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Thread: The Rope Trick - Field Repairs 101

  1. #1
    soyAnarchisto's Avatar
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    The Rope Trick - Field Repairs 101

    This years trip to Oshkosh was a HUGE learning experience for me. Wait, i need to underline that word: HUGE! I had a fantastic time at Hew Holstein and Oshkosh - and the Crazy Daisy didn't come in DFL in the STOL comp in spite of my first attempt in the comp was only my 3rd landing below 5000ft MSL. I met some fantastic people - as usual - and barely made it out of the North Fond Du Lac camping spot for vintage aircraft at OSH. Had a great flight up to Washington Island.


    The trouble started on the way home. We departed New Holstein at 7AM for an uneventful arrival in OSH and parked in post-war boom planes and made it over to hear Bill Rusk talk about the ins and outs of building an experimental supercub in the Homebuilder Hangar. Departed by 11AM west bound and made it 3 hours west to this awesome little spot in Minnesota - Rushford, MN - great airport by the way - nice grass apron to land on, showers, free burgers and a a very pretty spot on a ridge in the hills. Shot the shite with a couple of the hangar rats, and after an hour went to move on.


    Since the J3 was still warm, I switched on the mags and hand propped her normally and she fired on the first go - like she most always does. This time around, somethin ain't right. Vibrations, weird loping, ran really rough. Oh no. I run her up and do a mag check - which had higher than normal rpm drop - but still only about 75 rpm - so that wasn't too bad. Taxied out to the runway to give her a go. Throttle up - something had shite the bed - won't make full power and max rpm is only about 1700 (normally about 2350 is takeoff rpm). I aborted the takeoff and taxied back to the ramp.


    Once shut down - I get out and pull the prop through. Once - okay. Second time - okay. Third time - hey that ain't right and the prop swings through a full rotation. Hmm. 1 jug isn't making compression. But which one? I start pulling spark plugs. Put a thumb over the hole as you pull through - you should get 3 that suck in - and 1 that pushes out. If you don't get a good push - that's the jug that isn't making compression. Mine was #2.


    I pull the rocker cover, and sure enough. #2 cylinder exhaust valve is stuck open (compressed). This is not what you want to see:





    Great, now what? We're in a little airport in the middle of nowhere - and everybody who is anybody is 200 miles away at Oshkosh. Fortunately we'd just been pounding beers around a camp fire with a salty lot of cub pilots. I was in the back listening and taking it in - but obviously not enough - talk of the rope trick. I remember hearing about it - but didn't fully understand what it would (could) be used for. But hell, I can't walk back to Colorado - so between myself, a fellow PA-12 driver who was travelling along the same route and a couple of the hangar rats - with some phone in instructions from more senior and well traveled aviators pieced together the procedure. It goes something like this:


    #1 - get a beer - you're going to be here more than 8 hours and you will need something to cry in if this shite don't work
    #2 - get your tie downs - you do have tie downs don't you dipshit?
    #3 - shine a light in the spark plug hole and pull the prop through till the cylinder is bottom dead center - farthest away from the valve - maximum volume in the cylinder.
    #4 - push in about 10 times more rope than you think is necessary into the spark plug hole. Hope your rope is fairly clean and reasonably soft and try to keep it from getting under the valve
    #5 - turn the prop - pushing the rope and compressing it on the top of the valve - and hopefully push it back into the valve guide.
    #6 - If nothing happens - or the valve only partially comes out - pull the rope out and try again. you may need to pull the other spark plug and use safety wire or something to keep the rope from getting under the valve and preventing it from pushing in. Pull the rope and go back to #4. Mine took almost 15ft of rope in the cylinder - more than you think it will take.


