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  1. #1
    speedracerntrixie's Avatar
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    Bearing replacement help. Ralph, Bill??

    I had a major brain fart and tweaked the wrong needle on a 150cc twin. The result was it got hot enough to quit in flight. 6 flights later it has rod knock. I have it apart and really can't see any damage but I'm fairly sure the rod bearings are shot. My question is can the crank be pulled apart and the lower rod bearings replaced and the crank pressed back together or is the engine scrap? This is an EVO 150 not to be confused with Evolution and parts are not available so if this requires a new crank it's headed for the garbage can. Thanks guys for the replies.

  2. #2

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    Do you have Ralph's DIrect email address? If not, PM me, and I will send it to you. You can google it too.

  3. #3
    All Day Dan's Avatar
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    Ask Bill Jensen. Dan.
    wbilljensen@gmail.com
    Dan

  4. #4
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    If you can get new bearings the answer is yes the crank can be pressed apart and new bearings and pins installed then pressed together and realigned. The bearings may have a number on the side ,but of course the crank has to be taken apart before a person can see them.
    If you can\'\'t fix it with a hammer, you\'\'ve got an electrical problem.

  5. #5
    speedracerntrixie's Avatar
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    That's pretty much what I understood.. I have the engine apart and can see no obvious evidence that the bearings are bad. There is no real vertical play in any of the bearings and very little rock, and no discoloration of the bearing needles. The engine was designed so that the connecting rods can float laterally quite a bit. I'm measuring and the total lateral movement is close to .125. The bearings simply can't account for what I was hearing but the lateral movement can. I'm wondering if that is what I was hearing? While running the engine sounded normal. is it possible that the lateral movement of the connecting rods can produce a clicking noise? I'm hoping someone can answer that question before I bolt the engine back together. I am trying to make an IMAC contest next weekend so this has to be sorted out by Monday.

  6. #6
    Did the engine seize or just quit from being lean? If it over heated you should have piston failure before the bearing failure. The side clearance should not make noise unless something is bent. Such as a rod or wrist pin. But I am mostly guessing , pics would help with the guesses .
    Last edited by KenLambert; 07-24-2014 at 06:08 PM.
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  7. #7
    speedracerntrixie's Avatar
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    Thanks for the reply Ken. I can't see any damage at all. The pistons have a little blow by that I think is from the one lean run. I did let it cool down for an hour afterwards and put in 3 flights following the dead stick and she ran fine. The only change I had made was to switch from 40:1 to 50:1 as it had been run with 40:1 for 5 gallons. At this point I'm thinking about putting in back together, adding enough oil to being me back up to 40:1 and giving it another shot. If you look at the pics you will notice no discoloration of the needle bearings.
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  8. #8
    acerc's Avatar
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    Holding the base of the rod to one side of the crank can the rod rock on the bearing? Not sure but in the first pic it looks as though the gap between the rod and crank is different.
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    Last edited by acerc; 07-24-2014 at 07:12 PM.
    Robert
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  9. #9

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    Speedracer, nothing in your photos looks that bad. The wristpin spacers in the pistons will control any side movement of the rods. The skirt staining happened over time and not just on one run. I'm thinking any sounds you are getting from the engine is from lack of a normal lube film on the parts caused by the lean run. 2 stoke engines depend on a fairly heavy deposit of viscous oil between the parts during normal operation. This stays there unless the engine is run lean then high temperatures evaporate it or burn it off. Run this way too long and you get scored parts which I see no signs of in your photos. If this was my engine, I'd reassemble it and run it some more to see what develops. I know you know engines well enough to know if there are any bad bearings and you indicate they are ok. Other than some blow by staining, the piston skirts look good too. I think you have quite a bit more life left in that engine.

  10. #10
    speedracerntrixie's Avatar
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    Thanks Truck. All the bearings rotate freely. With no damage. The engine only has a couple hours run time and has been run rich enough for me to have to blow it out at full throttle before a take off roll. After 5 gallons I thought it was time to optimize the mixture and move away from the break in fuel. At this point my plan is to bolt it back together and run it. Bad news is I have to hand cut gaskets first.

    Ace, the connecting rods have sone lateral play. The picture that you posted with the arrows do illustrate this. The play is about .030. The engine was designed this way. I was considering adding some shims to the upper end to limit this but I would think if it was an issue I would have had a failure way before now. I'm thinking the best route to do at this point is put it back together and go back to 40:1.

