87 DT115 #1 Cylinder not firing, getting fuel has compression

[JGeiman2]

I’ve done a compression test all four are even around 115.
Tested primary and secondary coils per OHM readings, all very similar in spec.
Changed fuel pump diaphragms, cleaned carbs and reset to specs, new spark plugs.
Engine starts, idles and has a miss. It’ll run WOT but it’ll stumble and cut off at idle, even advanced on the Idle adjustment rheostat.
When I disconnect TPS, engine revs up.
I know it isn’t smart but I pulled the plug wires as it’s idling and the top cylinder doesn’t make the engine stumble but the other three do. Top plug is black (although brand new) and the others are clean but definitely getting fuel/oil.

Any help to what I should look for under the flywheel? Sheared key?

 

[99yam40]

test the input and output voltages with proper equipment of CDI as service manual should have procedures and spec if it is like the Yamahas

but to me black plug means it is burning rich, not burning at all

 

[JGeiman2]

99yam, I don’t have the CDI tester unfortunately. I’m going to pull the flywheel tomorrow and see if anything looks off.
I’ve adjust the needle on that carb out (lean for this motor) and in, both have zero effect on the condition.

 

[JGeiman2]

Voltage readings from all wires.
Secondary wires
#1 156

#2 156

#3 160

#4 160


Charge wires
Green 169

Brown 173

Battery charge
Yel/Red 6

Pulsar
Red/Gre 3.5

Red/White 2.6

White/Black 2.6

White/Green 3.4



Red 5.8

Yellow 5.9

It can jump 3/8” gap with spark.

Any ideas?

 

[JGeiman2]

Still is having issues idling. Seems to be missing sneezing. Reset idle air screw to spec and sprayed carb cleaner through it in case something was in there.

 

[99yam40]

spraying carb cleaner thru a carb does not get to all of the passages and jets.

sounds like a lean sneeze.

heated sonic bath cleaning may help, but carbs need to be completely taken apart when doing the cleaning

 

[JGeiman2]

Carbs have been completely disassembled and cleaned, that was what I did first. The cylinder is getting fuel, the new plug is wet and fairly black.

 

[JGeiman2]

I’ll take it apart again to make sure.