    Voila! Wait - i just started drinking beer? Can't I go fly it now? No bueno compadre - that puppy is VERY likely going to stick again as soon as you pull through. Don't believe me? Wait don't try it yet - you'll get your chance soon enough. This is time for another trick:


    "Staking" the valve: You need a hammer and a block of wood. And some Marvel Mystery Oil or some kind of oil and something to squirt it as far into the valve guide as you can - which won't be very far. Put the block of wood on the rocker arm, and give the valve some whacks - if it sticks - use the rope trick to push it in and out. You're going to be doing this a bunch of times - trying to clean off whatever gunk is built up on the valve stem or in the guide. Maybe, just maybe if you hold your tongue right and the stars and moon are aligned - this will get it freed up enough. It's doubtful - but you might get lucky. Spray Marvel Mystery oil in the valve guide, in the air box, put some in the fuel - and more in the oil - anything you can think of to get more lube in the induction system. Do a stuck valve dance - it's pretty similar to a rain dance. Pray to your maker.


    Now if you can get it to stay unstuck while you pull her through on the prop - you might be lucky enough to get it started. Me? No joy. That shite is stuck like the grizzly's winter butt plug. She ain't movin!


    Now it's time to get serious. Survey your inventory of available tools and expletives - cause you are very likely going to need some you ain't got. Well, I had plenty of expletives - but the only tools I had were a hatchet and a block of wood. After raiding hangars and getting help from more salty dogs I wrangled up some more required tools:


    1) dental floss - hygiene is important - but not as important as this stuff - and no a toothpick ain't gonna cut it
    2) valve spring compressor - what you say? a J3- driver doesn't travel with a valve spring compressor tool in your emergency tool kit - SOL
    3) 1/4 coarse thread eye bolts or
    4) a piece of bar stock and a drill
    5) 2 large screwdrivers
    6) Safety wire, coat hanger, grabber tools, magnets anything you can find that is useful for fishing
    7) Scotch brite pads
    Marvel Mystery Oil - I put that shite on everything


    What the hell is this shite you say? Dental floss? You must be out of your mind! What the hell are you going to unstick an exhaust valve with dental floss? Pay attention grasshopper - skool is about to be in session.


    Now shite's about to get real. You gotta remove the springs and the rocker arms. So if you have no valve spring compression tool - you gotta MacGyver something up. Hopefully you are smarter than I and travel with 2 eye bolts that you can screw into the rocker cover bolt holes and fashion 2 screwdrivers through to get leverage to press down the springs and remove the keepers. Careful of your fingers. No eye bolts? Take bar stock and use the valve cover as a template - and make a bar that will go across the bolts that you can use to get the screwdrivers under to press down the springs. Take the exhaust springs out - and don't drop and lose the keepers. Usually it's the exhaust valve that sticks because the intake is closed during combustion. Tap out the bar that holds the rockers on. Don't mix them up - you'll need to reassemble this thing sometime if you want to fly it out of the hole you are in.


    Now you should be staring at a stuck valve. Get your dental floss. Tie a beautiful fly fishing knot around the end of the valve stem. Or just tie a lot of knots. But not too many. It can't be bulky. Now with a tap or screwdriver, or something - gently start tapping the valve into the cylinder. Yes - ALL the way into the cylinder! But, but, but... How will the engine run? Patience grasshopper.


    Use safety wire or whatever to fish the dental floss out of the top spark plug hole. Now pull the valve stem out. The valve can't come all the way out cause it's too big for the spark plug hole - but you should be able to access a LOT more of the valve than you can through it's valve guide. Get your mystery oil and scotchbrite pad - and clean the gunk off the valve stem until it's shiny as a whistle. Use what you got. Careful not to score or damage the valve - but if all you have is a knife and no scotchbrite - it's better than rotting on the side of the AlCan waiting for winter or the Alaskan state bird to suck you dry from the inside out. Also you're going to need to clean out the inside of the valve guide. What's that - you did remember to put the right size reamer in your emergency tool kit right? Of course you didn't. Use soctchbrite twisted up on the inside. Usually the most gunk is closest to the cylinder which will be very hard to reach. If you can get a wood dowel, or fiberglass tent pole, or whittle a stick - cut a notch to hold your scotch brite and twist it in the hole. If you can get access to a cordless drill - even better to spin it around and clean the walls of the valve guide. Whew. That took a while didn't it! Feels good right?





