Super Tigre 90: Fuel leak when running    Gallery
View related threads: (in this forum | in all forums)

Logged in as Guest



Users viewing this topic: none
    Search This Thread  
 
Printable Version


SAB Goblin 770 Helicopter - RTF
Seller:  mariogonzales
Details:   $2,500.00   |  5/14/2013   |  Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> RC Airplanes >> Beginners >> Super Tigre 90: Fuel leak when running
Page: [1]

Tower Hobbies Get Coupon Codes Brands  
Login
Message << Older Topic   Newer Topic >>
Super Tigre 90: Fuel leak when running - 8/17/2011 1:34 AM   
jigeye


 

Posts: 510
Score: 135
Joined: 12/27/2005
Last Login: 2/24/2013
From: Germantown, TN, USA
Status: offline 		Greetings:
I have a ST 90 I took apart to clean and reassembled. I also installed a new ring. I am having problems with fuel leaking when breaking the engine in. I cannot tell exactly where it is coming from, however, it is not coming from where the engine and muffler meet. This leaves only two other places. Either the gap as shown in the photo or the back end of the engine where the 4 screws are. My guess is the gap. The following questions will help me in solving this issue:
1. Is the head oriented correctly?
2. Is 4cm the correct gap space between the head and the engine with the head properly installed?
3. Is the cylinder sleeve properly aligned? I think it is as the pix show.

Any other advice would be appreciated. Need to solve this.
Mike


Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize
Click to see fullsize image.
Click for fullsize


Hide Signatures
       Post #: 1

RE: Super Tigre 90: Fuel leak when running - 8/17/2011 3:07 AM   
jester_s1


 

Posts: 3802
Score: 233
Joined: 12/17/2006
Last Login: 5/24/2013
From: Fort Worth, TX, USA
Status: offline 		I just looked at my G90 and the head gap looks the same. I can't tell how your sleeve is oriented, but if the exhaust lines up you're good. Are you getting raw fuel or oily burned residue leaking out?

One tip about Super Tigres if this is your first one is that they very often have loose bolts from the factory. I see you've had the head off so you should know if the head bolts were too loose, but the backplate is a common loose spot too. Check all of your bolts and clean the engine thoroughly. You should be able to tell very quickly from there on where any leak is coming from.

_____________________________

For me, an ARF is an airplane that someone else just crashed.

Hide Signatures

(in reply to jigeye)
       Post #: 2

RE: Super Tigre 90: Fuel leak when running - 8/17/2011 4:46 AM   
downunder



Posts: 4364
Score: 123
Joined: 10/10/2002
Last Login: 5/20/2013
From: Adelaide, AUSTRALIA
Status: offline 		The head is oriented correctly with the slightly longer head finning to the rear (altgough it wouldn't really matter if it was 180 off). The liner is fitted correctly (there's obviously an alignment pin) but the liner would protrude above the crankcase by 4mm, not 4 cms, so you were correct the first time you showed the measurement . The gap between the head and crankcase when the head is fitted is likely on the order of 2mm because the head fits down over the liner with the piston coming almost flush with the top of the liner at TDC.

If the head screws weren't tighten correctly then it's possible to warp the head and get leakage past the head shim. The screws should first be tightened until they just barely nip then tighten a small amount in several stages until they're nice and firm. With only 4 screws, tighten them as pairs 180 apart. You can check for leaks by using gas leak detector fluid or a weak solution of dishwashing liquid in the gap between the head and crankcase.

Fuel can sometimes spit back out of the carb and give the appearance that you have a leak somewhere.



Hide Signatures

(in reply to jester_s1)
       Post #: 3

RE: Super Tigre 90: Fuel leak when running - 8/17/2011 8:04 PM   
opjose



Posts: 12255
Score: 280
Joined: 11/26/2005
Last Login: 5/24/2013
From: Poolesville, MD, USA
Status: offline 		Downunder's responses are always excellent...

One area that the ST's have a tendancy of spitting fuel from, is the carb barrel.

ST's carb has a big and visible rubber seal to help keep this from happening, but it is not very effective.

The carb can leak fuel prior to start that gets blown back, making it appear the engine is leaking elsewhere.

