180 out with waste spark?

[EMira]

Is it possible to have the camshaft 180 degrees out while having a single coil? I have a fresh rebuild engine that may have the cam 180 out. I never had it running and it has mikes xs PMA with Xcharge ingition and new VM34 carbs. All new and new ran together. While cranking i have a back fire though the carbs.

 

[Jim]

Is it possible to have the camshaft 180 degrees out while having a single coil?

Depends on what you mean by 180° out.
180° measured at the camshaft is OK because like you said, it's a wasted spark.
If you mean 180° at the crankshaft, that would put the pistons at BDC when it fires.

Do a site search for Xcharge ignition and you'll find most folk consider 'em junk. Worse than junk actually....

 

[EMira]

At TDC on the compression stroke the pin on my ignition rod in at 6 o clock

 

[Jim]

At TDC on the compression stroke the pin on my ignition rod in at 6 o clock

So the cam is 180° out.... with a wasted spark ignition system it should still run just fine.

 

[EMira]

Depends on what you mean by 180° out.
180° measured at the camshaft is OK because like you said, it's a wasted spark.
If you mean 180° at the crankshaft, that would put the pistons at BDC when it fires.

Do a site search for Xcharge ignition and you'll find most folk consider 'em junk. Worse than junk actually....

So ya. The timing light shows it firing 180 out. For give my ignorance, but how do i fix this?

 

[Jim]

No need to fix it. If it's a dual output coil, both cylinders will fire every 360° of crank rotation. You could tear the motor back apart and rotate the cam 180°... and both cylinders will still fire every 360° One up top on compression and the other up top on valve overlap.... the wasted spark.

In other words, that won't prevent it running.

 

[Jim]

... unless you mean the crankshaft is 180° out? Pistons on the bottom when it fires?

 

[EMira]

How could the crankshaft be 180 out? My TDC mark on my crank case is 180 of the mark with my timing light

 

[Jim]

Put some pics up so we can see where you're at?

 

[EMira]

So when i crank it with a timing light it just back fires through the carbs ( no choke ), when i put the chokes on i get no back firing. The timing light shows my TDC mark on the Crank 180 off from my side cover mark.

 

[Jim]

The timing light shows my TDC mark on the Crank 180 off from my side cover mark.

I'm even more confused now. You say it's 180° out, yet the pic shows both marks lined up...

 

[Jim]

Are you saying that when the timing light fires the mark on the rotor is straight up?

 

[EMira]

Yes

 

[Jim]

Have you double checked that the pistons are at TDC when the timing marks line up at the bottom?

 

[EMira]

When the timing mark is at the bottom the piston is at TDC just after the intake valve closes.

 

[Jan_P]

Cam one tooth off ??
Is it just me or is that 6 or 5.30

 

[Jim]

When the timing mark is at the bottom the piston is at TDC just after the intake valve closes.

And with it as you describe... TDC and mark down, where is the cam pin?
Up, down or horizontal?

 

[EMira]

Cam one tooth off ??
Is it just me or is that 6 or 5.30

View attachment 242295

New photo at TDC as described. It’s 6

 

[EMira]

And with it as you describe... TDC and mark down, where is the cam pin?
Up, down or horizontal?

 

[EMira]

And with it as you describe... TDC and mark down, where is the cam pin?
Up, down or horizontal?