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Old Feb 19, 2013, 11:10 AM
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Originally Posted by Machzx View Post
This helps how?
My remarks addressed Earl's description of the engines, right above mine.

It was in regards to 'disposable' engines that need the prop-drive washer removed in a destructive manner, should you ever need to; G-d forbid; take it apart for maintenance...
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Old Feb 19, 2013, 06:15 PM
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Well I don't consider expensive 2.5cc competition engine asbeing disposable, but they definitely didn't make it easy to pop the prop-drive washer off.

Now then at least one major brand engine company does want people to buy new engines instead of fixing them though. They tend to go out of their way to "encourage" it too. I am surprised they didn't put on hard to remove prop-drive washers though.
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Old Feb 19, 2013, 06:53 PM
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Originally Posted by earlwb View Post
Well I don't consider expensive 2.5cc competition engine asbeing disposable, but they definitely didn't make it easy to pop the prop-drive washer off.

Now then at least one major brand engine company does want people to buy new engines instead of fixing them though. They tend to go out of their way to "encourage" it too. I am surprised they didn't put on hard to remove prop-drive washers though.
The only engine manufacturer I do know of to have included a puller in their package was the Saito G-60 WFV ignition engine. About 2000 were produced, in 1978 ! And for you gas-addicts, this one does run on gasoline. Mixture ratio with lead-free was 8il 1 for break in and 10il 1 for running, recommended oil was Yamaha special 2 stroke oil.
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Old Feb 19, 2013, 11:28 PM
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Originally Posted by DarZeelon View Post
It was in regards to 'disposable' engines that need the prop-drive washer removed in a destructive manner, should you ever need to; G-d forbid; take it apart for maintenance...
NO prop driver needs to be removed in a destructive manner if the correct method (heat, press, whatever) is used. The closest I know of to "destuctive" removal is with something like a Merco 35 where the prop driver is forced over splines on the crankshaft cutting corresponding splines in the driver. Of course, being plain bushed engines, there's never any real reason to remove the crankshaft unless you bend it.
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Old Feb 20, 2013, 01:50 AM
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Originally Posted by downunder View Post
NO prop driver needs to be removed in a destructive manner if the correct method (heat, press, whatever) is used. The closest I know of to "destuctive" removal is with something like a Merco 35 where the prop driver is forced over splines on the crankshaft cutting corresponding splines in the driver. Of course, being plain bushed engines, there's never any real reason to remove the crankshaft unless you bend it.
Brian,


Even if the manufacturer of an engine does offer a special, proprietary tool, to facilitate taking HIS engine apart, it will either be expensive and/or not usable for any other purpose.
Such a tool leaves the engine to bear the label "No user serviceable parts inside!"; the way I perceive it.

If an inexpensive, readily available battery terminal puller can be safely used; which will also be usable for other engines this person has; it is the limit of what I would consider a good investment.

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Old Feb 21, 2013, 10:21 AM
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Originally Posted by Reginald View Post
The only engine manufacturer I do know of to have included a puller in their package was the Saito G-60 WFV ignition engine. About 2000 were produced, in 1978 ! And for you gas-addicts, this one does run on gasoline. Mixture ratio with lead-free was 8il 1 for break in and 10il 1 for running, recommended oil was Yamaha special 2 stroke oil.
wow, neat mix of new and old going on there along with a "proper" CM-6 plug. always thought saito was exclusively 4-stroke, guess i learned something new today....thanks!
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Old Feb 21, 2013, 11:51 AM
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Saito first made model steam engines and accessories. They still hake some spectacular multi-cylinder steam engines too. I beleive that the Saito two cycle .60 engine was probably intended for pattern flying at the time. But with gasoline instead of glow fuel. There are countries or locales where a gasoline fueled engine would work well as glow fuel would be very difficult to impossible to obtain. It is a modern Schnuerle ported engine and is very powerful. It isn't SAM legal as it is so powerful in comparison to the old vintage spark ignition engines. They made the engines in a front intake and rear intake version as well as air and marine versions. Saito sort of likes to do things different and not follow the crowd. After that .60 engine Saito went with four cycle engines only.
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Old Feb 21, 2013, 12:50 PM
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Originally Posted by earlwb View Post
Saito first made model steam engines and accessories. They still hake some spectacular multi-cylinder steam engines too. I beleive that the Saito two cycle .60 engine was probably intended for pattern flying at the time. But with gasoline instead of glow fuel. There are countries or locales where a gasoline fueled engine would work well as glow fuel would be very difficult to impossible to obtain. It is a modern Schnuerle ported engine and is very powerful. It isn't SAM legal as it is so powerful in comparison to the old vintage spark ignition engines. They made the engines in a front intake and rear intake version as well as air and marine versions. Saito sort of likes to do things different and not follow the crowd. After that .60 engine Saito went with four cycle engines only.
odd that they hobbled it with points though. transistorized ignition or even CDI was just as easy to do in the '70 as it is today.
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Old Feb 21, 2013, 03:26 PM
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Back to the OS 55AX, I would expect that it is almost easy to pull the crank and replace the bearings. OS usually does really good machining on their stuff, so one probably doesn't have to over do it to pull the crank out. The drive washer uses a D shape so it isn't using a collet. I think the bearings would likely almost fall right out when you heat up the crankcase and wack it on a board carefully so that inertia does the work. Just like in the video I mentioned earlier. Some of the other engines I have used are like that. You just heat up the crankcase good and press the crankshaft out. If the rear bearing doesn't come out you can reheat the crankcase and give the crankcase a swift wack on the table or board and inertia pulls it right on out. The front bearing usually comes out easily enough, but sometimes a rod inserted through the back to catch the inside race edge and a few taps with a block of wood works it out. One can use a bearing puller tool too. I would suggest watching the part 1 and part 2 video clips to get an idea of what is entailed. Using tools and or a press to do the process is best, but you don't really have to.

