engine question please?, 0s 91 4 stroke
 

hi here, i puechased a plane and it came with an OS 91 FS 4 stroke, the seller couldnt get the engine to start and the engine feels with no compression almost at all; any sugestions?recomendations? i have removed the liitle cap over the valves(lifters) and they dont move or react wen im turning around the propeler. its like they are frozen; do this mean anything? are they suppose to be movong wen ou rotate the propeler or not?
the seller told me that a year ago te engine runed very well and then he have strore the plane since then. regards.

RE: engine question please?, 0s 91 4 stroke
 

Sounds like the valve lifters are stuck from sitting. Yes, they are supposed to move when you rotate the propeller. Drip some WD-40 or other light oil down into the push rod tubes and anywhere else you squirt some oil and continue to rotate the propeller. Once the lifters/valves begin to operate the compression should return to normal. If its been sitting for a while it will probably need a good cleaning/oiling.

RE: engine question please?, 0s 91 4 stroke
 

Warming up the engine with a heat gun helps free them. And then some oil.

RE: engine question please?, 0s 91 4 stroke
 

I would suggest you remove the rear cover and look for rust first, if the inside is well rusted as many stored engines are, it will need to be cleaned before running. Rust is very abrasive and left in there it will act as a lapping compound and wear out the engine quickly. Alcohol is a good solvent for cleaning out the old oil and castor varnish, follow up with a light oilwhen you re-assemble the engine. WD-40 is not good for engines, it is mostly solvent and will not break down castor varnish.

RE: engine question please?, 0s 91 4 stroke
 

hi everybody,thanks for your reply.
i applied some heat, but nothing,anyway i didnt insisted too much, i went to look for " liquid wrench" oil,but havent found any around the area, so i have done some research on penetrating oil related sites, and some people for different purposes like to use PB BLASTER.
will PB BLASTER be harmless for rc engines? it will be safe to use it? any posibble harm to 4 stroke engines in the valve sistem if PB BLASTER is used? should i continue looking for LIQUID WRENCH? after the oils are aplied,and everything is working good, do i have to remove the oil from the engine? how would i clean it? if wen opeing the back plate is any rust, how i would clean or remove it? sorry i'm asking so many questions, but im the type of pilot that flyes but have no clue about anything technical. thanks and regards.

RE: engine question please?, 0s 91 4 stroke
 

The rocker arms and valves would have to be stuck in the open position. Not very likely, because when you turn the crankshaft and the lifters drop to the low side of the cam the valve springs would close the valves. Unless the valves, rockers and pushrod are so gummed up the springs are not strong enough to pull them back into the seats. If you can loosen them all well and good, but if that does not work, you need to check your cam gear. You may have lost a couple teeth. I had it happen to a 220 Saito. The prop will turn freely but nothing will move. You get no compression because the cam stopped with one of the valves still open.

RE: engine question please?, 0s 91 4 stroke
 

Use alcohol and a old toothbrush to clean the parts........


If the bearings are rusted, they will need to be replaced, can you remove the back cover and post a picture of the inside here?

RE: engine question please?, 0s 91 4 stroke
 

I have used PB Blaster on R/C engines many times...it will not harm your engine...it is good stuff.

RE: engine question please?, 0s 91 4 stroke
 

Turkey rcdude has it nailed:)

RE: engine question please?, 0s 91 4 stroke
 

thanks everybody. i were able to remove the back plate and here are some pictures:
how can i remove the rust with out taking apart the engine? is any liquid i can dip the engine in and will remove the rust? how i will clean the residual after? somebode has suggested alcohol, any type?rubbing 70%? please give me as many advises to do this the easy and safest way [lease. once again i'm not a tech person, and have never taken an engine apart. regards

RE: engine question please?, 0s 91 4 stroke
 

Hate to say this but you are going to need new bearings and the engine will need to be torn down to do it. There is no way to save the bearings, even if you could remove the rust from them, they will be badly pitted and fail soon anyway. With the parts removed from the engine it will be easier to clean

Are you a member of a flying club? If so, maybe someone there can help you clean up and repair the engine.

