ZDZ 80CC FLAT TWIN rv

[John Quinn]

Hi All ,
I'm the newest members . I've been dabbling in models since the age of 15 years, I'm 55 now
I bought 2nd hand a ZDZ 80CC FLAT TWIN RV.
I cannot get it to run , I have a spark on both cylinders , carburator is drawing fuel but will on run on choke momentarily. I've noticed it blows fuel out the carb so have looked at the rotorary reed valve and it opens just as the piston starts to rise which which I. believe is correct so as to cause a vacuum to draw fuel in - so why is fuel in a vapour blowing out ? I have compression/ unless i have some compression escaping past the rings ?
Any ideas anyone?
Thanks John Quinn

[Peter Smedley]

Could be the CDI acting up. Have an EME 120 twin that only ran on one cylinder at high revs....New CDI sorted it

[Cary Bailey]

It needs a carb kit & overhaul, sounds like your diaphragm has gone stiff plus needle valve is probably sticking causing fuel to come out the mouth of the carb.

[John Quinn]

Thanks for the reply . I've changed the carb for a new Walbro from IAD Models and the CDI unit + new plugs .
Plugs are sparking when turning over by hand .
So I'm stumped.
John

[Peter Smedley]

Have you checked the reed block. The “ petals “ might not be seating on the cage properly. It’s an easy job to lap the cage to remove any imperfections

[Peter Smedley]

Apologies, its come with rotary valve rather than the reed block. I should learn to read the OP better.

[Tony Collins 1073]

Hi John. It seems to me that the rotary valve has either been put on back to front hence blowing out of the carb or put back out of time. Also the crank seals front and rear must be in perfect condition.
This video below although being a bit long winded will explain all to you.

https://www.youtube.com/watch?v=loGsNdVLA5I

Good luck and a happy new year.
Tony.

[John Quinn]

Thanks Tony ,
I set the rotorary reed valve to open just as the piston starts to rise so as to cause a vacuum. As for the it maybe back to front - the thick part of the nylon nut faces out towards you as looking at it with the back plate off .
There is a circular recess on the back plate to accept the nylon nut standing abit proud.
I will look on that link . Thanks again John