Is my Engine toast?

[Rooz12]

Hi,

I have a keeway superlight 125 and I just replaced my engine today.

the old one has issues with the gearbox (posted a thread about it on this forum).

The new engine works fine until I twist the throttle and it starts making some strange noises and it dies/cuts off!

If I leave it running without twisting the throttle, it works just fine and it runs smoothly.


I thought the the issue was due to the fact that the engine wasn't getting enough air. So I disconnected the carb and tried again and same thing happens.

I started looking into the carb's air intake mouth (where the carb connects to the air filter housing) and I when I twist the throttle, I see sparks! not sure if this is even normal.

I've recorded the whole thing so you can see: https://streamable.com/dmhsph


in the video, you can clearly hear the difference between when I twist the throttle and when I'm not. you can also see the sparks in the carb!


Is my engine toast?

[xX-Alex-Xx]

Not sparks, flame.

Could be a few things.... Inlet valves not sealing would be my guess.
____________________
DILLIGAF

[WD Forte]

That's called popping back round here
the engine sounds otherwise ok

could be the afore mentioned leaky valve
too lean a mixture or ill set ignition timing

just needs more examination and testing

what year bike was the engine from?
if was from a later efi one the ignition pulser may differ
____________________
bikers smell of wee

[Rooz12]

[stinkwheel]

Two things I'd check with an engine spitting back like that are that the inlet valve clearance is ok. If it's too tight, it could be holding the valve open. Also that the alternator rotor hasn't spun up which would play merry hell with the ignition timing.

Or the valve timing could be out.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Rooz12]

[WD Forte]

I hinted to this in a previous thread
the carbed bike will use a common or garden pulser
whereas efi bikes often use a more complex toothed wheel
with say a missing tooth
these may send all manner of pulses to an older CDI system.

I'd whip the stator cover off and see if I could fit fit the old/simple stator & pulser to the newer efi engine.
____________________
bikers smell of wee

[xX-Alex-Xx]

I assume your throttle body on the old one has a TPS as well? Does this carry over to the carb?
____________________
DILLIGAF

[Rooz12]

[stinkwheel]

[xX-Alex-Xx]

TPS: throttle position sensor. Sits on the side of the butterfly and measures how far open you've got the throttle and sends that signal to the ECU to adjust the fuelling. These typically aren't on carbs as they're not needed on those.

You sure you've got no loose connectors hanging down?

As WD Forte has said, you typically can't swap a throttle body for a carb or vice versa and expect to work with no other mods.
____________________
DILLIGAF

[Rooz12]

[Rooz12]

[Mysteriass]

You may need to swap the flywheel and the stator. The flywheel itself might have timers.

[Rooz12]

[Rooz12]

[Rooz12]

[Rooz12]

Just did a quick search on Google and someone else asked the same question on another forum and the answers indicated that the wires (black/white) are reversed!


Although this was for a different bike. not my bike.

I have different colours wires.

[stinkwheel]

The ignition timing is set by prescisely when a step on the outside of the rotor passes the pickup coil in the stator cover (the black rectangular bit at the top left of your pictures).

Usually a fuel injected motor has multiple steps to signal detailed information to the ECU which works out when it wants the spark and fuel pulses to happen while a carbed one usually has a single step which just sends a signal to spark once per engine rotation.

Using an FI stator and rotor on a carbed bike will be sending spurious signals to the ignition. It's probably producing multiple sparks at varying points of the engine cycle (which fits with all the previous posters suggesting ignition timing being out) instead of a single spark just before top dead centre.

I'm actually amazed it's running at all.

If you are lucky. Swapping the stator AND rotor will work. That's assuming that the key position on the crank (which locates where that step sits in relation to the crank position) is identical on both engines.

Popping a rotor off when you're already in there isn't a big job if you have the correct tool. Like less than 5 minutes when the cover is already off. This is assuming the replacement one has the same keying.

If you post where you are, someone might be able to pop over and help you with it. While there are a lot of dicks on BCF, a lot of them are surprisingly helpful dicks. I have a rotor pulling tool, this is assuming the flywheel has the same thread size as they use on Hondas and yamahas (which is fairly likely, because the Chinese copy things, not make up new things on the whole).
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Rooz12]

[Rooz12]

[stinkwheel]

[pbt]

The stator and Flywheel are both completely different between the carbed and efi models. You need to swap both.

EFI
https://shop.motogb.co.uk/parts-catalogues/25400/KEEWAY%20Superlight%20Std%20EFI%20Euro%204

Carbed
https://shop.motogb.co.uk/parts-catalogues/17507/KEEWAY%20Superlight%20125%20Ltd%20Euro%203

[Rooz12]

[Rooz12]