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Thread: Carbon Cub Rough Running Engine

  1. #41

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    Quote Originally Posted by Steve Pierce View Post
    After last nights engine run and no change in engine rpm when going through each ignition system i conclude it had to be somethong other than ignition. In the air it sounded like a back fire. When I pulled it through last night I had a soft cylinder. In December during the condition inspection #4 was 70/80 leaking out the intake while everything else was 76/80 or better. Eddie brought my 14MM test hose today so checked compression on #4 and it was 10/80. Borescope didn't show anything that I could see and staking did no good so against everything I have ever read Mike Busch write I pulled the cylinder. Intake valve burnt pretty good. Gonna put an Electronics International CGR30P in while we have everything apart. You can see the water droplets in the second picture from running on the ground and not getting up to temp.
    Attachment 36519
    You can see the water droplets in thispicture from running on the ground and not getting up to temp.
    Attachment 36520

    Attachment 36521

    Attachment 36522

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    Yup. Blowing fire back up the intake is what it sounded like. Glad thats it. Do you think the valve might have been snugged a but too tight??..wasnt that cylinder s but soft at annual?


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  2. #42
    irishfield's Avatar
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    Wow, in all the exhaust valves I've had or seen burnt / cracked I've never seen the intake valve head give up.

  3. #43
    PerryB's Avatar
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    Yeah, that's a unicorn. Maybe it got a chunk of carbon under it or something along those lines.
    After Monday and Tuesday, even the calendar says WTF !

  4. #44

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    Quote Originally Posted by PerryB View Post
    Yeah, that's a unicorn. Maybe it got a chunk of carbon under it or something along those lines.

    or did the ignition cause it?

  5. #45
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    Quote Originally Posted by tempdoug View Post
    or did the ignition cause it?
    I'm having a hard time connecting those dots, unless it was producing an erroneous spark during the intake stroke on that cyl. and then it would have had one b**ch of an induction backfire. Probably enough to prevent even getting it started. Upon re-think I'm veering away from the carbon theory. I think a piece of the valve rim/margin chipped off and started the degeneration process.
    After Monday and Tuesday, even the calendar says WTF !

  6. #46
    cubdriver2's Avatar
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    Interested to see if the valve is the real problem. Not convinced just being burnt would cause what was happening. If it was hanging open it would act as a decompression release/jakebrake and a power loss by recirculating air?

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  7. #47
    Scouter's Avatar
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    Steve

    This one was in Maine just over the hill from me
    Push rod clearance
    Jim

    http://forum.cubcrafters.com/showthr...highlight=jake
    Last edited by Scouter; 04-20-2018 at 12:45 AM.
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  8. #48
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    Quote Originally Posted by RaisedByWolves View Post
    What’s Jon at cubcrafters have to say?


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    Might check intake or exhaust valves for damage.


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  9. #49
    Gordon Misch's Avatar
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    Sticky valve stem, or ill-seated valve. In any case, Eddie has a good mech.

    I had a fussy Wisconsin engine on my baler that would sputter and pop and essentially cut out, then always start up again. I never took it apart, but I suspected a too-tight intake valve stem/guide.

    Copped out and am using a tractor with PTO now, instead of a team of horses. Embarrassing. Apologies to Amos and Sandy (my team of Shires). They still pull the manure spreader though - - - Like politicians, spreading their own s...... SJ, don't ya dare kill the thread on this!
    Last edited by Gordon Misch; 04-20-2018 at 01:28 AM.
    Gordon

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    My SPOT: tinyurl.com/N4328M (case sensitive)
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  10. #50
    Steve Pierce's Avatar
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    Quote Originally Posted by Scouter View Post
    Steve

    This one was in Maine just over the hill from me
    Push rod clearance
    Jim

    http://forum.cubcrafters.com/showthr...highlight=jake
    Thanks Jim, exactly the same issue and cylinder except I think we have excessive valve clearance as I was able to remove the rocker shaft with my fingers.