I don't have any newer more modern OS engines that I have replaced bearings in yet, but I have done bearing replacement with numerous other engines over the years. I think the bearings in the Saito engines were the hardest to get out and replace. But those pesky cam bearings in older OS and Enya four stroke engines can be tricky.
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Last edited by earlwb; Feb 21, 2013 at 03:28 PM. Reason: typo correction
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Old Feb 21, 2013, 04:53 PM
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Originally Posted by earlwb View Post
...You just heat up the crankcase good and press the crankshaft out. ...
Earl,


Heat will not help you remove the crankshaft. The bearings expand as much as the crankshaft, so the crankshaft remains as tight in them, as it was when cold.
So, it must be pressed out of the bearings with the crankcase still cold.

Only after it is out, the crankcase should be heated to remove the Bearings.

Please watch those video clips again to be sure.
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Old Feb 21, 2013, 05:06 PM
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Originally Posted by DarZeelon View Post
Earl,


Heat will not help you remove the crankshaft. The bearings expand as much as the crankshaft, so the crankshaft remains as tight in them, as it was when cold.

smaller mass of the bearing will heat up and expand much quicker than the larger mass of the shaft....heat also has a hard time passing from one part to another, even with a press fit, so it also helps if the heat is concentrated on the bearing. just recently had to do this to remove the spindle of my lathe without damaging the bearings as they run around $500 for the pair.
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Old Feb 21, 2013, 05:27 PM
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Well I use a Heat Shrink tubing gun to heat up the crankcase. The fellow in the videos used a propane torch to do it. The torch heats up the crankcase faster than the heat can get down to the crankshaft. The aluminum expands at a different rate than the steel bearings or steel crankshaft too. Now then quite a few people place the engine into their ovens at home and heat the engine up in it for a while and it works well too. But I prefer not heating up the engine's crankcase and crankshaft in a oven as it is more slow ahdn heats up the crank more..
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Last edited by earlwb; Feb 21, 2013 at 05:28 PM. Reason: type correction
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Old Feb 21, 2013, 07:46 PM
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Originally Posted by ZAGNUT View Post
smaller mass of the bearing will heat up and expand much quicker than the larger mass of the shaft....heat also has a hard time passing from one part to another, even with a press fit, so it also helps if the heat is concentrated on the bearing. just recently had to do this to remove the spindle of my lathe without damaging the bearings as they run around $500 for the pair.
As millwright we use heat quite often to remove and install bearings
It is standard practice and most time the only way to do the job quickly and without damage
We are talking bearing that cost thousands
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Old Feb 21, 2013, 07:49 PM
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On ya we cut them off with a torch too
Also a standard practice in the field
Of course this is on large applications
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Old Feb 21, 2013, 08:25 PM
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I have had to use a metal cutting tool a couple of times to get the bearing off of something before. That happened when the inner race comes out and the bearing comes apart, leaving the outer race in place. Of course with a Dremel tool it can take a while and use up a number of the cutoff discs. When the bearing itself is pretty small I had to fabricate a puller tool to get it out.

I think the most interesting way to remove a ball bearing race that was stuck inside a really expensive aluminum part one time, was when the machine shop used nitric Acid to dissolve it. Before then I would not have thought that nitric acid wouldn't dissolve aluminum. But since seeing that I have used it a few times to remove broken off taps, bolts or screws too.
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