Engine wont start! Seems like a mystery.

[EnergyInducti...]

Got a 1986 Honda CG with CDI outside, It was given to me as a non runner.
First thing I did was change the petrol, Would not start.
New spark plug, Would not start.
Checked for irregular sparking and all was fine with a crisp spark
Checked fuel lines and got covered in the stuff, Yep thats fine.
had the carb cleaned professionally and it's still not running.
Engine requires a fairly strong kick for the upward strokes, yet smooth during other cycles and I've tried the thumb over spark plug hole and it blows it off easily.
One thing seems abnormal, And that's that petrol seems to fly out the back of the carb.
I've had it fire about 5 times out of 100 kicks, And it sounds like it fires down the exhaust, Not the engine.
HELP! =(
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[Frost]

Sounds like it could be a lack of compression, or potentially an issue with top end timings.
Before you open up that bag of worms it would be best to make sure your doing everything correctly:

Take the spark plug out and with the ignition turned off give the starter 10 quick kicks, should turn over very easily.
After checking things like the choke is on full and the throttle closed put the spark plug back in.
Gently push the kick start down until it gets though to move (compression from the cylinder moving up). Slowly but firmly push it passed this point and stop just as it becomes easy to move. This will have the cylinder filled with compressed air to help get the piston moving down again.
Give it a long kick right to the bottom of the stroke. Don't stamp on in, push throughout the stroke getting faster towards the bottom.

[Alexio]

I would have it properly compression tested. After that I would make sure the valve clearances are correct and try to hill start it. I hope the oil is ok too.
____________________
will never give up his CG. I look at my fuel gauge more as a progress bar than a fuel gauge.
G: With my GSXR I do often effectively use it as a scooter with a clutch in town.
ms51ves3: why does it need 500 miles? Are you teaching it how to be a piston?

[temeluchus]

[EnergyInducti...]

[DeeTee]

check your valve clearances, sounds like the inlet valve isnt sealing, if the clearances are ok you will have too look deeper at these valves and do a compression test.

[EnergyInducti...]

[temeluchus]

try this

https://honda-cg.ifrance.com/Honda-CG-125-1976-1991.pdf

Also check the valves like DeeTee says.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[Alexio]

[EnergyInducti...]

Right, My CG engine is out of the frame and upstairs with a waterproof sheet underneath it.
Valve clearances were about 0.04mm for both inlet and exhaust, set them back to 0.08mm
HOWEVER... If there is ONE thing I have learnt... It's never trust a previous owner.
The carbs HAVENT been done... Varnished inside, There is carbon where the air filter connects (My friend mentioned it caught fire last time he had it running)
It doesnt look like you can change the float height... but its working fine
Could not see through the main jet, OR the pilot jet so I've blown through them both hard and you can see through them now.
Going to wait till I get some carb cleaner and new screws till I put it all back together.
Anyone know where I can get the screws that hold the carb together?
Also, Would it be worth me taking the valves out and replacing the seals and head gasket? (Head gasket because I obv need to take the head off to get to valves) =P
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[EnergyInducti...]

VERY silly question, And I feel like a fool for asking this, But in my own little world, I kept thinking that the CG was CDI... but one thing dawned on me as I researched into these more and more...
These bikes didnt have CDI back in 1986 did they..... >.>
I wondered why I couldnt find a replacement CDI...
And after that embarassing moment, Could the contact breakers be the reason it's not starting?
I was getting a nice regular spark before... but I'm starting to doubt everything I once believed was true about the bike...
When I get home I'm gunna get out the feeler gauges and check *Sigh* Wish me luck =)
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[DeeTee]

But your original post said ...
"New spark plug, Would not start.
Checked for irregular sparking and all was fine with a crisp spark"
So wre not likely to be suspecting that ere we?
and anyhow this would not cause fuel to "fly" out the back of the carb. More to do with sticking valves, incorrect clearances, burned seats...its a valve issue i think, youve done the easy thing ie re-set the clearance, cross your fingers it cures it.

[Ariel Badger]

It was flooding, that is my fuel was coming out both ends and banging in the pipe. Clean the carb and try again, if that does not work try a new new plug.
____________________
Bikers make great organ donors, get 115 on your licence today.

[Robby]

Fix what you know to be wrong first. So a clean carb is the start. This can also explain fuel leaking out of it.

If fuel was being forced back out of it as a mist, you'd have compression going back through your carb. This would make me wonder if the cam shaft has been out and not timed properly (or out by 180 degress) when it went back, but checking that is a fair way down the road.

I don't know if the CG had CDI in '86, but it definately existed. My '79 or '80 CB250 has a CDI. If you can't see a points cover, it probably does.

For screws, your local hardware store should have some. Take one of the old ones for reference. The easiest way to be sure it's the correct thread size and pitch is to roll the threads of the old screw against a new one. If they mesh, it's the right size.

[st3v3]

[Robby]

Most carbs have 4 small screws holding the float bowl on. These are made of that special Japanese cheese-based metal, cheesenseize. Always worth replacing with stainless allen screws, as long as you screw then in carefully and don't wreck the threads in the carb body.

I assume this is a normal slide carb and not a CV, so the top may be held on with a couple more cheesensieze screws. It may be a screw-on top, but I've only seen that on two strokes.

[temeluchus]

A modelling shop is a good source for the m4, m5 bolts u need for carbies.
____________________
Some shite cruiser. Now with guns and FREEDOM!

[EnergyInducti...]

I've taken the head off and it smelt burnt... thats the only way I can explain it.
Cylinder head was BLACK... but nothing that a scouring pad and furniture polish couldnt fix =P
The exhaust valve looks fine and normal, But the inlet valve worries me. It's several shades of grey... Like the mottled grey of the cooling fins on an old engine...
It looks like it's seating fine either way, So if it aint broke, I'm not going to bother tinkering =P
Looked inside the rotor, And yes, I have contact breakers. It looked like something was stuck on them when opened which seems strange, Something sticky like oil...
Any idea how to get the damn bolt off? It keeps spinning... I have no access to an impact ratched either... =(
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[EnergyInducti...]

I think what i'm gunna do s order some new gaskets and put the bike back together, run a compression test, and take it from there. Sound right?
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[Alexio]

What's to stop you from doing a compression test now anyway? Do the gaskets need to be replaced?
____________________
will never give up his CG. I look at my fuel gauge more as a progress bar than a fuel gauge.
G: With my GSXR I do often effectively use it as a scooter with a clutch in town.
ms51ves3: why does it need 500 miles? Are you teaching it how to be a piston?

[EnergyInducti...]

When i took the cylinder head off, the gasket was burnt to a crisp and torn in 2. And there's no point puttin it back together without a gasket lol
____________________
Riding: Yamaha RXS100
Aiming for : RD350 + Test
Dream bike: Suzi RG500 Gamma

[Alexio]

Then yes! lol, your plan is a good one.
____________________
will never give up his CG. I look at my fuel gauge more as a progress bar than a fuel gauge.
G: With my GSXR I do often effectively use it as a scooter with a clutch in town.
ms51ves3: why does it need 500 miles? Are you teaching it how to be a piston?

[temeluchus]