    Yeah, but don't don't start feeling too good about your jury rigging skills - you still need to get this thing back together. Now you have a valve rattling around in your cylinder. Make sure you lube that sucker up with Marvel, or KY or whatever you have laying around. Time to go fishing. Prepare yourself for that long list of mother-sucking, blankety-blank, piece of doody cuss words - you're gonna need them. Make a little hook out of the end of your safety wire and run it down the valve guide. Use another one to push the floss over and fish it back out through the hole God intended it to go through. Just pull right? It's go easy, right? Fat chance sucker. Prepare yourself for reality. A lot of fiddling will get her started - and you're going to break 3 pieces of dental floss before you realize that thing is tighter'n a frogs butt. Hmm... Get her lined up as best you can - and use your rope trick again. Go easy. Feed in as much rope as you can in there and try to keep it behind the valve. Press against the back side of the valve with the cylinder by pulling on the prop. Remove the rope and reposition it if you need to as it goes in part way. Get it all the way back out. All the way.





    Now time to re-assemble the rocker and springs. Use your handy dandy valve spring-a-ma-jigger to get the springs on and compressed while you try not to sever a digit trying to get the springs in. You need at least 1 other set of hands - hopefully you're not alone. Lube up the rocker arms and reassmble both the intake and the exhaust. Clean all your spark plugs - especially the bottom ones - cause they're probably fouled up with a lot of lead deposits. Put the right anti-sieze on it - if you have it and torque - if you have a torque wrench the spark plugs. Finish your beer. Have another if you need to.


    Pull the prop through and make sure she's freed up and the valves are operating. All good? Fire her up. Do a run-up. Have the sober pilot take her for a few laps around the pattern in case she wants to go tits up on you in air. Now toss all your camping gear and moose antlers back in the plane and fly her the 12 hours home - including 45 solid minutes of VFR on top of 200ft overcast - in a 1946 J3C that had a stuck valve only an hour ago.


    Then clean your undies....


    Thank you SO much to Mr. Mike Therm, of Rushford, MN - owner of a beautiful Fairchild for passing along tribal knowledge of the Rope Trick. This fine gentleman saved my hide, and if you are ever in the area - please, please, please stop into this GREAT little airport and spend some money on their cheap avgas and say hi.


    Last edited by soyAnarchisto; 08-04-2014 at 06:00 PM. Reason: corrected spelling
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  2. #2
    soyAnarchisto's Avatar
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    Also a huge thank you to Ms. Windy for sticking around in time of need in case I needed a ride and helping to figure out all this stuff. Also all the folks who helped via text, phone, facebook, and sc.org with helpful suggestions. We got'r'dun and home safely and I really appreciate all the help I received.

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    RaisedByWolves's Avatar
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    you can also put a small telescoping magnet in your tool kit, to remove the keepers and to fish the valve back out. and I've had to use the cyl, coming up to help push the valve(gently) back in. Fun isn't it?

  4. #4
    SJ's Avatar
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    Used it many times on my old Cessna 170 before I discovered Marvel...

    sj
    "Often Mistaken, but Never in Doubt"
    ------------------------------------------
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    Is the intake valve rotating properly? In the picture it appears to be stuck in one position? Maybe it's the picture and it's just oil on the stem. Or maybe it has caps?

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    Cub junkie's Avatar
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    Never done it on a cub but have on a C-150. Much easier working height. In the mid '60's my dad had six continental powered patrol airplanes. We got real familiar with this technique.

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    mvivion's Avatar
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    Great write-up and documentation. Congrats in getting it done!

    Thanks for sharing.

    MTV

  8. #8
    cubdriver2's Avatar
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    Soy if your going to fly open cylinder small Continentals and burn mostly 100LL get your tools in the baggage for the next time.

    Glenn

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    soyAnarchisto's Avatar
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    intake valve was working properly - the exhaust valve is the most common culprit - apparently due to excessive amounts of lead in todays low lead - trick is to mix it down with mogas if you can get it - or use TCP as an additive to yer fuel

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    Great write up about your adventure! Now come up to LMO and I'll fill ya up with some mogas. It's all my Pacer gets when at home, 91 octane ethanol free, cheaper than LL, and no more fouled plugs.

