This thread is to record my experience and findings with regard to modifying a small industrial V-twin for aircraft use as inspired by this thread a few months ago.
The first problem is that the engine was back ordered and when I called I was told that they would not have another shipment for nearly 2 months. I canceled the order at that time, or so I thought. About a month later when I left the house I found a box setting in the driveway. It was a HF engine. The delivery driver did not ring the door bell and there was no signature required. The next day I received postcards from HF notifying me that the order had been canceled and a second saying that the order had been on back order for over 30 days and per UCC I could cancel the order. I called HF and was informed that my order had in fact been canceled. My bank account had not yet been drafted so I decided to wait and see what happened. Long story short my bank account did get drafted and I was stuck with the HF engine. I decided to evaluate it as planned rather than continue to try to get return the engine. They did honor discount coupon number. I don't know if they would if one were to buy from a store.
A few days ago I found time to unbox the engine and start examining it. Here is what I've found in no particular order:
First impression is that the fit and finish is actually quite good. If it had a Honda of a B+S sticker on it rather than Predator it would be believable.
Weight on my digital scale was 95 pounds with the air cleaner, muffler, and fan shroud removed. The removed parts weigh :
Air cleaner = 3 pounds
Shroud = 1.5 pounds
Muffler = 9 3/4 pounds
The engine can use 10% ethanol fuel but not E85. It comes with 2 sets of main jets for high altitude. They are different side to side due to the cheap intake/exhaust design, which is common to most of these V-twin industrial engines.
The oil cooler is plumbed with hose that uses spring type clamps. The oil filter base is integral with the case, unlike the Honda GX690 which is a separate part.
Carb mixture adjustments are sealed - as would be expected for an EPA certified engine. But at least they are there.
The stamped steel rockers look less than substantial. But then the valves are small and the single valve spring is also pretty small. The wear surface area on the shaft is probably a source of excessive wear, but a fix would be simple. The valve lash was adjusted properly.
The crankshaft PTO end appeared to be well machined with good finish and no tooling marks. A manual check of the end play seemed excessive and measured at .016" - a lot less than I had thought. It was still enough to prompt me to remove the case cover to look inside before running the engine. The gasket measured .020 thick so the end play could be adjusted by surfacing the thrust surface of the crankcase cover (both the cam and crank) as needed and assembling with no gasket and anaerobic sealant. I didn't pull the crank but it appears that the thrust is intended to be in the direction of the PTO end - Tractor from the PTO pusher from the flywheel end.
What I found inside:
It has a cast crank with substantial counter weights. The rods are aluminum with canted big end parting plane. Either this particular engine just happened to be a good combination or the factory does not balance the crank. There is no drilling or machining of the crank that one would expect from the balancing operation.
The cam has a steel gear and is fitted with a compression relief mechanism.
The main bearings on both ends are plain bearing rather than ball bearings and the bearing surface is the aluminum casting. There are no bearing inserts. This isn't really a problem if the oil is kept clean, but will make overhaul more difficult. What was troubling was that the crank bearing surface was not as smooth as I would expect and should be polished better. It would likely fail "the penny test". The polish under the main seal is much better.
Conclusions:
It will make a good air-boat motor. Due to the small PTO diameter of the cast crank if the prop were to be attached at this end a third bearing would probably be a good idea. It may still be adequate for an inexpensive light plane but I'd consider the engine disposable at overhaul time. They must have passed the 1000 hr. test to be EPA certified, but this only means that they aren't burning oil or have leaking valves at the end of the test.
I will be buying a Honda GX690 to examine next. I still plan to test the HF engine on a test stand, but it's now not as high a priority as it was before this inspection.
The first problem is that the engine was back ordered and when I called I was told that they would not have another shipment for nearly 2 months. I canceled the order at that time, or so I thought. About a month later when I left the house I found a box setting in the driveway. It was a HF engine. The delivery driver did not ring the door bell and there was no signature required. The next day I received postcards from HF notifying me that the order had been canceled and a second saying that the order had been on back order for over 30 days and per UCC I could cancel the order. I called HF and was informed that my order had in fact been canceled. My bank account had not yet been drafted so I decided to wait and see what happened. Long story short my bank account did get drafted and I was stuck with the HF engine. I decided to evaluate it as planned rather than continue to try to get return the engine. They did honor discount coupon number. I don't know if they would if one were to buy from a store.
A few days ago I found time to unbox the engine and start examining it. Here is what I've found in no particular order:
First impression is that the fit and finish is actually quite good. If it had a Honda of a B+S sticker on it rather than Predator it would be believable.
Weight on my digital scale was 95 pounds with the air cleaner, muffler, and fan shroud removed. The removed parts weigh :
Air cleaner = 3 pounds
Shroud = 1.5 pounds
Muffler = 9 3/4 pounds
The engine can use 10% ethanol fuel but not E85. It comes with 2 sets of main jets for high altitude. They are different side to side due to the cheap intake/exhaust design, which is common to most of these V-twin industrial engines.
The oil cooler is plumbed with hose that uses spring type clamps. The oil filter base is integral with the case, unlike the Honda GX690 which is a separate part.
Carb mixture adjustments are sealed - as would be expected for an EPA certified engine. But at least they are there.
The stamped steel rockers look less than substantial. But then the valves are small and the single valve spring is also pretty small. The wear surface area on the shaft is probably a source of excessive wear, but a fix would be simple. The valve lash was adjusted properly.
The crankshaft PTO end appeared to be well machined with good finish and no tooling marks. A manual check of the end play seemed excessive and measured at .016" - a lot less than I had thought. It was still enough to prompt me to remove the case cover to look inside before running the engine. The gasket measured .020 thick so the end play could be adjusted by surfacing the thrust surface of the crankcase cover (both the cam and crank) as needed and assembling with no gasket and anaerobic sealant. I didn't pull the crank but it appears that the thrust is intended to be in the direction of the PTO end - Tractor from the PTO pusher from the flywheel end.
What I found inside:
It has a cast crank with substantial counter weights. The rods are aluminum with canted big end parting plane. Either this particular engine just happened to be a good combination or the factory does not balance the crank. There is no drilling or machining of the crank that one would expect from the balancing operation.
The cam has a steel gear and is fitted with a compression relief mechanism.
The main bearings on both ends are plain bearing rather than ball bearings and the bearing surface is the aluminum casting. There are no bearing inserts. This isn't really a problem if the oil is kept clean, but will make overhaul more difficult. What was troubling was that the crank bearing surface was not as smooth as I would expect and should be polished better. It would likely fail "the penny test". The polish under the main seal is much better.
Conclusions:
It will make a good air-boat motor. Due to the small PTO diameter of the cast crank if the prop were to be attached at this end a third bearing would probably be a good idea. It may still be adequate for an inexpensive light plane but I'd consider the engine disposable at overhaul time. They must have passed the 1000 hr. test to be EPA certified, but this only means that they aren't burning oil or have leaking valves at the end of the test.
I will be buying a Honda GX690 to examine next. I still plan to test the HF engine on a test stand, but it's now not as high a priority as it was before this inspection.
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