1988 Force 50 507T8B high speed miss. Tried everything.

[WalleyedNJ]

I have a new to me 1988 Force 50, model 507T8B, with a high speed miss I can't diagnose.

This is what I've done so far:

Verified connectors all all stator/trigger wires are good
Verified stator and trigger resistance and voltage output with a DVA, all within normal range.
Set and verified timing (28 degrees BTDC at WOT)
Cleaned carburetor
Rebuilt fuel pump
replace all fuel lines and new primer bulb.
Fresh gas/oil mixture
new plugs
spark jumps a 7/16" gap with good color.
compression is 125 psi on both cylinders

removing stator charging wires from rectifier had no effect.

Running engine in garbage can:

Idle set at 1000rpm. Engine idles smoothly, no issues.

Slowing rev it up and it starts to misfire around 2600-2800 rpm.

I'm running out of things to check and I don't want to just start swapping parts.

Only slight oddity is the coil/cdi pack for cylinder 1 is the old style, cylinder 2 is the new style.

What's my next step?

Thanks,

Jim

 

[WinnerCougar74]

Double/triple check your fuel pump. I had a stumble that started at 2500rpms and a new fuel pump diaphragm fixed it. They seems to go bad very easily. Maybe the one you put in was bad.

 

[jerryjerry05]

Any blowback from the carb?
Check the reeds?

 

[WalleyedNJ]

No blowback, no spitting, throttle plate parallel at WOT.

I have not pulled the reed assembly, I guess that's next.

 

[The Force power]

I have a new to me 1988 Force 50, model 507T8B, with a high speed miss I can't diagnose.

This is what I've done so far:

Verified connectors all all stator/trigger wires are good
Verified stator and trigger resistance and voltage output with a DVA, all within normal range.
Set and verified timing (28 degrees BTDC at WOT)
Cleaned carburetor
Rebuilt fuel pump
replace all fuel lines and new primer bulb.
Fresh gas/oil mixture
new plugs
spark jumps a 7/16" gap with good color.
compression is 125 psi on both cylinders

removing stator charging wires from rectifier had no effect.

Running engine in garbage can:

Idle set at 1000rpm. Engine idles smoothly, no issues.

Slowing rev it up and it starts to misfire around 2600-2800 rpm.

I'm running out of things to check and I don't want to just start swapping parts.

Only slight oddity is the coil/cdi pack for cylinder 1 is the old style, cylinder 2 is the new style.

What's my next step?

Thanks,

Jim

Here's a link that will assist you with diagnosing the ignition;

https://www.outboardignition.com/page8.asp

 

[WalleyedNJ]

Here's a link that will assist you with diagnosing the ignition;

https://www.outboardignition.com/page8.asp

I've walked thru everything in there, one thing I haven't done is pull the flywheel and visually inspected the stator.

 

[The Force power]

Stators can test good, but are not

 

[Redbarron%%]

Lots of surprises when the flywheel comes off.

 

[jerryjerry05]

They sell a "snake camera" for the new smart phones.
My Android, I bought a camera for 11$.and it works great.

Just hook it up and look at the reeds.
You can remove the carb or not??
Make sure you get the one with the firm/stiff cable.

 

[WalleyedNJ]

Yes, I can remove the carb, I've already had it off. I did a cursory look at the reeds at that time, but I need to inspect them further.