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    supercub's Avatar
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    Take both plugs out. take the rocker off etc. once you get ready to feed the valve back into the cylinder, use some mechanical fingers up thru the bottom plug hole while looking with a flashlight thru the top. Mechanical fingers can be bought at any auto store, Home depot etc. Don't forget to clean the guide too...........a very precise size reamer will do the job.....just don't go to big. Use the mechanical fingers to reinsert the valve in the reverse of removing it. Once started in the guide........use a magnet in the guide to pull the valve thru the rest of the way. Don't forget to lube everything as mentioned above. I've done lots of these using mechanical fingers..............works great. One other thing...........believe it or not..........sometimes valve sticking (coating) is an indication of a cracked cylinder.........so you might want to boroscope the cylinder when you can. Oh ya, instead of all that rope, just use a couple of large screw drivers and gently pry out against the spring cap to get the valve stem extended for removal of the keeper a rocker pin. The whole thing should take less then an hour............obviously if tools are handy.
    Last edited by supercub; 08-05-2014 at 12:25 AM.

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    jrussl's Avatar
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    Very entertaining write-up Greg! I am glad everything worked out well.

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    soyAnarchisto's Avatar
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    Thanks for pointing that out. I'll have a look at the intake valve again, too.

    Quote Originally Posted by qsmx440 View Post
    Is the intake valve rotating properly? In the picture it appears to be stuck in one position? Maybe it's the picture and it's just oil on the stem. Or maybe it has caps?

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    Quote Originally Posted by soyAnarchisto View Post
    Thanks for pointing that out. I'll have a look at the intake valve again, too.
    Yes I wasn't saying it wasn't working properly and I don't know the parameters of your engine but normally valves need to rotate some to keep the seat clean and have even wear. On most (motorcycle) (hundreds) heads I have redone if they had a valve that had not been rotating they would wear oblong as the valve always returned to the same relative position. You could see it when you cut a new seat and the cutter would cut on two opposite sides first before leveling out the seat. Again I don't know your engine but I noticed what appeared to be a wear pattern indicating a "stopped" valve. Maybe some of the aircraft mechanics on here could comment with some real advice. Perhaps it's normal for an aircraft engine??

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    Always happens at the least opportune time. Happy endings are always good. I use Decalin from Aircraft Spruce when I put 100LL in my Rans, it's a lead neutralizer. LeAnne and I left Osh Saturday morning and arrived home in Alb only this morning. Beautiful trip home with some incredible grass strips but weather galore. Must have flown through at least 6 Sigmets. Next time I may stick with the southern route but great experience and adventure. It's nice to have a great 2nd stick who loves thermals (glider pilot)

    Arnold
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    mike mcs repair's Avatar
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    good post...
    I have heard of it but never needed to do it.. I got the local engine shop guys # to call if it needs done

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    Speedo's Avatar
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    Quote Originally Posted by soyAnarchisto View Post

    Thank you SO much to Mr. Mike Therm, of Rushford, MN - owner of a beautiful Fairchild for passing along tribal knowledge of the Rope Trick. This fine gentleman saved my hide, and if you are ever in the area - please, please, please stop into this GREAT little airport and spend some money on their cheap avgas and say hi.



    In the "It's a small world category," I met Mike Therm this year at Oshkosh and he spent a good deal of time telling me about his Fairchild. I agree with your assessment: he's a great guy.
    Speedo

  18. #18
    hotrod180's Avatar
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    I did the "rope trick" a couple times on my old 170 to fix a stuck valve. The correct reamer to clean up/resize the exhaust valve guide was a .437". The toughest part of the job was compressing the valve springs to remove/reinstall the springs & keepers. I used a homemade tool someone had cobbled up, it worked but not too well.

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    jjack's Avatar
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    Hey Soy, shove that 3 in the back and get an 18! Then you can have double the trouble!
    hope your well!
    that Windy is something too, a true contribution to aviation !
    JohnnyJackson

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    I thought someone was posting my story. Georgia Bill and I had this exact same problem on our J3 on the way to New Holstein. After camping in Washington IA we discovered one cylinder with ZERO compression the next morning. An experienced A&P was not 50 feet away and unstuck our exhaust valve and cleaned out the sticky valve guide. We were on our way in no time. MMO now goes in each tank.

