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...

I have correct spark gap and the flywheel is good as is the key... not sure how to check spark timing but I’ve again had several mechanics come over and do all of those correctly..most don’t know what the start chain noise is as it comes with an adjuster that’s automatic.

I tried the stock carb. It had this no start n putter issue with the old one.
and this is what this entire problem was started with. A no start condition. (Bought a new motor and it fixed it temporarily)

I swapped to a 26 mm intake carb and it’s not running nor idling.
I believe I could get my stock carb back n try that out, but the needle is not as quality and only has 1 setting for richness.

Carb needle
 

Here’s an example of how to set the needle, yet my stock needle only has one slot to stay on.

My stock carb needle has ONE slot, this 26 mm carb has all 5, and both an AIR &FUEL mix screw, plus an idle mix screw. Total of 3 screws not 2.

I've never seen a carb with an air and a fuel screw, it's normally one or the other, plus the idle adjustment screw. I'd like to see a few more pics, if you don't mind.


1. some pics of this 3-screw carb
2. some pics of the main jet and pilot jet shown above, out of the carb to get a better idea of what style and make jets they are, along with some basic measurements in mm, including the overall length of both, the width of the main jet head and the width of the pilot jet also.
3. have you tried working from a set baseline that you can return to? From what I can tell in the above pics, it looks like a Mikuni-clone VM26/22 with a butterfly choke that is cable actuated. Knowing what size and make the main and pilot jets are is key to being able to jet it correctly.

4. How many turns OUT from seated is the fuel screw? What slot on the jet needle is the e-clip located?

Since I’ve had this carb it hasn’t ran once at idle. Not at stock factory out the box settings or any adjustments thereafter..
it is on the 3 rd rn. On the needle. Gas is in the tank n bike is indoors due to the fires.

Try spraying some carb cleaner in it and see if it'll run on that, if it does, you know it isn't a timing issue.

Won’t run on starting fluid or Fresh 91.

Here’s my Carb
Tho I didn’t Buy it from eBay.

https://www.ebay.com/itm/192106772478

It's almost definitely timing then. You could make an engine stop from an old spark plug and verify timing from there.

As posted earlier I’ve tried with 4 new spark plugs with correct timing n valve clearance. Any internal issues that can arise from using an engine for too long ...?

If the spark isn't happening at the right time, it doesn't matter if you have spark. Either the static timing is wrong, or, even if the camshaft is timed correctly to the marks on the flywheel, the marks on the flywheel are wrong for some reason.

That's why I said make a piston stop, and physically verify the timing. Not just, 'do these marks and these marks like up'? But actually checking the flywheel marks against actual crankshaft position, using a piston stop, and to get really precise, a degree wheel, but I doubt it'll be necessary, it's probably off by a ton. Did you spray the fluid directly into the combustion chamber?

You could do a leakdown test, but odds are that if it passes a compression test, the leakdown is fine. How much compression psi did you have?

Put a pencil into the spark plug hole and see the timing that way?
Psi was below 100 ��

In post 4 above you stated compression was 160-180 ,not sure how you came up with a 20lb difference with a single cylinder engine ,and now it’s 150 ? Are you just guessing at this ? I cannot remember even an original Honda horizontal ever getting near any of those numbers ,are you using the same tool every time ? The compression testers are not all accurate but they should be consistent with the same tool being used .

I agree Bruces, even with a new motor that was broken in properly I would be surprised to see anything above 135lbs and would typically expect to see about 120lbs with an accurate gauge on a little engine like this.

Has the pick up/sensor coil been tested? And if adjustable the clearance between it and the flywheel? After that it's time to verify TDC with a piston stop as previously mentioned, check timing chain and tensioner and cam position (visual confirmation that the lobes are pointed equally down) at TDC. After that tested with a timing light to see when the spark is actually happening.

At this point the carb has nothing to do with it not starting. It should run with just squirting gas or ether down the intake.

