zenoah 26cc trouble after rebuild

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dc2 man

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hey all im just after getting my new head kit on the zen engine went for the same 26cc kit,piston cylinder,ring,gasket etc, i watched a video on an engine rebuild just to remind me of the whole show,so i rebuilt it but cannot start,i striped it down and everything is grand but cannot start the thing,:(
the one thing i can say is that the engine is flooding with a hell of a lot of petrol just after a few cranks,yesterday the exhaust was completly full of fuel...

strange,i cleaned it down and dryed it all up and nope just don't wana fire up,and yes plenty of spark with new plug....

all genuine parts, and iv done a few rebuilds......

help any??
 
well

Bigger the Better said:
What are your carb settings?
Do you have spark?
Click to expand...

yes bigger is better i have plenty spark and carb is set as per usual,im baffled(always something to keep a man on his toes haha)
strangest thing so it is,i put the old box type muffler(standartd) back on this rngine just to fire it up and break it in,and omg the box muffler part was full up of petrol well thanks b to god it didnt fire up or it would have been like a grenade going off:clown:

i don't know it nearly killed me to try and start it...
 
dc2 typer man28 said:
yes bigger is better i have plenty spark and carb is set as per usual,im baffled(always something to keep a man on his toes haha)
strangest thing so it is,i put the old box type muffler(standartd) back on this rngine just to fire it up and break it in,and omg the box muffler part was full up of petrol well thanks b to god it didnt fire up or it would have been like a grenade going off:clown:

i don't know it nearly killed me to try and start it...
Click to expand...


Take off the card.
tear it down and clean the parst whit carburetor cleaner.
i guess ther is sand in it.
 
I just went through the same thing on my Redcat. I got a complete headkit in a trade, stuffed crank etc... I busted my pull start string as I tried everything to get it running.... I replaced the original stuff and it fired second pull. It was a race ported kit from ddm that I got in a trade. It seemed to not have good compression though.... Did you get the dot on the piston facing the exhaust?
 
hey pipous

pipeous said:
I just went through the same thing on my Redcat. I got a complete headkit in a trade, stuffed crank etc... I busted my pull start string as I tried everything to get it running.... I replaced the original stuff and it fired second pull. It was a race ported kit from ddm that I got in a trade. It seemed to not have good compression though.... Did you get the dot on the piston facing the exhaust?
Click to expand...

are you serious,god it is strange man isnt it.!!!
yeah man i have tryed everything,i literaly tryed everything,was kinda looking forward to starting it after the rebuild just to watch it tick over running in(out of the car) am yeah i cleaned the whole carb,choke is not on (just for a minute trying to get fuel in the system,arrow is facing exhaust on the piston....
brand new kit,cleaned everything thoroughly just to make sure i even watched fast edys engine rebuilding video to make sure i would memorise everything.
im BAFFLED BY THIS ENGINE !! and iv rebuilt a few......
 
Its possible you may have received a bad ring (out of round) its happened to me a couple times and it will do exactly what your describing another thing it could be with the symptoms you describe is the seat in the carb, if it goes bad or is stuck fuel will poor out of the carb with every pull till the lower end fills up and pushes it through the exhaust.
 
yeah it could be the case of a dodgey piston ring,but i did check it well and it looked pretty tight and even,although maybe it wouldnt be possible for the naked eye to spot such miniscual imperfections.
i checked the carb aswell and looks fine..
 
pulse port is likely blocked. the pulse port is the Small hole coming from the bottom of the carb manifold on the cylinder. it goes thru the carb manifold to the carb and opperates the diaphram that pumps gas from the carb.

If the pulse port is blocked (typically on a rebuild this ends up being the gasket pulse port hole between the manifold and the cylinder not being open, or possibly the gasket being upside down blocking the pulse port completely), which causes the gas to freely flow flooding out the motor. this is the first thing i would check is the pulse port is open and unblocked. if it is fine, then swap out the carb and see how it goes.

bad ring wouldnt cause the motor to flood unless you flipped the choke on and never flipped it off cuz you never got the initial Pop you expected. but a simple test to check for a bad ring, is to pour about 2 tablespoons of straight 2 cycle oil into the cylinder. move teh motor around to coat the inside of the cylinder as well as the piston and ring. then try to start. if it fires up and runs, then that says you have a compression issue, and a bad ring is likely, especially on a new topend.

