Engine fires up and idles quickly. When giving throttle engine rpm's fluctuate down then up at about 3 second intervals. Have replaced the fuel pu tube (no anti siphon valve) fuel line to bulb, the bulb, had the carbs professionally rebuilt, replaced filter, spark plugs.
When pulsation starts, pumping the bulb does not make a difference, although the bulb (original and replacement) is slow to expand; at that time and when priming originally. The only switch on the engine is the block temperature switch. Have bypassed that with no change. This engine doesn't have a computer, only a power pack, no shift switch. Fuel pumps appear good, no visible signs of problems with diaphragms, although I will replace them tomorrow but I don't hold much hope for that curing the problem. Dash temp gauges stay at 170 or less for each side. Electrical parts are expensive for this model, so hoping to identify before just replacing parts randomly.
Any assistance would be greatly appreciated.
When pulsation starts, pumping the bulb does not make a difference, although the bulb (original and replacement) is slow to expand; at that time and when priming originally. The only switch on the engine is the block temperature switch. Have bypassed that with no change. This engine doesn't have a computer, only a power pack, no shift switch. Fuel pumps appear good, no visible signs of problems with diaphragms, although I will replace them tomorrow but I don't hold much hope for that curing the problem. Dash temp gauges stay at 170 or less for each side. Electrical parts are expensive for this model, so hoping to identify before just replacing parts randomly.
Any assistance would be greatly appreciated.