I’m gonna go and rent out another compression tester and I’m also going to get a air compressed can to check with leak down test.I’m gonna go and rent out another compression tester and I’m also going to get a air compressed can to check with leak down test

So I was going over the owners manual and maintenance manual of these hellcats and I’ve come to the conclusion that the intake valve is supposed to be 0.03 to 0.05 mm and the exhaust is supposed to be 0.05 to 0.06.
I Current intake is 0.05 as well as my exhaust valve lash.I Current intake is 0.05 as well as my exhaust valve lash
The psi was around 115. That is what I wrote down last year. Hasn’t ran since. I’m starting to think this is the original engine and NOT THE new one with less than 400 miles. This one has 1236 on it.
Pickup coil n the sensor at the flywheel have been lined up at a shop. Overcharged was usual but done by a “professional” but it’s a china bike so he’s the only “shop” that will “risk” working on it. Honda shops and Kawasaki shops won’t cuz it’s a liability.
As I was using a pos compression tester it was above 150psi. Didn’t test more than 5 times and this is the average. Now off to get a true compression tester, a spark plug tester, and a flywheel pulled and clutch holder tool.
Btw my cdi has that led light that shows when it’s sending spark.

92 psi first run.
93 the second time. 92 the 3rd time.



Could be 95. Idk if it’s increments of 5...

That’s on the low side for sure

Look were your marks are, that's reading 97. 100 is really poor compression and anything 110 or below I'd recommend a rebuild.

So anything below 110 is bad and needs to be looked into ? Timing chain removed and the rockers removed and valves removed, as well as the head, the head gasket, the piston the rod and shaft pin and clips. And leave the chain in the engine right?

if you have 97psi, it should at least pop off on a splash of fuel or ether down the carb... when i got my Roketa DB07A, it had siezed rings, and only made 67psi, but would cough on gas down the carb... i have seen engine run with 80psi like theres nothing wrong. however, after i put a new piston and ring set in my roketa, i made 170psi, and it runs like a raped ape....

for giggles, to verify, you are holding the throttle open when dong the compression test correct? you will get inaccurate readings with the throttle closed.

also, your valve lah will be fin at .05mm on both the intake and exhaust, that is still a fairly tight tolerance, .05mm is .002", most of the engines i work on (lawn mower mechanic) are .004-.013", so between double and far greater the lash. on my bike i have always set them by feel, tighten til theres no lash, then back off till you feel just a slight tick. if you cant feel the tick, its too tight.

That sounds about right ,at a minimum ,but who knows what’s up with the crank bearings ,crank and the rest of the bottom end and transmission .Yes you can buy a top end kit pretty cheap ,but the chineese components have been hit or miss ,and more often than not a miss and the engines start smoking within a few weeks of doing the job .I guess I am saying to look into another engine complete ,and since yours is a street bike I think , I wouldn’t even consider anything else .

I would believe it should cough too. Be nice if you would describe exactly what it does when you spray ether in the manifold? Does it fire at all, fire once, fire twice, 3 times, no fire at all, exactly what happens? I am not convinced this motor is getting good spark at the right time?

Same here. I'd verify the flywheel position in relation to the timing marks before replacing the top end.

The light on the CDI doesn't mean anything, pull the plug, put the cap back on it, ground the plug and crank it over.

If both the crank and cam are off because of the flywheel being in the wrong place, it could give lower compression readings.

Check the timing with the piston stop before you buy anything. Also, ether will run on an engine with that sort of compression, unless timing was way off. It could also be that your CDI doesn't have good timing at idle.

Doesn’t fire at all, coughs and sometimes spits fluid out the air filter side of carb.
Has spark but won’t ignite the vapor air mix to explode to
Idle.
Have gaskets ready for top end.
Q: what is a piston stop?
Yeah every time I brought gas directly into the spark hole and the intake, it would cough but never catch.. not
Booms.. no idling at all. I have a engine I could swap heads and all those parts on, and I have enough mula rn to
Buy a 190cc 5 speed n bolt it up. Just really tempted to take this engine into a garage and just take the top end off and examine the motor.
It has the carb gasket on, and the mechanic who came over a few times always would try starting the bike both full choke and doing all kinds of things, all
Good things like WOT starting, using the palm to choke the air intake, and using starting fluid. Never made any different sound with choke on or off, WOT, AND SPRAYING FLUID Didn’t make it fire up either. I’m starting to think I burn a valve or a ring ? Once I get home I’ll pull the flywheel cover off and again take a good readuling from it, I do know the flywheel is right and isn’t loose at all, is balanced and is the same flywheel with this bike it came with.


Main conclusion is the previous owner went HARD on this engine with out the ODOMETER running and basically trashed the motor, clicked it back up to the ODO, and ran it for 200 miles before selling it “as is” ... probably bought a motor that was predestined to die early ?

All the symptoms consistent with weak spark and/or mechanical timing issue and/or electronic timing issue. I never seen a cdi with a green light on it. I would follow Franque's advice.