hth
 
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good advice there timmah god maybe it is that pulse port,is that on the isolator block aka (intake manifold)?i havnt had a chance to check it to start sinse but i must now first chance,keep the good advice coming lol
cheers!
ill let ye know if she fires up in the meantime
 
yes the small hole thru the bottom of the manifold. sometimes the hole is punched in the new gasket on one side, you may have yours hole up, not down, or maybe the punch is still there, blocking the hole. also check the carb side to be sure that pulse port isnt plugged/blocked.
 
dc2 typer man28 said:
hey all im just after getting my new head kit on the zen engine went for the same 26cc kit,piston cylinder,ring,gasket etc, i watched a video on an engine rebuild just to remind me of the whole show,so i rebuilt it but cannot start,i striped it down and everything is grand but cannot start the thing,:(
the one thing i can say is that the engine is flooding with a hell of a lot of petrol just after a few cranks,yesterday the exhaust was completely full of fuel...

strange,i cleaned it down and dried it all up and nope just don't wanna fire up,and yes plenty of spark with new plug....

all genuine parts, and iv done a few rebuilds......

help any??
Click to expand...
Did you get it straightened out?

...If not, I was thinking maybe the gap between the coil and the flywheel was set too high? (I use a business card to set the distance, approx .015" or .381mm) The reason I was thinking this is because, you can have good spark when the plug is out of the head, but when the plug is In the head, the compression can "Blow-out" the spark. It is not as common on our small 2-strokes, but it happens alot on bigger motors, but compression and pipes whether tuned or not, have a big affect on how a 2-stroke operates.

This a true story that I would happily swear my life on...

I know this sounds a little strange... But I was playing around with a flooded (snowmobile) engine... The motor was flooded like crazy, (At the time I didn't know it was flooded) I pulled the pull rope, time and time again, but it wouldn't fire... So I removed the plugs and thought I would check for spark ...I grounded the plugs on the heads. (As anyone would do to check for spark) Then I yanked the pull rope again.

On the first pull, it shot gas/petrol about 3 feet/1 meter into the air. On the second pull, the engine Fired!!!!!! It STARTED! The plugs were lying on the heads!

...I could see the spark coming from the spark plugs and igniting the fuel while the "spray" of fuel was being sucked backed down into the combustion chamber!!! (Surprising to me at the time, there was not a big flame coming from the spark plug holes, just a line of fire travailing into the motor) The engine revved uncontrollably for about 10-15 seconds then I hit the kill switch.

So after that, I realized carb tuning is not that important to get the engine to run, but it is important to get it to run properly.

I would drain the fuel tank and drain the fuel lines. Then drop a few drops of fuel (about a thimbleful) into the spark plug hole and give the pull rope a tug. If it fires, then you know it is carb problems. If it does NOT fire, start checking ignition or compression...



Let us know,
Trip..
Just my 2 cents, but it may only be worth half of what I said...
 
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I've had a similar experience. Sean from O'neils helped me out with a simple check. I rebuild my Zen 26 into a 30.5 race ported kit I bought from them. Tried starting it and nothing. My tricep was so sore after 30 minutes of trying. I e-mailed Sean and he called me right back at home in Canada! Gave me a little tip that works very well.

Remove the carb and try starting it. The engine should fire up at a high throttle to remove the excess gas at the bottom. When you do this make sure nothing is in the way of the drivetrain and the vehicle is up on a stand. Once it fires shut it off so have you finger close to the kill switch.
Put the carb back on and it should be fine.

Iv'e used this method to also start my airboat in cold temps.

Let us know how it goes.
 
hi there, mate if you have fuel comming out the exhuast gotto be needle and seat .. to test it take it off and have fuel tank above the carb and see if fuel leaks out..the only other possibility is a small hole in the diaphram.. if the vac port was blocked or on wrong you would not get any pulse therefore no fuel..hope this helps
 
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I am new to the RC world, i have a Piper Cub that i am trying to get running. I set distributor contacts with business card, and spark plug seems to have good spark but it will not fire at all or even try when i put fuel straight in the cylinder. I don't understand why it will not run
 
dc2 man said:
hey pipous



are you serious,god it is strange man isnt it.!!!
yeah man i have tryed everything,i literaly tryed everything,was kinda looking forward to starting it after the rebuild just to watch it tick over running in(out of the car) am yeah i cleaned the whole carb,choke is not on (just for a minute trying to get fuel in the system,arrow is facing exhaust on the piston....
brand new kit,cleaned everything thoroughly just to make sure i even watched fast edys engine rebuilding video to make sure i would memorise everything.
im BAFFLED BY THIS ENGINE !! and iv rebuilt a few......
Click to expand...
Omg! I got the same problem now mate! Did you solve the problem? Tks
 
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