part no./ new LB duraforce carb.
A while back I posted a message on duraforce carbs. ( see my post 'new info./LB duraforce carbs.'. The new no. is 98-7042 and the carb does come as a kit. The parts guy could not give me the old no.. What is even more disconcerting, not one person in the shop could tell me what the difference was between the new carb. and old carb., except for the fact that the new carb was in kit form. The tech. said that most of the time changes to fix a particular problem came with no explanation except replace old part with new part. Is the surging problem fixed? YES!!, most definitely! The engine runs steadily with no load, occasionally popping up 10 RPM, from 3150 to 3160 and then down as measured with a Stihl inductive tachometer. My four cycles do the same thing, so this must be within the tolerance of the measuring device, and it is not enough to be detectable by ear. Conclusion? I have no idea, since I am not any kind of expert on engine design. But I wonder, perhaps there was some design flaw in the carburator that Toro/LB fixed. That flaw may be masked by increasing the size of the jets as many have done. If any one has an LB duraforce under warranty you might try letting the shop fix the problem before going the route of increasing jet size.