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HomeAircraftHelicopterGasser Model RC HelicoptersOther › who's clever enough to work this one out
04-12-2010 01:38 AM  8 years agoPost 1
jprconstruction

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Nottingham,uk

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zenoah 26cc in predator
absolutely no pop from engine of any kind.
The following checks are not necessarily in order as checked.
fuel mix is ok i tried it in other zenoah gasser 40:1
plug ok,sparks good when holding on head out of hole.
swapped plug from known running other zenoah
swapped known working carb from other zenoah
fuel getting through,piston looks slightly wet when shining torch down spark hole after pulling over a couple of times.
tissue over spark hole tested fuel present,tissue slightly damp.
complete carb clean and needle reset as per walbro site.
compression very good.
no leaks from gaskets,used leak detecter spray to test.
put few drops of fuel down spark plug hole to bypass carb.no pop
pulse hole on crank case to carb clear, blew through to check.
muffler and manifold gasket tight.
checked kill switch not shorting all ok (would not spark anyway with shorting kill switch).
piston head smooth and clean.
head gasket and bolts perfect and tight,(checked torque).
still no pop or any sign of popping.
my level of engine knowledge.
25 years general tinkering with everything from cars to bikes to all rc petrol and nitro engines,i recently changed my supercharger and set it up in my seadoo rxpx.complete gearbox stripdown and rebuild on alfa romeo 147 gta.ect ect.so not unfamiliar to engines.
I am at a complete loss with this zenoah,absolutely baffled beyond belief.
Who out there is the dogs bollocks.
I bow to who ever can pinpoint this.
Thank you in advance.
regards john

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04-12-2010 01:43 AM  8 years agoPost 2
george0079

rrElite Veteran

USA

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What about the ignition timing?

Is it firing at the right time?

Hell... I can fix that.
Uh oh..
Nope.
It's ***ked!!!
RE-KIT!!!!!

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04-12-2010 01:50 AM  8 years agoPost 3
jprconstruction

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Nottingham,uk

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ignition timing
hi i did not think you could change the ignition timing as the maneto is bolted tight in place with no visual signs of adjustment.
thanks for the reply
regards john

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04-12-2010 01:52 AM  8 years agoPost 4
ka6fty

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Sacramento, Ca.

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What is the history on the engine?
Turning the right way?
New or old?
Has it ever run before?
Has it been sitting? How long?

It looks like you have tried most things.
I'm wondering if the coil is producing a weak spark. I've had plugs that spark good when held up to the side of the case, but they blow out when in the engine.

Good luck.

"Don't put your fingers where you won't put your face"

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04-12-2010 02:04 AM  8 years agoPost 5
jprconstruction

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Nottingham,uk

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history
been running fine,sat in workshop for 1 month,took out to fly again,pulled starter,started second pull,ran rough for 10 seconds,then stopped,after that as stated in first post.
regards
john

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04-12-2010 02:30 AM  8 years agoPost 6
Tim Ashley

rrApprentice

Saint Albans , West Virginia 25177

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ignition timing
is it poss flywheel came loose and its firing at the wrong time?

Tim Ashley AMA # 470888
Spectra G TRM 231,
wvoutlaw99@hotmail.com

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04-12-2010 02:36 AM  8 years agoPost 7
windy62

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USA

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Check the gap between the flywheel and primary coil, 2 business card thicknesses is good.

I would completely remove the kill switch, just to be sure.

Do you have any kind of "shielding" over the spark plug wiring?

Check the screen filter in the bottom of the carburetor.

windy62

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04-12-2010 02:44 AM  8 years agoPost 8
atvracer

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Transplanted to Oklahoma

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i would guess you sheared the key and spun the flywheel and your timing is off

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04-12-2010 02:54 AM  8 years agoPost 9
zorba

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Montreal, Quebec, Canada

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i would guess you sheared the key and spun the flywheel and your timing is off
I second that, If you get no pop and the engine run for 10sec then the key is broken.
Take of the pull start and the nut on the flywheel but don't take the flywheel off yet and see if the key is spun around...