  11. #11
    I would put a new set of rings ,that much blow by I would think they are worn or lost tension from heat. I have engines 10 years old and never had any oil other than synthetic at 40:1 then 50:1 and none have that blow by on the pistons.
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  12. #12
    CK1's Avatar
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    I would think that the "clicking" is from a lack of a film coating of lubricant sufficient enough to dampen stack up tolerances in the bearings . The blackened areas on the pistons are most likely from some ring leakage but primarily from oil flash of from the high temps. I would lube everything up well and reassemble and the clicking will probably diminish significantly . I would use 30:1 or 40:1 oil ratio for a while with proper tuning to get engine temps down.
    \"Aint this great !!\" - Chris
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  13. #13
    speedracerntrixie's Avatar
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    Quote Originally Posted by KenLambert View Post
    I would put a new set of rings ,that much blow by I would think they are worn or lost tension from heat. I have engines 10 years old and never had any oil other than synthetic at 40:1 then 50:1 and none have that blow by on the pistons.
    The rings look good. They moved freely in the piston groove and have no discoloration. I'm really leaning toward just pushing the engine a bit too hard too soon. I'm going to go back to 40:1 and I'm thinking about changing oil brands. I have been using Lucas semi synthetic.

  14. #14

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    Regarding the residue on the piston skirts, many times this accumulates during the initial break in process. Push an engine too hard too early and add a bit of extra heat and you will get this. It really doesn't hurt anything as long as it doesn't get any worse. My bet is if you clean the piston skirts before reassembly, even reusing the original rings (if they sealed well) this won't recur. Skirt staining is a good indicator of the engine's history though.

  15. #15
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    You haven't considered the tension of the rings, which may have been significantly lowered from a hot lean run. Also, and equally important is the ring gap. It should be .003 to .005". The blow by staining indicates to me that the rings definitely were not sealing well. I would add new Bowman rings for sure. What's 22 bucks to make your engine run better and last longer, especially since you have it apart now anyway?

    Before re-assembly with new rings, I would take some Scotchbrite and acetone or carb cleaner spray and clean those pistons up. Lots of people like to use synthetic from the start nowadays, but I'm still an old fashioned fan of using dino oil for break in.... Why delay the all important break in by running synthetic oil and risking glazing the cylinders and never getting a good ring seal?

    AV8TOR
    Last edited by av8tor1977; 07-24-2014 at 10:33 PM.
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  16. #16
    av8tor1977's Avatar
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    Yep, just studied the pic again. Two things would hit the trash can if it were mine. The rings, and the oil I had been using.....

    AV8TOR
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  17. #17
    speedracerntrixie's Avatar
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    Quote Originally Posted by av8tor1977 View Post
    You haven't considered the tension of the rings, which may have been significantly lowered from a hot lean run. Also, and equally important is the ring gap. It should be .003 to .005". The blow by staining indicates to me that the rings definitely were not sealing well. I would add new Bowman rings for sure. What's 22 bucks to make your engine run better and last longer, especially since you have it apart now anyway?

    Before re-assembly with new rings, I would take some Scotchbrite and acetone or carb cleaner spray and clean those pistons up. Lots of people like to use synthetic from the start nowadays, but I'm still an old fashioned fan of using dino oil for break in.... Why delay the all important break in by running synthetic oil and risking glazing the cylinders and never getting a good ring seal?

    AV8TOR
    As I said early on, the goal is to get it up and running for a contest in 8 days from now. There is no way to send Frank a piston and cylinder and have him custom cut me a set of rings and get them run in and be able to make the contest. Let alone having him do a one off set for only 22 bucks. My intuition is telling me that I just pushed the engine a bit too hard before the rings got fully seated. Remember it only has 5 gallons through it. That was enough for the DA 150 engines I have had but maybe not enough on this particular engine. That may sound like a lot of fuel but this airplane carries 1/2 gallon. The cylinder bores still have good cross hatch pattern to them as well. I would tend to agree that the rings may not be sealing as well as I would like them to but I think it's because they are still relatively new and not damaged. Give me a day or two and I will publish an update. I do appreciate the feedback though.

  18. #18

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    Speed:
    Was wondering if you checked the piston wrist pins that connect to the connecting rods. Are they on bearings on plain bushings? The crank bearing is a needle bearing type correct? As long as those bearings rotate freely, those are probably fine. I wonder if the piston wrist pin bushings have some play in them?

    Just asking, hope all is fine.

