had just cooled off and healed itself temporarily.

To eliminate question about mechanical operation of the throttle the servo and receiver were both swapped out. The transmitter runs several other models. The throttle arm is not slipping. As you might gather, this engine has more than sucked the joy out of flying.

Can you offer any help?
[URL=http://members.accesswave.ca/~parklane/Home.html]http://members.accesswave.ca/~parklane/Home.html[/URL]
       Post #: 1

YS91FZ problems - 7/19/2003 7:48:38 PM   
Dave Shadel


 

Posts: 5407
Joined: 4/9/2002
From: Gardnerville, NV, USA
Status: offline 		From the stated age of the engine, it is possible that the gas port mod has not been done to it. It certainly has the symptoms of an engine that needs it.
It should be looked at. Please send it in as soon as possible.

YS Service
1295 Industrial Court
Gardnerville,
Nv 89410

Phone 775 782 4562

(in reply to John Hawkins)
       Post #: 2

YS91FZ problems - 7/19/2003 8:18:24 PM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		Dave, OK, will do. It is past anything I can do to solve the problem.

(in reply to John Hawkins)
       Post #: 3

YS91FZ problems - 7/24/2003 2:00:45 AM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		Dave,

The engine is on the way to you for service. Can you explain what the gas port mod is?

John

(in reply to John Hawkins)
       Post #: 4

YS91FZ problems - 7/24/2003 2:02:12 AM   
Dave Shadel


 

Posts: 5407
Joined: 4/9/2002
From: Gardnerville, NV, USA
Status: offline 		A series of holes drilled through the top of the piston behind the ring for better ring seal.

(in reply to John Hawkins)
       Post #: 5

YS91FZ problems - 7/24/2003 2:09:38 AM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		As I thought but wasn't certain. Is the ring tension purposely low?

(in reply to John Hawkins)
       Post #: 6

YS91FZ problems - 7/24/2003 2:19:05 AM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		As I thought but wasn't certain. Is the ring tension purposely low?

(in reply to John Hawkins)
       Post #: 7

YS91FZ problems - 7/24/2003 2:19:26 AM   
Dave Shadel


 

Posts: 5407
Joined: 4/9/2002
From: Gardnerville, NV, USA
Status: offline 		In an engine that didn't depend on a regulator which is operated by crankcase pressure, it wouldn't matter, but ring leakage drives the regulator nuts! That is why I decide to start using it and the YS factory has incorporated it into all new production.

(in reply to John Hawkins)
       Post #: 8

YS91FZ problems - 7/24/2003 2:29:55 AM   
John Hawkins



Posts: 278
Joined: 6/8/2003
From: Halifax, NS, CANADA
Status: offline 		I can see where the case pressure would be all over the place and make for all sorts of trouble. Incidentally, is it possible for the case to hold enough pressure after shut down to unseat the plunger? Do the ports have any tendency to carbon up when using Omega? Sounds like a good application for a Dykes ring.

(in reply to John Hawkins)
       Post #: 9

Page:   [1]
All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> YS Engines Support >> YS91FZ problems
Page: [1]





Jump to:


Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Member Video Posts | RCU Video Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

© 2001 - 2007 24-7 RC, LLC, all rights reserved.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America

Kaango.com Classifieds

0.359RCU5