Motor missing at WOT

[wili]

I have a 2001 J40JPLSIA taht is missing at WOT. Will start and idle fine but when I give it throttle it starts missing and sometimes die. I have used CDI troublshooting guide, Ohms on the coils checked out. I checked resistance on the power pack but the color codes did not match on the CDI troubleshooting guide. DVA out of all powerpacks will go up to 230 but will not go any higher. Shouldnt the voltage keep increasing with the rpm. If so what to do next?

 

[boobie]

Do a cylinder drop test on it to see if you can nail it down to one cylinder.

 

[wili]

I put a timing light on each plug and am getting the miss on all cylinders.

 

[boobie]

First guess would be a bad power pack.

 

[wili]

That was on my list but I hate just replacing parts. Is the power pack what increases the voltage as the rpms increase?

 

[wili]

Does anyone have any other suggestions to try to determine if it is in fact a power pack without just replacing?

 

[Bosunsmate]

Check the other things with the cdi checklist such as the stator

 

[wili]

Are you saying to move the stator one bolt hole in either direction? That is the only thing I see about the stator besides visually inspecting it.

So far I have checked resistance per CDI, all ok.....Checked DVA on orange wires from powerpack to coil 220-230 volts depending on RPM's.....Disconnected yellow wires still had miss.

 

[Bosunsmate]

Are you saying to move the stator one bolt hole in either direction? .

nope

 

[Bosunsmate]

how about the carbs? have you isolated it down by doing a drop test?

 

[wili]

I have rebuild carbs. I am not a mechanic but with checking each cyl with a timing light and getting a miss on each cyl I dont think a drop test will tell me anything since I have proven it is common to all cyl.

 

[racerone]

Is the S.L.O.W. system engaging ???????

 

[Bosunsmate]

I have rebuild carbs. I am not a mechanic but with checking each cyl with a timing light and getting a miss on each cyl I dont think a drop test will tell me anything since I have proven it is common to all cyl.

Are you sure that what you are seeing with the timing light is not caused from a miss from the carbs?

 

[wili]

No the slow isn't on, at least I dont believe, I am getting above 5000 RPM.

Could the carbs show black spots on the timing light?

 

[Bosunsmate]

No the slow isn't on, at least I dont believe, I am getting above 5000 RPM.

Could the carbs show black spots on the timing light?

If the engine is misfiring/lean sneezing around then, then yes in my opinion

 

[wili]

Ok, I will do a drop test when I can get it out again and let you know what I find.

 

[daselbee]

If the engine is misfiring/lean sneezing around then, then yes in my opinion

No, carbs cannot cause the ignition system to misfire, as in the spark is nonexistant or at the wrong time....no.
Consider a properly working ignition system, the flywheel is still turning, the TB is picking up pulses, the pack is triggering on those pulses, and the spark plugs are firing. Carbs cannot affect that process.

If you have no fuel at all, if you have excessive fuel, etc., then the cylinder will not fire - burn - it's fuel air charge properly but the spark will always be there at the right time, whether the fuel/air charge burns properly or not.
Again,,,,that is on a properly operating ignition system.

 

[wili]

So where should I go from here? My thought is to pull the flywheel and inspect stator, triger etc.

 

[Bosunsmate]

No, carbs cannot cause the ignition system to misfire, as in the spark is nonexistant or at the wrong time....no.
Consider a properly working ignition system, the flywheel is still turning, the TB is picking up pulses, the pack is triggering on those pulses, and the spark plugs are firing. Carbs cannot affect that process.

If you have no fuel at all, if you have excessive fuel, etc., then the cylinder will not fire - burn - it's fuel air charge properly but the spark will always be there at the right time, whether the fuel/air charge burns properly or not.
Again,,,,that is on a properly operating ignition system.

If the plugs are really wet the plug wont fire and itl show up as a dark spot on the timing light.
If another cylinder runs lean and backfires that could cause a hesitation in the CD and lead to a no spark too
Happy to be wrong but just like to make sure i am as id say the above would cause a blackspot on a timing light due to a fuel/carb issue which was what the question was

 

[daselbee]

No still don't agree. That high voltage pulse in the spark plug wire is there, no matter if the plug is wet or not. If it is WET with gas, it may not make a spark, but that HV pulse that triggers the light still occurred.