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MVVS 49

Old 05-08-2006, 01:06 AM
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rhk
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Default MVVS 49

Hi,
I recently mounted a MVVS 49, purchased from Morris hobbies ( when they were selling the same!) on a gee whiz bee. after i lost the slow speed needle valve on the MVVS 40. I broke the engine in using 20 % castor, and a 11 x 6 prop. For 3d flying i am using a 12 x 4 master airscrew prop.

The problem I am facing is that :

1. It cuts off immediately on transit from idle.
2. when i hold the plane vertical, the engine cuts off, even on high rpm. { the tank is mounted on the side of the airplane, at the level of the engine,and the plumbing seems fine. I did not experience the same problem using the 40.
3. cuts of after 5 mins in the air, and on landing can restart the engine with whatever fuel is present in the tank.( engine rpm = 12,000)

would appreciate any input towards solving this problem
Old 05-08-2006, 01:35 AM
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Default RE: MVVS 49

Hi Rajeev,


It is nice to see you here.

I would suggest you restart all over again.

Repeat the break-in on a test stand (can be a makeshift stand - a board with a slot and properly located holes, two full tanks) according to [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]this RCU thread[/link].

After that, use latex rubber foam around the fuel tank, to fully isolate it from the engine's vibration.
Make sure the pressure nipple of the silencer is open.

Make the adjustments of the needles (high speed first) with the plane in nose-straight-up attitude.


What silencer are you using?
Old 05-08-2006, 11:48 PM
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Default RE: MVVS 49

Dear Dar,
Thanks for your prompt reply, will try your suggestions this weekend.
I am using the tuned muffler with the engine, and I did check the pressure nipple, which appeared to be blocked ( when inserting a pin). The nipple was cleaned but the problem persisted.
Old 05-09-2006, 12:17 AM
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Default RE: MVVS 49

Rajeev,


Try connecting connecting a short silicone tube to the pressure nipple and blowing through it.

There should be a consistent - not intermittent airflow. Not massive.
The engine only uses less than 25 cc of fuel per minute and the nipple should pass enough air to replace the used fuel; much more isn't necessary.

The secondary needle may have to be closed - it is started at 1.2-2 mm from the throttle arm nut.
It will end up at less.
Old 05-09-2006, 10:28 PM
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rhk
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Default RE: MVVS 49

Dear Dar,
Flow through the pressure nipple is unobstructed. woll try resetting the low speed needle valve as suggested.
thanks.
Old 06-01-2006, 11:14 PM
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rhk
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Default RE: MVVS 49

Dear Dar,

tried resetting the slow speed needle valve but results were the same - 4 min fligt followed by a dead stick. Thought the engine was lean, so i richened teh mixture, but the result was the same. The slow speed needle valve is the old one( blunt tip) . I have now replaced it with the new one ( tapered tip) any suggestions as to the start point/settings ?
Thanks
Rajeev
Old 06-01-2006, 11:16 PM
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Default RE: MVVS 49

Dear Dar,

tried resetting the slow speed needle valve but results were the same - 4 min fligt followed by a dead stick. Thought the engine was lean, so i richened teh mixture, but the result was the same. The slow speed needle valve is the old one( blunt tip) . I have now replaced it with the new one ( tapered tip) any suggestions as to the start point/settings ?
Thanks
Rajeev
Old 06-01-2006, 11:29 PM
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Default RE: MVVS 49

Rajeev,


The initial starting position is 2 mm out, but experience shows me that beginning 1.2 mm is better, since the final position ends up as .5-1.0 mm.

Check if the low-speed needle is not backing out of position (opening), from the engine's vibration.
If it does, make sure it doesn't...

Filing the ends of the spring flat and using some irrigation sealing Teflon tape, on the nozzle thread helps a lot.

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