    I did not measure the valve guide but felt normal. I have an airplane to finish building so I sent the cylinder to the cylinder shop for repairs.
    Steve Pierce

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    Will Rogers

  11. #51
    skywagon8a's Avatar
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    Steve, While the cylinder is off look inside at the lifter. Look around for any indications of small pieces of metal hitting the crankcase. Years ago I had the mushroom on an intake valve lifter break causing the valve to remain open. The engine quit with no warning over inhospitable terrain in a snow flurry. Then after what seemed like forever it started and ran fine for a few minutes until I just happened to be over an airport when it quit again. All indications were the same as you have found except that there wasn't any rough running. It just quit. In an effort to get it home, I pulled the cylinder, lapped the valve, and in the process of reinstalling the cylinder I spotted some strange marks inside the case. The mushroom on the lifter was broken and jammed into the case. Needless to say a major overhaul was done.
    N1PA

  12. #52
    Steve Pierce's Avatar
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    Got the cylinder back from having new exhaust guide, intake and exhaust valves and seats ground along with new valve springs. Seems the exhaust valve inner spring was broken and my cylinder guy has seen a lot of those on the ECI cylinders. Ran it up this morning and all is normal.
    Click image for larger version. 

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    Steve Pierce

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    Will Rogers
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  13. #53
    Eddie Foy's Avatar
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    If it was I, I would install a complete new set of springs.
    "Put out my hand and touched the face of God!"

  14. #54
    www.SkupTech.com mike mcs repair's Avatar
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    this is a neat video on valve operation...

    https://www.facebook.com/EngineLabs/...5369096479973/

  15. #55
    Eddie Foy's Avatar
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    Helluva difference between 2500 RPM in a Lycoming and 9000 in a Nascar engine. They will actually put a new set of springs in right before a race.
    "Put out my hand and touched the face of God!"
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  16. #56
    cubdriver2's Avatar
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    Quote Originally Posted by Eddie Foy View Post
    Helluva difference between 2500 RPM in a Lycoming and 9000 in a Nascar engine. They will actually put a new set of springs in right before a race.
    Back in the 70s I had a 302 Z28, that was 60 over with 12 to 1 pistons, 513 rear. 8k was my shift point, went past 9k when I missed a gear. Solid lifters, adjusted valves lash less then 6 times in 30,000 miles before I sold it. My foot was in it every time I was in the seat.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"

  17. #57
    Steve Pierce's Avatar
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    Be easier to see what is happening now.
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    Steve Pierce

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  18. #58
    Steve Pierce's Avatar
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    A little update on this burnt intake valve. The owner talked to Bobby Looper (Titan Product Support Engineer) at v Oshkosh. We already knew that ECI spec'd the O-340 for an MA4-5 carb but that carb wouldn't fit under Cub Crafters cowl so they went with the 10-3678-32 carb like the 160 hp O-320 and changed the throat in the induction and added the peppered fuel nozzle. Bobby says the there is not a jet big enough for this carb and is suppose to send us the drill size to get enough fuel flow on take-off. He also said the old school method of leaning until the engine stumbles and then enriching a bit does not work with electronic ignition. The electronic ignition has a hot enough spark to run smooth with a lean mixture which is how the owner had been leaning it. Said we needed to see 1200 degree EGT'S on take-off and we are seeing 1300-1350.

    To add to this I got a call from cubdrvr on Friday. They had been troubleshooting aN RV with a Light speed ignition on one side and mag on the other. Ran rough on the mag but fine on the electronic ignition. They installed another mag and harness and removed the P-lead with no change. Found an intake leak and problem loved which reinforced the info on the electronic ignition having a hotter spark and able to fire a leaner mixture.

    Thought others might find this info interesting and useful.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  19. #59
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    Steve, many years ago I had a truck with a hopped up 460 and an Accel dual point distributor. When I removed that system and installed an MSD, it nearly eliminated the need for choke in the morning. The friend who talked me into the MSD system told me this would happen, and of course I thought he was full of it.
    After Monday and Tuesday, even the calendar says WTF !

