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Texaco Running Steady

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Texaco Running Steady

Post  Iceberg on Sun Jan 13, 2019 4:50 pm

I have a Texaco in very nice condition. However it runs for maybe one minute then sort of fans down. I need to adjust needle valve a bit then runs ok for 30-40 seconds. Same thing happens again. I opened cleaned. Put new Venturi gasket. Blew all our with compressor. Put new puck up tube with spring. Why is there inconsistent running? I even put new cylinder and piston but that didn't change much either. Fuel related but why?
Thanks Iceberg
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Re: Texaco Running Steady

Post  Mudhen on Sun Jan 13, 2019 5:41 pm

If after you tune the engine it begins to reduce rpm on its own, then it means the crankshaft to crank case fit is too tight.
To solve the issue. Start the engine, leave the glow plug clip attached.
Tune it to a medium rpm, let it run for 15-20 seconds, then detune it to a slow rpm and let it cool down. Tune it again to a medium rpm, then let it cool
Do this for about two or three full tank runs.
After, start the engine, tune it to peak rpm for about ten seconds, then detune it, as before.
It should loosen up after five or six runs.
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Re: Texaco Running Steady

Post  RknRusty on Sun Jan 13, 2019 10:25 pm

Hi, Mud.
My first thought was the tiny flat-ring gasket on the venturi tube's tip may be leaky. When the fuel level drops below the tube and where it fits into the air intake hole, air leaks causing the fuel's head pressure to change.
Just guessing.
Rusty

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Re: Texaco Running Steady

Post  Iceberg on Sun Jan 13, 2019 10:51 pm

Hi Rusty
I added a second venturi gasket already but problem persisted?

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Re: Texaco Running Steady

Post  getback on Mon Jan 14, 2019 6:40 am

Mudhen wrote:If after you tune the engine it begins to reduce rpm on its own, then it means the crankshaft to crank case fit is too tight.
To solve the issue. Start the engine, leave the glow plug clip attached.
Tune it to a medium rpm, let it run for 15-20 seconds, then detune it to a slow rpm and let it cool down. Tune it again to a medium rpm, then let it cool
Do this for about two or three full tank runs.
After, start the engine, tune it to peak rpm for about ten seconds, then detune it, as before.
It should loosen up after five or six runs.
 I am sorry but by the time you do all that and it mite work (( i would take the engine completely apart and clean )) this means removing the crankshaft too !! Babe Bee .049 Also check the side to side play at the prop washer end of CS .


Last edited by getback on Mon Jan 14, 2019 6:42 am; edited 1 time in total (Reason for editing : add on)
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Re: Texaco Running Steady

Post  RknRusty on Mon Jan 14, 2019 12:26 pm

getback wrote: I am sorry but by the time you do all that and it mite work (( i would take the engine completely apart and clean )) this means removing the crankshaft too !! Babe Bee .049  Also check the side to side play at the prop washer end of CS .
Good point, Eric. The crank bushings could be worn down enough to be leaking crankcase pressure when it heats up. Have you noticed if it has a nosebleed? Like oil and fuel dripping from behind the prop-drive plate?

EDIT: Not really bushings, but the aluminum nose tube serves the same function.

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Re: Texaco Running Steady

Post  crankbndr on Mon Jan 14, 2019 12:44 pm

I have dissembled many NIB Cox engines and the crank is black from whatever, it needs a polish and the bore also.
You could maybe avoid pulling the crank by soaking the crankcase assembly in Hoppes 9 and flushing with fuel.
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Re: Texaco Running Steady

Post  Mudhen on Mon Jan 14, 2019 12:47 pm

If the engine tunes relatively steady, then begins to slow down on its own. It’s usually a friction problem.
It can be misleading because as the engine slows, it cools. When it cools, it wants to increase rpm. So the engine may sound, and act, as if it has an air leak, or fuel metering problem.
I don’t think this is a dirt issue or an end-play issue.
I think it’s a friction issue.
Cleaning the parts will have no effect. It needs a good break-in.
If it nose-bleeds, and the oil color is very dark, almost black, that will confirm the crankshaft fit is too tight.
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Re: Texaco Running Steady

Post  wmazz on Tue Jan 15, 2019 2:08 am

Mudhen wrote:If the engine tunes relatively steady, then begins to slow down on its own. It’s usually a friction problem.
It can be misleading because as the engine slows, it cools. When it cools, it wants to increase rpm.

This is interesting, I am anxious to see if a good break-in fixes the problem.
Does the propeller size affect the friction problem?

Is there a clear advantage to using Sig CHAMPION 20% or 25% ALL CASTOR
on Cox engines?

Mudhen wrote:
So the engine may sound, and act, as if it has an air leak, or fuel metering problem.

That's what I thought after I read the original post. I am curious if the
problem got worse after taking apart the engine.

Iceberg wrote:
I added a second venturi gasket already but problem persisted?

Why replace the venturi o-ring? or double it up. Did it look deformed?

I have always flat sanded the rear of the crankcase to eliminate a vacuum
leak, and replace the gasket if it is damaged.


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Re: Texaco Running Steady

Post  Iceberg on Tue Jan 15, 2019 4:01 am

I added the other venturi gallery wondering if there might have been a vacuum leak i added with existing making two of them definitely no leak there. Didn't change the "fanning" I have pulled apart yet but will to bleak. However didn't feel right? I'll be sure to let all know soon.
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Re: Texaco Running Steady

Post  Iceberg on Tue Jan 15, 2019 7:28 am

Hi Gents
I opened the tank to disassemble and clean all. Found that the fuel line had risen up in the tank. Because fuel line was new that I replaced it was so stiff it lifted up in the tank. I guess that was why it died after 1 minute. I'll do a test run in a day or so to see if being forced back to 8 oclick position fixed it. I'll be sure to let v all know. Thanks for input.
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Re: Texaco Running Steady

Post  Levent Suberk on Tue Jan 15, 2019 7:50 am

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Re: Texaco Running Steady

Post  RknRusty on Tue Jan 15, 2019 9:41 am

Sounds like you got it, Ice.

If it still does it, take that dang tank off and replace it with a backplate and an external tank, just as a test. That should eliminate all of the problems that make the integral-tanked engines so maddening. Those built-on tanks can make you waste more of your life than it's worth.
Rusty

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Re: Texaco Running Steady

Post  Iceberg Yesterday at 7:00 pm

Hi Guys
Did a test run last night with the motor. It ran 4 minutes on just Uber two turns on the needle. It held poetry good but still slowed a couple times a few hundred rpm then sped up again. I'm pleased it for fire minutes without stopping. I was told a Texaco might run 5-6 minutes. Anyone else got a comment?
Thanks
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Re: Texaco Running Steady

Post  Cribbs74 Yesterday at 7:02 pm

What size prop are you using?
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Re: Texaco Running Steady

Post  Iceberg Yesterday at 7:04 pm

6-4 Cox grey one
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Re: Texaco Running Steady

Post  Cribbs74 Yesterday at 7:30 pm

Iceberg wrote:6-4 Cox grey one

It’s supposed to swing a larger prop. Less RPM = better fuel economy.

The instruction sheet says 7Dx3.5P for a 5-6 min run time.
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Re: Texaco Running Steady

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