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Old May 11, 2016, 12:28 PM
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Pedro Salomón
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Maintainance for a 4 stroke OS 70 Surpass I

Hi Guys:

I have this engine wich is disasembled for cleaning pourpouses as i got it from ebay but dirty and sticky, i managed to move propeller fut feels with no compression so i decided to open it.

I can´t take the piston pin out of the piston, so i can´t continue with disasembling it. i just took out the plastic cap in piston pin wich is pretty stuck to the piston.

What do you recommend to take the pin out? can I heat the engine?, any liquid WD-40?, glow fuel?, paint thinner?.

I am driving crazy with this
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Old May 11, 2016, 03:57 PM
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I recently overhauled a couple of gummed up OS engines. Heat will help loosen the stuck wrist pin. If you removed the plastic end pad, you can try inserting a tapered nail set into the center hole in the pin. That eventually worked for me.
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Old May 11, 2016, 07:42 PM
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Heat is good, but you should also introduce a cleaning agent, as well.

Methanol is the basis of the original fuel and works well, even if left to soak at room temp. Depending on choosing to warm it up, flammability can present problems so there is another method we have used for decades.

If you have a crock pot dunk the bits in glycol and heat it for a while. This is toxic so two rules: Do it outside or in a well ventilated area and never use that pot for food prep ever again.

You would be surprised at how well this works. As little as 30 minutes can take a clogged, congealed or one with burnt oil and make it look new.

I found a pot at a resale shop for $8. The glycol can be filtered and reused so the price should be manageable, especially if used often. I rebuild numerous engines for myself and friends so it works out.

Along with some recommendations one warning

A) Glycol is not harmful to any gaskets or rubber O-rings or seals, so should be O/K if engine mostly left intact.

B) You will want to open the case, easiest by removing the rear cover.

C) DO NOT rotate the crank until this has been soaked. Even hardened lube can damage the bearings if left in the races. Wait till it has been soaked first. It will likely free up the ring, as well, so you can remove it to clean inside the groove.

D) If the bearings are good you need to rinse the engine of remaining glycol and try and get any contamination out. You will need to treat the bearings and any other ferrous bits with oil immediately after drying as corrosion can begin rather soon. It also helps lube any moving bits.

Now the warning: When the parts are removed from the pot they can be extremely hot, so try to avoid direct contact. I made a screened cage with a handle to place all the pieces in and can pull them out and rinse without risk of burns.


Now to servicing the engine. OS have removable heads so you can take a closer look at the valves and seats. Most often the exhaust will be the one with the most carbon or burn lube so that is the most likely to have some caught between the valve and seat. Ensure everything is clean and free.

I find bearings are one of the most vulnerable so most often replaced. If the engine has not been taken care of or stored properly they can be damaged in ways that may not show up till later. A good check can make life a lot easier.

These engines have a higher parts count, but if properly serviced can be completely torn down and reassembled relatively easily. Proper cam timing is the most critical. There are some good resources with pics and instructions if you require.

Where are you located?
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Old May 11, 2016, 10:50 PM
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It is good to see a good and straight forward reply with the pertanent info he op asked for
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Old May 12, 2016, 11:22 AM
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Hello Cougar429 thanks for your detailed explanation, will try this with the engine and then see if the piston pin comes out. I am located in Puebla, Mexico.

Please, send me those resources as one pic is worth thousand words...jeje.

Cheers.
Pedro
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Old May 12, 2016, 07:26 PM
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No problem. Even if the previous poster was being sarcastic, figured if the info was no help to you, may have been useful to anyone else finding this thread.


Here are a couple of good threads:

http://www.rcgroups.com/forums/showthread.php?t=863308

http://www.rcgroups.com/forums/showthread.php?t=1865757
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Old May 12, 2016, 07:31 PM
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No sarcasm was intended , I was glad to see an honest post , used to that datsunguy and his buddies trashing such threads
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Old May 12, 2016, 07:40 PM
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No problem and all too true. See too much of that.
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Old May 13, 2016, 07:02 AM
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http://www.osengines.com/parts/xr34700.html

Here is a parts list for the Surpass II, I don't know how closely they are related if at all. Manual too.

http://manuals.hobbico.com/osm/34000-manual.pdf

Cougar, the big brown truck is dropping an OS .95v here today. I'll report, it'll be a few days, I am re-charging the AC system on my truck today and leaving for Missouri to fish for a week tomorrow. Sometimes fun gets in the way fun.
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Old May 13, 2016, 07:12 AM
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See, that's why you want an amphib or two. Fill in the time between filleting.
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Old May 13, 2016, 07:16 AM
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Walleye's are good, we're going to Stockton Lake we usually stop at the Bass Pro shop in Springfield on the way.

The .95v should fly a pretty good floater.
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Old May 13, 2016, 12:36 PM
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cougar thanks for the links, fist one is great ! made me wish to have a blasting machine, great restoration results. Second one, a lot of useful info but no pics.

Cheers.
Pedro
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Old May 14, 2016, 08:16 PM
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Hi Guys, well after hours of trying to get piston pin out, I decided to sacrifice conecting rod as i have a spare one. So, i dremel conectin rod and broke it in the middle very carefull way with out touching other parts.

Once piston was out i needed to use the hammer like 5 times to take the pin out, it was really stuck and gummed up.

Well, i reassambled the engine today and had a run, it is performing well in high speed but need to work on air-fuel mixure so it stays runing on low speed.

Will se if i can up load a video of first re-run today.

Cheers,
Pedro.
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Old May 15, 2016, 05:13 AM
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Quote:
Originally Posted by harrier81 View Post
Hi Guys, well after hours of trying to get piston pin out, I decided to sacrifice conecting rod as i have a spare one. So, i dremel conectin rod and broke it in the middle very carefull way with out touching other parts.

Once piston was out i needed to use the hammer like 5 times to take the pin out, it was really stuck and gummed up.

Well, i reassambled the engine today and had a run, it is performing well in high speed but need to work on air-fuel mixure so it stays runing on low speed.

Will se if i can up load a video of first re-run today.

Cheers,
Pedro.
That is truly unfortunate. With the proper application of heat , oil, solvents, and patience that pin would have come out. I have yet to ever have to resort to destructive means to get a wrist pin out.
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Old May 17, 2016, 03:02 PM
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Video of engine running after major surgery.

https://www.facebook.com/psalomonmx/...type=2&theater
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