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RCV 91 CD Problem

Old 12-04-2008, 06:34 PM
  #1  
Radspit
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Default RCV 91 CD Problem

I purchased a 91 CD about three years ago and it has sat in the box until three weeks ago when I fired it up for the first time. I am running cool power 15% fuel and a 14 x 6 prop and a Keleo scale exhaust. Well the engine would not run worth beans. I had it rich and if I took the glow igniter off it would die instantly wether at low or high rpm's. I put in a new OS four stroke plug, no improvement, bought a brand new gallon of fresh fuel, no improvement. Took the scale exhaust off and put the stock muffler on still the same. It will not run without the igniter energized at all times. This one has me stumped. Any idea's ? Rad
Old 12-05-2008, 01:17 AM
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tadawson
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Default RE: RCV 91 CD Problem

Have you tried leaning it out some? It sounds like it is nothing more than way too rich . . .

- Tim
Old 12-05-2008, 01:30 AM
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saramos
 
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Default RE: RCV 91 CD Problem

15% is too much nitro. RCV recommends 10% nitro and 15% oil with no more than 6% if it being castor. Not sure this is your specific problem, but I'd stick to the recommendations especially when breaking in.

Scott.
Old 12-05-2008, 10:49 AM
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Radspit
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Default RE: RCV 91 CD Problem

Yes I have tried leaning it and I get the same result. Rad
Old 12-08-2008, 07:36 AM
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keithlawes
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Default RE: RCV 91 CD Problem

Hi Rad

Its Keith Lawes from RCV Engines here hoping to help out!!

Will the engine not even run flat out with the plug de-energised?

1/ Could you give me an RPM figure with the engine flat out. If you haven't run the engine in please put at least 10 minutes on it before doing this at lower throttle, then stop it to let it cool, then start it and put it flat out.

2/ Could you also check the valve timing. To do this remove the exhaust and carb, then put the engine to top dead centre between inlet and exhaust. You do this by aligning the key on the prop driver vertically downwards (if port is not visible at all you are at TDC between comp and power strokes so turn the crank 360 degrees). At TDC you should have equal amounts (a couple of mm) of port visible in the exhaust and inlet ports (this is the inlet/exhaust valve overlap, same as on a conventional 4 stroke). If theres significantly more port in one than the other then the engine will need to be retimed. This is straightforward but we'll worry about it if its the problem (which I think is unlikely)

Thanks

Keith


Old 12-09-2008, 05:34 PM
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Radspit
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Default RE: RCV 91 CD Problem

Thankyou Kieth, I will be going down tomorrow for another try and will take a rpm reading for you and then take the engine out of the aeroplane and check the timing as you suggested. I have a half gallon of fuel through the engine as of now. I can remove the igniter at 3/4 or above throttle and it keeps running but anything less and she stops instantly without the igniter. Thankyou again and I will report on tomorrows findings. Rad
Old 12-10-2008, 11:34 PM
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Radspit
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Default RE: RCV 91 CD Problem

Keith, Here are my findings. Max rpm I could get was 8650 with a 14X6 top flite wood prop on cool power 15% fuel. Still could not remove igniter below 3/4 throttle without it dying instantly although it did burble just a bit. I checked the timing as you asked and it appears that with the woodruff key at the 6 o'clock position there is a slight gap ( 2mm ) in both the intake and exhaust. What next ? I have a 3000mh onboard igniter battery and as long as I keep it energized it runs and flies just fine. Rad
Old 12-11-2008, 07:05 AM
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keithlawes
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Default RE: RCV 91 CD Problem

Hi Rad

Timing sounds spot on and RPM is reasonable. You have obviously tried the mixture. But maybe have one last go to see if the idle needle has any affect.

As you screw the idle needle in the part throttle mixture will become leaner and leaner, and should help to keep the glow lit. But if you screw it in too far the part throttle mixture will become so lean the engine will not run, even if the glow is connected. So please go through the following procedure.

With engine stopped turn idle needle in 1/8 of a turn.
Turn the main needle at least one turn beyond its normal position
(This is because the turning in the idle will lean out the part throttle mixturem, but will also affect the full throttle mixture slightly so need to make sure the engine has enough fuel to throttle)
Start engine.
Take to full throttle and lean out the main needle in the normal way to get peak RPM.
Remove the glow and close the throttle and see if engines part throttle behaviour is improved.

If behaviour is improved stop and close the idle needle another 1/8 and repeat the procedure. As noted above always ensure you richen up the main before throttle up as idle needle does have some effect on full throttle mixture.

You will know if you have closed the idle needle too far as the engine will either not start at all, or it will die lean when you open the throttle, no matter how rich you set the main.

If this has no effect then will need to send to our service agent in the states, Bill Jensen. He is a very good man and will sort your problem! His website is:-

http://www.bj-model-engines.com/

Start by forwarding him this thread.

Many thanks

Keith

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