125cc won’t fire
 

Am getting compression, spark and fuel, air mix is correct.
Bike still won’t start up, not even with a bump start.
Nor a fully charged after purchasing for 18 hrs at 2amps brand new 12v battery.
New plugs. Tried 4 new ones all gapped @0.7mm at spec. Also tried 0.6 and 0.8
New wire loom.
New Cdi—Sparks— plus CDai shows timing on a Green LED.
Timing chain and cam timing is set correctly.
Valves are both .05mm, to tao tao HC stock head specs.
Coil does get power to spark plug n from cdi. Kill switch has been bypassed.
It has stock starter in it. Stock Starter button switch. Stock horn.
Carb has been cleaned every inch has been double checked.
New fuel filter n gas gets to carb.
Uni Air filter, oiled n ready.
Needle clip has been changed to all 5 settings, still no starting, it’s catches for a second, never idles anymore.
Not sure what else I’ve not put down but if anyone comes up with ideas shoot em my way please. Anything helps at this point.
I did notice exhaust header gasket was not present when I purchased this bike. Just a wider OD piping. Has aftermarket exhaust, clearly showing a leak, also it always popped on de acceleration downhills.

Only 4 things to make a engine go boom.

Gas
air
compression
spark

Compression is good, it pushes against the starter motor when the battery is very low after many attempts of starting it.
HELP ME


If anyone has any further suggestions feel free to let me know. It’s been a year n the bike still won’t fire up:

What is the actual compression number ?

Try adjusting the pilot jet screw, needle position has nothing to do with starting
 

The needle clip position has nothing to do with starting. It operates from 1/4 to 3/4 throttle, then the main from 3/4 to full.

The pilot jet works in the closed (idle) to 1/4 throttle position. Put you needle clip back on the center position. Turn your pilot jet screw to 1 1/2 turns out. Try to start. Turn the screw in 1/4 turn increments (closed or open) and continue to try to start. You may have to go less than 1 1/2 or out as far as 3. Once it starts, then adjust the idle screw to get an idle in the 2000 rpm range. Then tweak the pilot jet screw up or down and watch the RPM.

Your "ideal" pilot jet screw position is 1 1/2, but 2 or so is OK and 1 1/4 is OK. If above 2 1/2, then consider getting a larger Pilot jet. If below 1 1/4, then consider a smaller Pilot jet.

Where do I go to purchase QUALITY jets?
The engine didn’t have an intake gasket on it: now it does still not firing up..
94 compression

Where to buy jets?
 

While many people claim they get "quality" jets on Ebay or Amazon, I always pay just a bit more and get them from jetsrus.com.

You can get quality no-name ones, or the actual Mikuni or Keihin jets for a bit more.

If you aren't sure of what your carb takes (it is a clone of some kind), then take measurements, photos, and your best guess of what it is a clone of (VM, PWK, PE, etc.) and send to Mike.

I have always received mine in 2 days. Also buy gaskets, etc. from them.

Post up some clear pictures of the carb and the main and pilot jets, so we can see what you're working with.

Carb
 

Here you go, I’ll find a number in a few hrs.

No pictures shown in your post...

As was said in the other 125 thread, check your valve clearances... they will get tight and make it a pain to start, not idle right, etc...

Valves are at 0.005 which is spec. I’ve relighted then over 30 times this year alone n never had the bike running since 2019, around December.

For some reason it won’t upload my
Photos from any posts.. should I log in via laptop ?

Until we can figure out whats going on with the pictures not posting here's a temporary walk around. If you reduce the file down to or below the limits before you upload it will post. Usually the file is automatically reduced when uploaded.

Attachment Key
Filetype Max Filesize
bmp 19.5 KB
doc 19.5 KB - -
gif 19.5 KB
jpe 19.5 KB
jpeg 19.5 KB
jpg 97.7 KB - -
pdf 19.5 KB - -
png 19.5 KB
psd 9.5 KB - -
txt 19.5 KB - -
zip 97.7 KB - -

You say it gets spark from the coil is it strong enough? I had coil did not make good contact with the frame because of paint and it would sputter but would not run continuously. You have gas to the carb but is it getting into the combustion chamber. I would be tempted to dribble some gas in the carb and see if it would run awhile, starting fluid can also help but be careful very explosive.

I could sand more on the paint, but I’m getting blue spark on both coils. And old one and a new one.
I have tried starting fluid. And fresh gas in tank and new filters ect, and tried dripping fluid into the spark plug hole tool. Still nothing. Got a fresh gasket set in case I do need to tear down one of these two engines, and rebuild what’s worn out.

That looks to be the stock carburetor a PZ25. I would lock the throttle all the way open. Get a spray bottle or dropper some means to get some gas back in the manifold and some gas into it and crank it over. It should run smoothly for a few seconds given you have good spark. If it fired erratically I would think something is off with the timing of the engine mechanically or the cdi signal pickup or cdi. If it ran smoothly for a few seconds I would look at another carburetor to try.

I would check that your flywheel key is intact then, as you have tried fuel in the cylinder and it still wont go, i am guessing that the spark timing is off then...