  21. #21
    nesincg's Avatar
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    Quote Originally Posted by TulsaDave View Post
    I thought someone was posting my story. Georgia Bill and I had this exact same problem on our J3 on the way to New Holstein. After camping in Washington IA we discovered one cylinder with ZERO compression the next morning. An experienced A&P was not 50 feet away and unstuck our exhaust valve and cleaned out the sticky valve guide. We were on our way in no time. MMO now goes in each tank.
    I'm guessing Greg was sitting behind us in a state of calmness when you were tell me about your stop in Iowa. I don't think either Greg or I were in a condition to pay much attention. I'm glad he wrote this up because that is some funny stuff.
    The aviator formally known as 89.

  22. #22
    WindOnHisNose's Avatar
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    How often do you suggest MMO be added???

  23. #23
    cubdriver2's Avatar
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    [QUOTE=WindOnHisNose;606how often do you suggest MMO be added???[/QUOTE]


    First you need to get a prescription then on your pancakes every morning.

    Glenn

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    soyAnarchisto's Avatar
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    According to the thrush driver who gave me a quart - or it could've been Deano - I don't recall... the precise amount of MMO to add to every tank is 1 "glug-glug" - in every tank - I don't think the size of the tank matters - though there are something that resembles instruction on the side of the bottle - maybe I'll get around to reading them some day and see what it says

    the real trick is to cut down your 100LL with mogas if you can get it. Decalin or Alcor TCP (tri cresyl phosphate) is the "lead scavanging" additive that folks use.

    JJACK, that Rusk feller almost has me convinced I can build an 18 - we'll see - for now I gotta run what I brung. Hope to see you end of September - gonna be in Nags Head for a week and will be at the Manteo Island bluegrass festival - with the 3

    TulsaDave - it was your story around the camp fire where I first heard about this - if I'd have been drinking less I might have been able to put 2 and 2 together and figure out I shouldn't be running straight 100LL for a couple hundred hours all phat, dumb, and happy-like

    Quote Originally Posted by WindOnHisNose View Post
    How often do you suggest MMO be added???

  25. #25
    soyAnarchisto's Avatar
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    Marvel Mystery Oil! I put that $_hit on everything!


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    Neat. On a J-3 it only takes about 45 minutes to remove the cylinder if you do not have the right kind of rope. I have had a couple of these, although the valve was not bad enough to stick when actually operating - just bad enough to feel it when pulling through. In about two hours we pulled two cylinders, got the baked- on crap off the valve stems, and were flying again.

    I agree - a steady diet of 3/4 auto, 1/4 LL, plus some MMO just to make sure, and I go years without problems, flying every day.

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    I have not seen anyone mention it but there is another way to take valves apart with the head on the engine. If you pump the cylinder up with air as in a differential compression test, you can compress the valve springs and remove the keepers and then the springs. Let the air out and the valve can be lowered into the cylinder. I have used this trick in the past to change valve seals on engines and it works real good. The valve is really stuck in the head with the air pressure. This wont work of course if the valve is still stuck open when you go to work on it.

    Also the auto parts stores sell a handy valve spring compressor which again is meant to be used when the head is still on the engine.

  28. #28
    soyAnarchisto's Avatar
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    I also just learned that the cylinder in the picture is not #2 - it's #4 actually.

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    soy, I always figured that J-3 pilots couldn't count past three... At least I can count to eighteen, just not with my shoes on.

    A really helpful string that you started though.

    Thanks. cubscout

  30. #30
    soyAnarchisto's Avatar
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    How to count to 18 with only 1 hand:

    3, 5, 11, 12, 18

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    Quote Originally Posted by qsmx440 View Post
    Is the intake valve rotating properly? In the picture it appears to be stuck in one position? Maybe it's the picture and it's just oil on the stem. Or maybe it has caps?
    Those engines don't have roto coils. I do know the IO470's and IO520's only have them on the exhaust valve.

