Hi Grumpy, Thank you for your reply. The engine speed is pre-set by a hand throttle. It does not surge or vary, except under load, as is normal. Mower speed is determined by 'gear lever'/variable pulley belt drive in the range of ( park - 1 to 8). Drive belts have been replaced. The direction of the mower is selected by a mechanical shift lever for either Forward or Reverse.
The problem occurs ONLY in FORWARD gear & the engine speed is constant.
It DOES NOT occur in reverse gear.
The problem occurs whether or not the mower deck is engaged & is more noticeable the higher the speed 'gear' number is selected. This ranges 1-8.
If the problem lay with the engine as suggested, it is logical to think that the surging would occur in both directions. However, it only occurs in the forward direction. This makes me think that it may be an internal problem, but I don't want to pull the final drive apart for no apparent reason.
The motor is indeed a B&S, model 283H07 type 0197E1. It is well maintained & in good condition. Regards Kamel
