Cpi Popcorn 50cc 2t acting weird with 70cc kit

Hi Folks

I have a 2004 Cpi popcorn with a minarelli style engine.
I bought it in running condition with a original 50cc cylinder, i never ran it much cuz it was simply to slow to be any fun.
I took the engine out and purchased a naraku 70cc kit. put it all back together, use the original carb but with a bigger yet. Started and ran fine, but if u tried to ride it, after 20 meters or so it started dieing out, acting like it didnt get enough gas.

I thought well, i better get a bigger carb, so i got a 17mm carb and a jet kit. Tried jet sizes from 85 up to 105. 105 is still in it now.
if u start it on the centerstand and rev it out, it sounds good, running a little rich at first but if u hold the revs up it starts to clear up. However, if u try to ride it, its the same as with the orgiginal carb, you get like 20 meters and it acts like its running out of fuel. I can see in the fuel line that it actually has fuel coming, however its hard to see this while im riding, but i do believe the fuel flow is decent.

Also after riding it for 20 meters, the idle goes up, just like its starving for fuel and if u try to throttle it it wont rev at all. i let it idle like this with a high idle for a bit and like with a snap with ur fingers the idle suddenly went down again and its back to running rich, i tried to ride it again, but same thing as before i got like 20 meters and same thing happened again.

Another weird thing i noticed, when it acts like its starving for fuel, i can turn the ignition key off but the scooter will still run and to stop it i had to choke the carb with my hand.

Can this be a cdi problem? i dont know if a cdi box can make it act like its running out of fuel?
is a 105 mainjet still too small? what confuses me is that it seems to run perfect while on the centerstand.

im pretty certain it doesnt get any false air, i tried spraying it here and there and i dont notice any diffrence.

i also notice after its been running, it seems to spit back a bit if fuel down the airfilter neck, seems a bit odd to me but maybe its normal on these bigger carbs and cylinders?

A thought that has crossed my mind, but im 95% sure i didnt do this, is install the piston the wrong way. However im starting to doubt myself, so im wondering if i should take the head back off and look. Would that cause these symptoms?

Thanks in advance for any help and tips, im getting tired of fiddling with this blindly and it seems nothing i try really helps.

This is the specs of my scooter now;
stock exhaust
stock airbox but plenty of holes drilled in the plastic
17mm carb with 105 main jet
naraku 70cc cylinder
stock cdi box
ignition system is untouched/original

 

I'd say main jet is way to big, a 125cc only has 82.5 in a 20.5mm carb. check plug colour and start checking everything again.

 

Thank you for ur answer.

I checked the sparkplug, it actually looks pretty good, brownish, however it also wet.
I now tested several new sparkplugs, the spark is very weak in my opinion, but its a blue spark.
the spark also seems to move around on the electrode quite a bit.
I see it has a pickup on the flywheel, the gap between the flywheel and pickup seems pretty huge to me, but idk the specs.
since it has a pickup, does it still have points or is it fully electronic ignition? i tried to look in the holes of the flywheel but i cant see points anywhere, the holes in the flywheel is rather small tho, so not sure if their hiding in there somewhere.

Im still confused by this since it really acts like its starving of fuel, but since the cylinder and sparkplug appears to be wet, im guessing it must be a spark issue.

very weird it doesnt just bog down tho from all the gas?

THanks again for ur help

 

I been doing some more work and troubleshooting now. Adjusted the pickup on the flywheel to about 0.3mm, didnt really make any diffrence, spark still seems very weak. Checked the sparkplugwire and its all good.
Also checked to make sure i indeed set the piston in the cylinder the right way, and it is correct.

I cant see any leaking around the crankshaftseals either so i doubt thats a problem.

How good/big spark is it on these kinda scooters? even on lawnmowers and such theres better spark than on my scooter.

Also the fact that it did run with the ignition key off makes me suspect something electric.

im not sure the cdi box would cause weak spark or other problems that im experiencing, but im starting to lean towards maybe exactly that.

Hope some of you have some suggestions, i hate just starting to throw parts at it and just hope something will solve the problem.

THanks again

 

105 main jet is way too big.
The Naraku 70 kit is not much better than the standard 50 setup.
The air gap on the pick-up to flywheel should be 1mm.
Check the float height on the carb and drop the jet size
Get an un-restricted cdi
Lighter rollers