apwachholz

I've got a rather new OS 91 Surpass II and recently it has been giving me troubles. Idling seems to be inconsistent and just today when I tried to run the engine up it sounded like there was a metal "clang"-ing noise coming from it. When it throttled down, it was fine. Needless to say Ithink something is wrong (Duh!) and I'm not planning on running the engine any time soon. Here's my question:

When do you know ur bearings need to be replaced?

Iask this as Iwas told by someone that this might be the case. Any help would b greatly appreciated. Thanks All...

_me

w8ye

My Feedback: (16)

Sounds as though it is time for replacement

Edwin

My Feedback: (2)

When my OS91fs started not holding its idle and becoming finicky I tore it down and cleaned the carbon out of the cylinder and valves. Ran like new after that. I did the bearings about 2 years earlier because you could hear them as the crank free spun. Changing bearings isnt that hard. If I suspect, just do it and you'll know.
Edwin

apwachholz

Edwin -

How do you 'clean the carbon' out?I'm new to tearing apart engines (I've only been in the hobby for 2 years) but really want to learn how to be my own mechanic. And I t hink I'll go with your and w8ye's advice about replacing the bearings. The worst that can happen is the engine runs great after all is said and done - it's just the time it takes to do it. But I'm willing to learn....

w8ye

My Feedback: (16)

http://translate.googleusercontent.com/translate_c?hl=en&ie=UTF-8&oe=UTF-8&langpair=fr|en&u=http://epervier.sudluberon.free.fr/moteur4t/index.html&prev=/language_tools&usg=ALkJrhhLTUHci_UTpbuTsIw3JV4jplm azQ


This has been translated from French.

The direct link "Hot URL" part of RCU's editor will not pick up on the entire link.

You will have to manually copy and paste it to your address bar

w8ye

My Feedback: (16)

http://epervier.sudluberon.free.fr/moteur4t/index.html

Which is in French

You can run it through the Google translator?

Edwin

My Feedback: (2)

Some people dont like it, but I use the crock pot anti freeze method. Remove the carb, the glow plug, back plate, and head. Find a crock pot used or goodwill cause you'll never use it for anything else again. I use prestone non-enviromentally freindly antifreeze, but its mostly the glycol content that you want. Heat on low for at least 4 hours or up to over night depending on how bad it gunked up. (NOTE: if you heat it too long, like several days, it will turn the metal dark grey. Doesnt hurt anything, just looks.) Sometimes you have to use a wire brush and pick to clean off the really tough stuff, like the carbon. Right when you take the crank case out of the crock pot when its still pretty hot is the best time to remove the bearings. I use a battery cable puller to remove the prop hub, its a cheap tool. I also have an arbor press so its pretty easy for me but lots of guys prop up the crank case and use a board on top to tap out the crank shaft. The front bearing usually doesnt come with it. I make a little cross member that I can slide above the front bearing, hard to describe until you can see what you're dealing with. Others here will probably chime in with different ways to do it. There are lots of ways to do this depending on what you have for tools. Reheat the case to install new bearings.
For the carbon clean up, you need a dremel with a round wire brush and a crown wire brush. The crock pot loosens the carbon up pretty good. I use a pick set on any big chunks left. Then the dremel treatment. I also remove the valves. Be very careful, its easy to lose the valve stem keepers. They're just like on the big engines. I made a tool using 1/16" aluminum with a hole drilled to push down the valve spring with top piece. When you do this, I highly suggest you do it with everything inside a big clear plastic bag. If your hands slip, those keepers are easy to loose. At lest you have a chance of keeping them inside the bag. Learned that the hard way. Once all apart, I get after it with picks, dremel, and q-tips. This includes inside the intake and exhaust channels in the head.
Thats what I do in a nutshell. Others might have easier ways to do it too. Search around cause this topic has been talked about a lot. If you dont have the right tools, get them first and dont be afraid to ask questions. There is always a first time.
Edwin

apwachholz

W8ye / Edwin -

Muchas Gracias friends!

I appreciate your help on this, i really do. I'm not sure that there will be much carbon build up as the engine has only been run 12-17 times (first season was this summer) however, when I crack that bad boy open if it's needing the love, I know where to come back to for help.

Again, thanks everyone. And I'll be sure to post back with questions. Now, on to the disassembly......

w1nd6urfa

My Feedback: (4)

I recently disassembled mine after a crash [link=http://www.rcuniverse.com/forum/m_9133151/tm.htm]link[/link] so here's some tips:

- Bearings: the rear is large, so I heated up the crankcase using a hot air gun, just a couple of minutes then just knock the case on a piece of wood and voila! the bearing pops out. For the front I heated the crankcase again and used 3/8" wooden dowel pushing from the rear until it came out. You need a heat glove to hold the case.

- Valves: After removing the head you can see the state of the valves, usually the exhaust (smaller) valve will have carbon deposits and will not seat properly. The latter causes blow-by which ofcourse reduces performance, post some pics and we'll tell you if it needs cleaning or not. If yes you need some cleaning agent to dissolve the carbon, dremel with wire brush, q tips and lots of patience . WARNING: be very careful with the valve crown and valve seats, this part shouldn't be soiled anyway, so clean the valve face and stem only.

Seeing a 1000 RPM improvement after the above is a good feeling [8D]