Also remember that the bearings are designed to purposely allow the flow of oil past them, so most glow engines will seem to leak a bit of fuel.
This is most obvious if you store your planes nose down ( as I do ). I frequently see a drop ready to fall from the front engines of the planes I have in storage.

BTW: That shim looks a bit gritty in the photo. Did you clean it up before re-installing the head?


_____________________________

Don''t worry, be happy and fly something!

Hide Signatures

(in reply to downunder)
       Post #: 4

RE: Super Tigre 90: Fuel leak when running - 8/17/2011 9:40 PM   
mudboger07


 

Posts: 195
Score: 100
Joined: 11/15/2010
Last Login: 2/22/2013
From: Arlington, TN, USA
Status: offline 		Jigeye were do you fly, I fly at Memphis Prop busters in arlington, drop me an email if ya cant get the st 90 going I might be able to help.

_____________________________

Ken
Club Saito #732

Hide Signatures

(in reply to opjose)
       Post #: 5

RE: Super Tigre 90: Fuel leak when running - 8/17/2011 10:31 PM   
jigeye


 

Posts: 510
Score: 135
Joined: 12/27/2005
Last Login: 2/24/2013
From: Germantown, TN, USA
Status: offline 		Ken,
Thanks. Yes I fly at propbusters. Been out of the flying hobby for a couple of years but rejoined the club. I appreciate your help.
Mike Ross

Hide Signatures

(in reply to mudboger07)
       Post #: 6

RE: Super Tigre 90: Fuel leak when running - 8/19/2011 4:39 AM   
cutaway


 

Posts: 1009
Score: 125
Joined: 6/26/2007
Last Login: 3/6/2012
From: Lake Worth, FL, USA
Status: offline 		There's a lot of combustion gunge along the cylinder/head mating surfaces. With good fit and proper torquing, those areas should look pretty clean upon disassembly...I'm just saying. I think your head was loose.

Hide Signatures

(in reply to jigeye)
       Post #: 7

RE: Super Tigre 90: Fuel leak when running - 8/21/2011 9:06 PM   
jigeye


 

Posts: 510
Score: 135
Joined: 12/27/2005
Last Login: 2/24/2013
From: Germantown, TN, USA
Status: offline 		Problem solved. As usual something simple. Made new gasket for exhaust manifold. The leak made it look like it was coming from the head. Shudda dun this first!
thanks for the replies.

Hide Signatures

(in reply to cutaway)
       Post #: 8

RE: Super Tigre 90: Fuel leak when running - 8/23/2011 1:55 AM   
tigrejohn


 

Posts: 93
Score: 100
Joined: 8/28/2008
Last Login: 4/15/2013
From: corona, CA, USA
Status: offline 		Suggestion: ditch that gasket and get a metal to metal joint with sealant. I have and read times where it has occurred where they have lost the muffler in flight. Appears that vibration compresses the gasket after a number of runs due to the vibration. Either you you use high temp silicone as a sealant without gasket or check your muffler bolt tightness after every flight to avoid the mess and/or losing your muffler. If your want to stick with gaskets, use Nylock nuts; you may have the mess but you will keep your muffler.

Hide Signatures

(in reply to jigeye)
       Post #: 9

RE: Super Tigre 90: Fuel leak when running - 8/23/2011 7:13 AM   
jester_s1


 

Posts: 3802
Score: 233
Joined: 12/17/2006
Last Login: 5/24/2013
From: Fort Worth, TX, USA
Status: offline 		It's probably not vibration that loosens them but rather thermal cycling. The bolts will stretch as the aluminum heats up then return to normal, but the gasket material won't. If you're fastidious about the black oil, a thin paper gasket (copy paper works) won't compress enough to hurt anything. But I use hi temp gasket maker and a drop of locktite on the bolts torqued about 1 turn past tight, and I haven't had any problems.

_____________________________

For me, an ARF is an airplane that someone else just crashed.

Hide Signatures

(in reply to tigrejohn)
       Post #: 10

Page:   [1]
All Forums >> RC Airplanes >> Beginners >> Super Tigre 90: Fuel leak when running
Page: [1]





Jump to:


 
Google 



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

Photo Gallery | Instructor Search | Field|Track|Marina Search

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

SITE MAP!   : :   FORUM RULES

RC Universe is a service of Internet Brands, Inc. Copyright © 2001-2013.

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


0.328RCU1