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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> 2 quick questions
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2 quick questions - 9/7/2005 3:10:26 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline 		Would an air leak on the intake side of a four stroke engine cause the engine to idle really high like 3800 rpm and can JB Weld be used as a suitable repair?
       Post #: 1

RE: 2 quick questions - 9/7/2005 3:19:47 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		The air leak itself would not cause the high idle, but it might keep you from getting the engine to idle at a lower speed. So in a way, I guess the leak might cause the high idle.

JB Weld? Depends on whatyou want to repair. If you have a leak from a joint RTV is better because you can take it apart again if needed. If you are repairing a broken casting it could be the only way other than buying a new part. You need to be more specific on the repair.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to larksrc)
       Post #: 2

RE: 2 quick questions - 9/7/2005 4:30:37 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline 		Actually its an small ckarck on the head just beneath the intake valve assembly. The reason I ask about the jb weld is beacause I would like to avoid spending $110 on a new saito 180 head if possibe.

(in reply to William Robison)
       Post #: 3

RE: 2 quick questions - 9/7/2005 4:31:38 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline 		oops, I mean crack

(in reply to larksrc)
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RE: 2 quick questions - 9/7/2005 4:38:27 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline
quote:

but it might keep you from getting the engine to idle at a lower speed


yep cant get to idle below 3800 rpm with out stoping after 40 seconds. Fiddling with the needles doesnt seem to help. Took the engine out of the airplane and noticed the crack.

(in reply to larksrc)
       Post #: 5

RE: 2 quick questions - 9/7/2005 5:00:53 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		I'll guess you meant under the intake valve rocker gear. Under the valve would be inside the cylinder.

Is this crack in a place that's covered at least partially by the rocker pedestal? If it is you might try the RTV, but if you can get the JB Weld in and keep it there it would probably work better.

Or is it the rocker pedestal itself? A lot less money, about $18 as nearly as I remember.

But there's the question implied: Why did it crack? If you don't correct that it wont hold, no matter what you use.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to larksrc)
       Post #: 6

RE: 2 quick questions - 9/7/2005 5:11:42 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline 		It must have gotten damaged after my crash. I had to repalce the bent valve and the spring but this is the first time Ive noticed the crack. Its on the top of the head on the intake side just foward of the glow plug. I have been told that jb weld can be used to fix just about anything.

(in reply to William Robison)
       Post #: 7

RE: 2 quick questions - 9/7/2005 6:58:09 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Lark:

You will want to pull the intake rocker pedestal off again, check carefully around the periphery of the guide, be sure the base aluminum is still pressing against it. If the crack extends to the bronze part you will need to be sure it is still held firmly. And you'll need to pack the JB Weld into the crack at any place you can.

If you find the guide is loose (the spring will have to come off to check) see if you can pull it out of the cylinder. A thin smear of the JB Weld round it will let you glue it back in place. To be sure it's aligned properly put the valve and valve spring back in, the valve will center on the seat and hold the alignment of the guide. Screwing the pedestal back on will help hold it in place too.

Before you put the pedestal back on, of course you will pack as much JB Weld into the crack as you can, then the valve and spring, and the pedestal and set it all aside to allow it all to cure.

Try to keep thje glue off the pedestal's base. If it doesn't work you don't need to buy another pedestal.

It's worth a try, I wish you good results.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to larksrc)
       Post #: 8

RE: 2 quick questions - 9/7/2005 11:59:47 AM   
Dr1Driver



Posts: 3589
Joined: 7/25/2002
From: Spartanburg, SC, USA
Status: offline 		If the engine was hit hard enough to crack the head, I'd thoroughly inspect it for other damage.

Dr.1

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There's a Hun in the sun!

(in reply to William Robison)
       Post #: 9

RE: 2 quick questions - 9/7/2005 12:26:14 PM   
beelzebubishere


 

Posts: 1391
Joined: 8/29/2005
From: Grovetown, GA, USA
Status: offline 		Is your model, all the electronics, and the rest of the engine worth more than $110.00?
Probably so....replace the head. An airborne catastophic failure, or even a flame out, at an inopportune time due to a known fault(cracked head) ain't worth the possible results. Not to me anyway.

(in reply to Dr1Driver)
       Post #: 10

RE: 2 quick questions - 9/8/2005 1:33:53 AM   
larksrc


 

Posts: 122
Joined: 10/14/2003
From: Lake Charles, LA, USA
Status: offline 		Success! Filling the hole with the jb weld fixed the air leak and it now idles at 1900-2200 rpm. Now all I have to do is reset the needles and I will be ready to go. Thanks for the advise Will.

(in reply to beelzebubishere)
       Post #: 11

RE: 2 quick questions - 9/8/2005 2:03:58 AM   
William Robison



Posts: 20269
Joined: 11/10/2002
From: Mary Esther, Florida, FL, USA
Status: offline 		Lark:

Glad it worked.

Bill.

_____________________________

Real Airplanes have Two Engines
AMA 25139 - More than 40 years.

(in reply to larksrc)
       Post #: 12

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