If I peg the throttle it will die. If I let off quick enough it returns to idle.
Sent from my iPhone using Tapatalk
I think you mean the engine will stop running completely, and if this is the case then it's my opinion that happens b/c there is not enough fuel to sustain combustion.
If there was too much fuel it would not stop running but it might sputter a bit before catching and then taking off normally.
So based on this we should concentrate on the condition of the carbs being dirty internally and restricting fuel flow. ie: Your engine is running out of fuel and is running lean.
A few suggestions:
* Replace original Tempo fuel lines, which corrode/disintegrate and contaminate your carburetors internally.
* Remove, disassemble and thoroughly clean the carburetors internally, they have Tempo Trash and years of fuel gum inside of them plugging the internal passages.
* Confirm the pop-off is repeatable and occurs at the pressure as per the shop manual specifications for your model year engine.
* While apart, confirm the high and low sped jets are the correct orifice size.
* I would recommend any carburetor rebuild should include a replacement needle and seat, these parts (specifically the needle tip) will be worn out over a period of 15~20 seasons use.
* Probably a good idea to replace the fuel selector valve, the o-rings are probably dry-rotted and unreliable, may allow air to leak inward as the fuel pump draws fuel from the tank.
It's entirely possible your green check valve in the a-pump circuit must be there yet is undocumented, especially if this was one of the early models when the a-pump was first introduced. You may recalibrate the original carbs to the earlier spec that didn't use the a-pump by installing a larger low speed pilot jet, etc. if you choose to eliminate the a-pump for some reason, such as if the internal diaphragm is damaged or other a-pump parts are broken and no longer available.
To test the a-pump you can remove the air box and watch inside the carb bore while actuating the throttle, it should squirt fuel into both of the carburetor throttle bores (not a small drizzle-drip but a healthy squirt).