  32. #32
    Steve Pierce's Avatar
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    Great write up. Got to do this recently on my brothers J3 about 60 miles from home in a 20 kt. wind. Those Airstreak tires make the engine go up and down a lot, like working on a sea plane in the surf. I have used a coat hanger and some sandpaper before when no other tools were available.
    Steve Pierce

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  33. #33
    RaisedByWolves's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Great write up. Got to do this recently on my brothers J3 about 60 miles from home in a 20 kt. wind. Those Airstreak tires make the engine go up and down a lot, like working on a sea plane in the surf. I have used a coat hanger and some sandpaper before when no other tools were available.
    Isn't is fun to do when the plane is trying to fly and you have a fuel strainer for a screw driver and no other tools? Ha ha.

  34. #34
    soyAnarchisto's Avatar
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    Now that the engine is back home, I have it in my IA's shop along with the obligatory blank check and an intravenous tap to my bank account. Although I've not seen inside the rocker covers since I buttoned her up in MN, but I'm pretty sure what you see in the picture is a drop of oil hanging on the lower part of the valve. An optical illusion making it look like all the wear is on the top edge. I will double check still though.

    Quote Originally Posted by TrentF View Post
    Those engines don't have roto coils. I do know the IO470's and IO520's only have them on the exhaust valve.

  35. #35
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    I'm going to get a chance to use the rope trick on Friday. Found 64, 78, 78, 78 during the conditional on the SQ-2, and could hear air in the exhaust. CHT's are even so I was hoping this was just some carbon or lead build up. I use Marvel Mystery Oil about every other fill up to combat lead build up but decided to run a few tanks of fuel with TCP added to it. Just finished that and instead of doing another compression test I decided to buy a borescope (ouch!) so I could actually see what is going on. Am pleased that the exhaust valve has a standard burn pattern, so nothing detrimental has happened yet. I could also see a little black carbon build up in one spot between the valve and its seat. So Friday I'm going to fill the cylinder with rope, pull the valve spring, and lap the valve to the seat. Hopefully that fixes the problem. Crossed fingers & toes.
    Thanks McAlpine thanked for this post

  36. #36
    Cub Builder's Avatar
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    If you're working in a shop, it's pretty easy to do this with air pressure from your compression tester rather than rope, but either will work. With rope you don't have to worry about the prop whacking you.

    -Cub Builder

  37. #37
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    Executed rope trick today for a stuck valve. Reamed. Grateful to be back in business until OH this winter.


    Sent from my iPhone using SuperCub.Org
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    I recently had a valve issue on the RANS's Rotax. 20 over 85! When I took the head to "my" mechanic, He turned it upside down, squirted some brake cleaner, or maybe it was carb cleaner, (not important what it was, something he had handy and that stayed in a fluid state for a bit) and when it ran out the intake valve, the mystery was solved. He popped the valve out, and discovered the factory in Austria had missed a step, the valve seat wasn't ground [down deep enough. So, little sealing area, thus the leak. With no damage to the valve, he quickly ground the seat down to the correct depth and angle, put the valve back in, did the leak test, and I was good to go. Total elapsed time, both of us BSing the entire time, was 20 minutes. it was worth the 4 hour drive (1 way) to Elko, got it fixed plus got educated. Hal Stockman, mechanic virtuoso!
    Likes 40m, 180Marty, cubscout, motosix liked this post

  39. #39

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    Hal could be the replacement for this dude as the second most interesting guy in the world
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    Hal may also be the nicest
    Likes Kid Durango, jprax liked this post

  40. #40
    courierguy's Avatar
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    A thing I've noticed: is every heavy equipment .mechanic ( Hal's day job is fixing giant mining equipment, and he is highly respected and sought after in that field) I have run across are physically unimposing guys. Shorter and lighter than average is what I mean, the wizard that fixes my crane can't weigh 130 pounds, but is tough as nails and knows his biz like no one else in my area. Could be a coincidence, or some deep physocological thing, but get those guys around the biggest equipment made and stay out of their way, they get it done!
    Thanks mydoghasa170 thanked for this post

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