RE: engine question please?, 0s 91 4 stroke
 

That engine is not to purdy looking fer sure. I would have to agree that at least the bearings will need to be changed.
Turqui I use an old crock pot with Green Anitfreeze on low heat to remove stains and castor build up. This method has worked well for me, but needs to be used with some CAUTION the Vapors are Harmfull as well and the liquid itself is deadly to Animals & Humans. So don't drink it *L* Once the pot is contaminated it can never be used again for cooking.

An Engine that bad I would leave in the solution overnight,anything that is left a toothbrush will remove once its loosened. Like has already been said the bearings even if you did get them clean will be pitted. Paul @ RCbearings.com has them on the shelf at a good price.
Changing the engine bearings is not a hard thing to do, there are plenty of threads on here as to how it's done or if you feel your not up to the job either find someone or send it to someone that can change them for you.

RE: engine question please?, 0s 91 4 stroke
 

Hi there thanks everybody for your sugestions. I'm allready taking apart some used engines and shopping for bearings, and then I will start the research on how to take the engines apart and change the bearings and assemble the engines back together. I will be storing some used engines for long, and some new engines that have never seen fuel; what would be the best way to prepare and get this engines ready for some time stored. Any lubricants or additives to prevent rust? Also to prevent they getting stuck? thanks again, I promise I won't bother no more.regards.

RE: engine question please?, 0s 91 4 stroke
 

You aren't bothering anybody. Keep posting and keep asking if you need to.

RE: engine question please?, 0s 91 4 stroke
 

http://www.youtube.com/watch?v=S_HrTCCO-GY

Greg has three Youtube videos that will help you out. The engine that he's displays is an OS FS-52 but you'll get the point.

RE: engine question please?, 0s 91 4 stroke
 

what do you think about liquid wrench? safe ?good enough to u nfreeze the valves and disolve the rust inside the engine? any specific liquid wrench? because i know they make a couple types for different purposes. the alcohol to clean the oil and stains is regular rubbing compaund ?70%? it will be safe if i just fill a container with alcohol,rubbing alcohol 70% then remove the back plate of the engine ,also leave the carb open,and remove the glow plug, and then, submerge the engine inside the container with alcohol for a couploe days so alcohol goes inside as much it can?
i will continue storing some engines for some time, any special storing tips?
regards and thanks

RE: engine question please?, 0s 91 4 stroke
 

Stay away from long soaking in alcohol. It can have some nasty corrosive effects on the finish of the metals. Better to use oil based solvents especially if you're going to let your parts soak for a while. I my self like Marvel Mystery Oil, but there are plenty of others available from Wally World or the auto parts store. About your comment of bugging or disturbing anyoneAsk all the questions you want. Thats what we're here for. Your starting to become a REAL modeler when you start doing your own engine work. Not just another helpless instant gradification ,I'll just buy a new one and throw money at it type. Once you get the hang of engine building, you will find lots of smoking deals on motors that people give up for dead. With a little handy work and often a set of mail order bearings or a Frank Bowman ring, you can have a real nice motor for dirt cheap.

RE: engine question please?, 0s 91 4 stroke
 

Thanks again I really appreciatte your advises. Today I will continue taking a part few engines, and I will look at YouTube as recomended the disasemble and reasemble of the 91 4stroke. Today I will drive to the hardware store and will like please if you guys could tell me specific brand name of products, so I know exactly what to ask for, just the brands which you recomend or like to use because they do the best job and very safe.
1st:brand of product you like, have used, or would use, to disolve rust, clean engine, and unfreze lifters, valves, or anything stuck.
2nd:same thing as above, but now after disolvong the rust, what product can I use to clean or remove all that rust and dirt that have been disolved?
3rd:brand of product you use to put in the engine for protection for long time storage?
4th:brand of bearings aftermarket you guys recomend for quality and prices? I was doing a research and there are diferent type of bearings for every model and each made with diferent materials, wich is the most colon one to buy?
Once again; thanks and regards.