  20. #60
    Scouter's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    A little update on this burnt intake valve. The owner talked to Bobby Looper (Titan Product Support Engineer) at v Oshkosh. We already knew that ECI spec'd the O-340 for an MA4-5 carb but that carb wouldn't fit under Cub Crafters cowl so they went with the 10-3678-32 carb like the 160 hp O-320 and changed the throat in the induction and added the peppered fuel nozzle. Bobby says the there is not a jet big enough for this carb and is suppose to send us the drill size to get enough fuel flow on take-off. He also said the old school method of leaning until the engine stumbles and then enriching a bit does not work with electronic ignition. The electronic ignition has a hot enough spark to run smooth with a lean mixture which is how the owner had been leaning it. Said we needed to see 1200 degree EGT'S on take-off and we are seeing 1300-1350.

    To add to this I got a call from cubdrvr on Friday. They had been troubleshooting aN RV with a Light speed ignition on one side and mag on the other. Ran rough on the mag but fine on the electronic ignition. They installed another mag and harness and removed the P-lead with no change. Found an intake leak and problem loved which reinforced the info on the electronic ignition having a hotter spark and able to fire a leaner mixture.

    Thought others might find this info interesting and useful.


    Steve can you take a few pix and document this? would be interested to check my carb when you get it figured out.

    Jim

  21. #61
    www.SkupTech.com mike mcs repair's Avatar
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    Carbon Cub Rough Running Engine

    Neat thread. I hadn’t read all of it before. Just goes to show what a sticking open(or clinker under it) intake valve will do to you. You don’t just loose that cylinders output power, you loose at least the next cylinders fuel charge and power too, since intake system is pressurized at that point instead of vacuuming


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  22. #62
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    Quote Originally Posted by Steve Pierce View Post
    ….He also said the old school method of leaning until the engine stumbles and then enriching a bit does not work with electronic ignition. The electronic ignition has a hot enough spark to run smooth with a lean mixture which is how the owner had been leaning it....
    Reminds me of a guy I used to know.
    He said he switched to one mag, leaned until just barely rough, then switched back to both and called it good.
    I wonder if that would work with the dual electronic ignition?
    Cessna Skywagon-- accept no substitute!

  23. #63
    PerryB's Avatar
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    We have a local/older/high-time pilot here that does the same thing.
    After Monday and Tuesday, even the calendar says WTF !

  24. #64
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    We just put the 4-5 carb on the 0-340 we installed on my supercub. Can not go full rich, full throttle on take off without it running very rough. (acts like its getting way to much gas) We have to lean about 3/4" travel on the mixture. My fuel flow gauge shows this to be about 13-14gph. At no time have I ever been able to get the 15-16gph fuel burn without the engine running rough and stumbling. My CHT are around 325-375 but the #2 cylinder EGT is high. I have to work at it to keep it below 1400. The others in cruise are around 1200. After reading this thread I may be leaning it to much my self. I am running a Vetterman exhaust which I think was designed for the 150hp engine and wondered if that was a factor. At 30 hours and working out the bugs. (with a smile)

  25. #65
    Steve Pierce's Avatar
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    Quote Originally Posted by j5mike View Post
    We just put the 4-5 carb on the 0-340 we installed on my supercub. Can not go full rich, full throttle on take off without it running very rough. (acts like its getting way to much gas) We have to lean about 3/4" travel on the mixture. My fuel flow gauge shows this to be about 13-14gph. At no time have I ever been able to get the 15-16gph fuel burn without the engine running rough and stumbling. My CHT are around 325-375 but the #2 cylinder EGT is high. I have to work at it to keep it below 1400. The others in cruise are around 1200. After reading this thread I may be leaning it to much my self. I am running a Vetterman exhaust which I think was designed for the 150hp engine and wondered if that was a factor. At 30 hours and working out the bugs. (with a smile)
    Joe with the Super Legend might can help. He changed his carburetor and has now gone to fuel injection.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  26. #66

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    J5Mike, the exhaust systems for 320s and 360s are basically the same. The 360 is 1.8 inches wider than the 360. I designed most popular system which was the 360 crossover and placed a cutoff mark on pipes 1 and 2 if it was going on a 320. Vetterman
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  27. #67
    Steve Pierce's Avatar
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    Quote Originally Posted by Scouter View Post
    Steve can you take a few pix and document this? would be interested to check my carb when you get it figured out.

    Jim
    Will do Jim.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  28. #68
    AdirondackCub's Avatar
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    Steve had one local with some EXTREME fouled plugs. Assume you checked this but it solved our issue locally.

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