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Carbon Cub Rough Running Engine

That video sounds more like a fuel related problem. Most intermittent ignition problems that have enough fuel in the system have a backfire when the spark is re added to the excess rich mixture?

Glenn
 
Maybe check the o rings on the induction tube. If I remember right they are o rings instead of paper gaskets where they attach to the cyl


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The tach variation exceeds what I've ever seen from a fuel or induction issue. That looks electrical to me. Like a short or a loss of ground.
 
It sounds like lack of fuel to me also.
Can you spray starting fluid into the carb to see if the RPM picks up?
(without getting chopped to bits, I mean.......)

As a Yamaha motorcycle mechanic in the 80's we used an Allen Test and later a Sun Exhaust Gas Analyzer on the 4-strokes.
It read CO's (burned carbons) and HC's (unburied hydrocarbons).

A lean misfire would have low CO's (burned fuel) and High HC's because it was getting little fuel which caused a misfire and the unburied fuel showed up as HC's. We'd spray Berryman's carb cleaner or WD40 at the intake manifolds and if the CO's picked up we knew they were leaking. If not, we'd spray it into the intake. If the CO's picked up we knew there was a lean mixture. (Sadly, both Berryman's and WD40 were neutered a decade or 2 ago and no longer work as a starting fluid. And lighter fluid no longer works for tennis ball cannons :(

A rich Mixture would show high CO and high HC.

An ignition misfire would show no CO's but very high HC's.

I have not seen an analyzer like this at an FBO, but I just did a search for "Portable Exhaust Gas Analyzer" and there are a bunch of them on the market.

We also used an in-line spark checker frequently. It provides a gap where you can watch the spark jump inside a clear plastic housing, or watch it fail. You can increase the gap by twisting the housing to the point where the spark can't jump it.

As an aside, I chased a similar issue on my snowblower for a few seasons. When under a big load it would suddenly die. I was sure it was an ignition issue because it cut off without warning, but ultimately discovered that it had a non-vented gas cap on it from another model. The vented gas cap from my lawnmower solved the problem with a twist of the wrist.
 
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Does it have fuel flow?
Start simple. Vent lines plugged?
If you take the supply line off, how many gallons do you get in 1-2-3 minutes?
 
If it was an electric power issue, I believe you would lose your tach signal. As it was cutting out, you still showed green LED's and numbers on the screen.

Web
 
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.
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You can see the water droplets in thispicture from running on the ground and not getting up to temp.
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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.
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You can see the water droplets in thispicture from running on the ground and not getting up to temp.
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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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Wow, in all the exhaust valves I've had or seen burnt / cracked I've never seen the intake valve head give up.
 
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?
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.
 
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
 
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! :p:p
 
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Steve

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

http://forum.cubcrafters.com/showthread.php/2582-Titan-engine-problem?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, 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.
 
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.
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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.
 
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
 
Be easier to see what is happening now.
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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, 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.
 
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
 
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