Cheers

3-450's,rex500ESP,rex600G,Rex700G,Raptor60G,FreyaCW-EXII, VarioEC155, Logo20, Cessna310,CL-415,

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04-12-2010 03:51 AM  8 years agoPost 10
Peterr

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Queensland Australia

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Check the top( fan end ) bearing/seal isn't leaking ...

Don't ask how long it took me to find that was wrong with one of mine

The top, sealed , bearing was loose in the crankcase half , released most of the c/case compression ...

E ,N ,G Whiplash's;Spectra G's;Stratus;E&N Razor,Fury 55;Furion6;TSA 600N, 700N, 700G;; Be

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04-12-2010 04:15 AM  8 years agoPost 11
helicenter

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Winter Haven Fl.

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engine
All very good suggestions, how about compresion test?

Doug

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04-12-2010 05:20 AM  8 years agoPost 12
rbort

rrProfessor

Franklin, MA - USA

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To do
Replace primary coil. Use a dollar bill folded 4 fold to space out the coil gap between the coil and the rotor. Make sure to turn the rotor magnets 180 degrees away from the coil while replacing for ease of assembly/disassembly.

-=>Raja.

MA 1005 Hanson 280, 4210 flts
Spectra 27 3DMax, 3280 flts
Whiplash V1-2 Hanson 300, 1555 flts
Whiplash V2 Hanson 300, 393 flts

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04-12-2010 09:53 AM  8 years agoPost 13
shawmcky

rrElite Veteran

Isle of Wight,United Kingdom

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From your name
I am guessing you have worked with diesels,do you have any easy start around that you can see if it will fire on that?If it wont even fire on that then it probably is ignition related.

Team- unbiased opinion.K.I.S.S principle upheld here

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04-12-2010 01:22 PM  8 years agoPost 14
AceBird

rrElite Veteran

Utica, NY USA

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You said you checked compression...

So my thoughts are too much fuel. You have spark, you did the pour "gas down the cylinder trick", assuming it is not timing then it is too much fuel to fire.

To test:
Empty the tank and dry the carb out so the cylinder is dry. Now put a little fuel in the cylinder. Without any fuel being added by the carb in a couple of pulls the mixture should be able to fire even with the weakest spark. If it does your carb is stuck open supplying too much fuel regardless of where the needles are set.

Ace
What could be more fun?

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04-12-2010 01:36 PM  8 years agoPost 15
AceBird

rrElite Veteran

Utica, NY USA

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It might be easier to take the fuel supply line off rather than empty the tank.

Ace
What could be more fun?

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04-12-2010 06:11 PM  8 years agoPost 16
jprconstruction

rrApprentice

Nottingham,uk

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SOLVED
thank you all for your replies, They make very interesting reading and contain other areas of thought that may come in usefull in with future running problems.
SOLVED HERE IT COMES
I took the engine down to a mechanic i know and left it with him for the day and he reported the following.
The barrel has slight scoring all the way around(barely noticable but enough) and is allowing pressure to bypass the piston and ring.
Yes there is compression at the spark plug when you put your thumb over it,but not quite enough to get it to pop.
Good news
solved.
bad news
new head piston and ring.
thanks again for your replies regards
john
uk

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04-12-2010 08:46 PM  8 years agoPost 17
SuperSixTwo

rrVeteran

Virginia City, NV ---USA

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Its a shame that some company hasn't come out with a .10 over piston/ring combo for scratches that could be honed or bored out.

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04-13-2010 01:31 PM  8 years agoPost 18
AceBird

rrElite Veteran

Utica, NY USA

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Wouldn't that be the difference between a 231 and a 260? Doesn't it still mean a piston and a cylinder change?

Ace
What could be more fun?

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04-13-2010 05:50 PM  8 years agoPost 19
SuperSixTwo

rrVeteran

Virginia City, NV ---USA

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Wouldn't that be the difference between a 231 and a 260? Doesn't it still mean a piston and a cylinder change
Yes. I think your right. One could just change the piston and cyl-head and make the 231 a 260. An yes, an overbored cyl requires a piston. I'm thinking car stuff here....must need more coffee before i post!

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