RE: engine question please?, 0s 91 4 stroke
 

Turqui clearly stated in [link=http://www.rcuniverse.com/forum/m_10338312/anchors_10342030/mpage_1/anchor/tm.htm#]post #1[/link], that the valve-train seems not to move, as the propeller is turned...

Although the prop could be loose on the crankshaft, I believe this means the camshaft is not turning...
...Or otherwise does not operate the push-rods.

It could be that a couple of teeth on either the the crankshaft, or the cam gears; have worn-off, or broken.
The cams could also be ground down to the base-circle.

If the above describes your situation, Turqui; the rusty bearings are the least of your troubles...
It will be much more expensive to repair too.

The bearings for the .91 Surpass are [link=http://www.rc-bearings.com/catalog/product_info.php?cPath=65_66_71&products_id=736]here[/link].

RE: engine question please?, 0s 91 4 stroke
 

If the push rods have fallen out of their sockets because the valves were stuck open, The pushrods will jam themselves beside the rocker arms and will not move with the engine turning over.

RE: engine question please?, 0s 91 4 stroke
 

Turqui...if you haven't gotten it yet, go ahead and get a can of PB Blaster, or Liquid Wrench, whichever you can get your hands on...either one will serve the purpose.

Completely dis-assemble the engine...
Use scraps of an old T shirt, a tooth brush and cotton swabs (Q tips ) to throughly clean all the parts. You're just gonna have to scrub the rust and crud off...because just soaking will not get all of it off.
You will probably need to scrape some rust off...use a small dull knife and some very fine sandpaper, like 600 or 1000 grit, available at Auto Body supply shops to carefully polish the Steel parts like the crankshaft.

When you put it back together, you can use "Air Tool" oil..it's made for pneumatic tools like they use at automotive garages / shops.

You can use Air Tool oil in all your engines, unless they are YS engines that have Silicone diaphrams.

If you feel you might need to, take pics and write notes as you dis-assemble the engines so you will have a better idea as to how they go back together.
Pay particular attention to which cam tappet came out of which hole, and which pushrod goes to which valve, because sometimes they wear at different rates. (the mating surfaces wear-into each other )

If you take your time and work methodically, you should be fine...we will help you if you have any problems.

RE: engine question please?, 0s 91 4 stroke
 

If you try the PB Blaster, do it outside at first. The smell stayed in my shop for days!

RE: engine question please?, 0s 91 4 stroke
 

I guess I don't really notice things like that anymore...
My shop smells like paint, lacquer thinner...all sorts of oils and cleaners...it's my "Man Cave"...don't have to worry about anyone else complaining ;)

RE: engine question please?, 0s 91 4 stroke
 

I just did an engine in the same kind of shape yours is, mine is a OS.48FS. Pretty much seized. I use the crockpot with antifreeze on low method for cleaning. Four hours to over night if you have to. It will look nearly new when done and even remove baked on oil from the muffler. A little tooth brush action on the tough stuff and your done. I rinse with water. Do this in a well ventalated area. Lots of info on this process here on RCU. I was hesitant to recommend this because you are learning to be a gear head. Make sure you have help to answer questions on what you find, how to fix it, and how to reassemble it. Its pretty satisfying to hear the engine run again good as new. NOTE: If you leave it in for too long, like days, it turns the aluminum dark grey. Not harmfull, just a color issue.
Edwin

RE: engine question please?, 0s 91 4 stroke
 

I almost never notice any smells, and I like most anyway. Paint, glue, gasoline, cleaners, and dirty engines. This is the only one I can remember that I didn't want inside the next time. My wife never comes down there either.