Fouling Plugs ring issue or compression issue?

[Moparfiend]

Ok this is opposite of a 426 issue in that its for my 50cc scooter. But hey it’s an engine right?

Not apparently burning oil in that no smoke in the exhaust is noticeable.

Issue.
Keep fouling my plug. I have a single 28mm cv carb that I’ve adjusted and think isn’t too rich (like me). Still fouling.

Did a compression check and with a 12:1 cr should have about 190psi but was only getting 140psi. Added a little oil to the cylinder and then got 190psi.

Haven’t check valve lash yet.

Question
If the compression came back after oil was added does that definitively confirm ring/cylinder issue or could it still possibly be a valve lash issue?

Thanks
MF

 

[GTX JOHN]

It sound like it is a ring issue.
Very simple to rering and hone the 50cc.
Usually does not require an over bore but check
cylinder to be sure.
We use several at the Drag Strip.
Be sure Oil Injection is not going overboard.

 

[Mick56]

Is it a 4 or 2 cycle?

 

[Moparfiend]

4 cycle no oil injection

 

[RemCharger]

Try a hotter plug?

 

[Moparfiend]

Try a hotter plug?

I did! I went one heat range up then two and it fouls fast like right away after 10 mins of riding.

 

[Kern Dog]

Anytime the cranking compression jumps after squirting some oil in the cylinder, it means that the rings in that cylinder are not sealing. The oil acts as a temporary sealant between the rings and cylinder walls.

 

[Moparfiend]

Anytime the cranking compression jumps after squirting some oil in the cylinder, it means that the rings in that cylinder are not sealing. The oil acts as a temporary sealant between the rings and cylinder walls.

Yeah that’s what I thought too. Looks like I’ll be pulling the motor and buying some rings and a piston. Good news I can do it in my kitchen lol.

 

[Geoff 2]

Check the coil, etc. Weak ign system [ like a points ign ] will also foul plugs.

 

[Wietse]

That carb is the original one? 28mm sounds a little big for a 50cc.

 

[Mick56]

Does it use any oil? If not, might just be running too rich.

 

[WileERobby]

What does the spark plug look like ? Could be oil, or carbon, fouled. Also, the ignition ^^^ as stated a possibility.

 

[Don Frelier]

I think 140 psi would be fine to run well.
Are you sure the crankcase is getting vented properly?

 

[super-bee_ski]

Wrong plug?

 

[Moparfiend]

Wrong plug?n

Wish it was that would be a simple fix.

 

[kiwigtx]

As we say down under....give it a bit more jandal.

Or....a bit more weight on the loafers.

 

[Moparfiend]

As we say down under....give it a bit more jandal.

Or....a bit more weight on the loafers.

Lol no clue here. Bad rings I don’t think any jandal will help what ever that is. Can you smoke it? Maybe it’ll help me lol.

 

[RemCharger]

I don't have a proper decoder.. but I'm guessing he means put more load on the engine??

Or ya,, some sort of weed to take the load off.

 

[Moparfiend]

This was after about a 25 minute run around town. Thought I’d throw it up for you guys to look at maybe someone’s better at reading a plug than me not sure if you can tell if it’s carbon fuel or oil etc. I am not burning oil and at 140 PSI like others have said should be fail to run. And in fact it runs good intil it fouls. I’ve leaned the carb out so maybe a crappy ignition? Other than looking at the spark is there a way to quantify the quality of ignition?
Many thanks…
PS the speckles are dust from sitting out…

Edited: After looking at my plug more carefully I think its a rich condition and not oil blowby. Its dry and sooty looking thats why I am thinking this. This was a brand new plug.

 

[JDmac72chrgr]

check voltage into coil THEN voltage out of coil:
check plug wire, could be "jumping" voltage to ground instead full volts to plug