    Glenn
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  19. #19
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    I agree with tossing the oil also, Lucas makes some very good items, but I do not like what I see here. Syn oil takes so much longer to seat the rings in on a new engine especially if it has hard rings. Myself I do a gallon of dino oil mix and then go to my Syn oil from then on.
    Frank can make the rings for you W/O the piston and cyl if you have access to some precision Measuring tools and give him whats needed for sizes.
    Everything else I have read here is about dead on to what my own thoughts are. I would put it together and run it and see how it pans out.
    Good Luck at the contest.
    If you can\'\'t fix it with a hammer, you\'\'ve got an electrical problem.

  20. #20

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    Quote Originally Posted by av8tor1977 View Post
    Yep, just studied the pic again. Two things would hit the trash can if it were mine. The rings, and the oil I had been using.....

    AV8TOR

    I agree with AV8TOR
    I never met a engine I did not like !

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  21. #21
    av8tor1977's Avatar
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    Quote Originally Posted by Cyberwolf View Post
    I agree with tossing the oil also, Lucas makes some very good items, but I do not like what I see here. Syn oil takes so much longer to seat the rings in on a new engine especially if it has hard rings. Myself I do a gallon of dino oil mix and then go to my Syn oil from then on.
    Frank can make the rings for you W/O the piston and cyl if you have access to some precision Measuring tools and give him whats needed for sizes.
    Everything else I have read here is about dead on to what my own thoughts are. I would put it together and run it and see how it pans out.
    Good Luck at the contest.
    Yes, I have had Frank Bowman make many rings from my measurements. He hesitates to do so, unless he knows you. Just tell him going in that you will guarantee your measurements or else hold him harmless if they don't fit just right. Once he learns to trust you, he will accept your measurements without hesitation. (If the rings are too wide, you can lap them on a piece of 400 sandpaper and glass, if the gap is too tight, you can file it until it fits.) If it were me, I would take very careful measurements of the ring I.D. (inside the cylinder), O.D. (Cylinder diameter), and width with micrometers. Then put the engine back together for this contest, run your favorite dino oil at 40:1, and in the meantime order in a set of Bowman rings for it. I have never seen nor heard of anyone that didn't have high praise for Frank's rings after once using them. It is a great upgrade for nearly any engine, but especially Chinese engines...

    AV8TOR
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  22. #22
    speedracerntrixie's Avatar
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    That actually sounds like a solid plan. I have heard nothing but good things about Franks rings. To the point that I am wanting to get one for the YS 115 that I race with. If I continue to have issues I will be pulling a cylinder and piston off and send them to him. In the meantime I need to find some Penzoil air cooled. Just to clarify if you are not familiar with the origin of this particular engine. It was manufactured in Spain. The company is well known for manufacturing racing cart engines and thought they would have a market in giant scale engines.

  23. #23
    av8tor1977's Avatar
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    Pennzoil makes a new oil called "Outdoor", but I don't know how good it is. They quit making the original "For Air Cooled" because the EPA kept outlawing or restricting (thus raising the price out of sight) the ingredients they wanted to use and they had to keep re-formulating the oil. I understand the same (or similar) oil is now made by Shell under the "Aerosport" name. Luckily I'm still working out of a large stock of the original "Air Cooled" oil that I had, but it is almost gone unfortunately.

    Good luck with the contest and your engine. I am sure it will hold together that long, but severe ring blow-by can cause the rings to eventually carbon up and stick, and/or overheat the piston skirt, burn the oil off, and cause seizures so keep an eye on it.

    AV8TOR
    Last edited by av8tor1977; 07-26-2014 at 03:23 PM.
    If it is not SCARY, it is NO WHERE NEAR powerful enough!!
    All R/C planes have expiration dates---> It's just not printed on them anywhere!

  24. #24
    All Day Dan's Avatar
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    Av8tor, I sent you a pm. Dan.
    Dan

  25. #25
    speedracerntrixie's Avatar
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    Quick update, I cleaned the pistons and heads. All needle bearings got a direct shot of 2 stoke oil as did the cylinder walls and rings. The engine is all back together and installed back into the airplane. When turning it over with the prop there is no clicking noise and it has just as much compression feel as any of my DA 150 engines did. I still need to hook up the plumbing and exhaust. That will have to wait another day, tomorrow I decided I'm going to take my old reliable Aurora out and de stress flying it. I hope to post a video of the run up on Monday.


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