As the title states, what are the symptoms of a blown out or sucked in cylinder gasket? I've heard it typically manifests itself once the engine is up to temp. I have a 157 that I think might be exhibiting this issue, but I'd like to hear the symptoms and see if aligns with what I'm experiencing. I know the issue I'm having is not ignition related.

Does the engine seem low on power? That is what caused me to think something was wrong with mine. It went from destroying the 3W 3D prop to not even ripping it at all. I could visibly see the gasket sucked in on the front of the cylinder.

Here's a quick recap of what I'm experiencing (this recently just started happening) -- engine starts and runs absolutely perfectly. Idle, to WOT and everything in between. A few minutes into a flight it will start to to sputter, cough, miss and make all kinds of terrible sounds, almost like a rev-limiter at just under 1/2 throttle and above. Idle to just under half it runs absolutely perfectly; absolutely zero indication of a problem, no deadsticks, will happily fly/run through a tank. Half and above it pops, stutters, etc... and doesn't seem to get better or worse. No amount of tuning -- pig rich to lean and everything in between seems to make zero difference. Seems to be a little worse in flight then on the ground, but that's hard to judge. Oddly enough, when it's acting up, sometimes if I let the engine idle (on the ground, obviously) for 20-30 seconds and then advance to WOT, it will run great for a few seconds before it starts acting up again. I tried 2 different known-good 3W ignitions and now a CH ignition all with the exact same symptoms. Pretty much rules out ignition...

Any chance the hub may have slipped?

I doubt it and here's why -- The TDC mark on the hub still aligns with the mark on the case. I just re-timed the engine for the CH ignition and this was going on prior to. Assuming that's a valid indication that the hub has not slipped?

On standard mufflers right now, BTW.

Also running the aluminum reed block.

did you contact gerhardt at Aircraft International and ask him....

it sounds like maybe it could be a heat related issue (sorry.. obvious huh?)
but it could also be the gasket under the reed cage or between that block and the case....
do you have the plastic base under the carb??? it may be warping... you can take it off and sand/grind it flat and use Honda-Bond (or other petrolium safe gasket sealer) to reassemble with.....

see the grey stuff between the carb and the plastic base... http://www.giantcircus.com/WWW_For_Sale/DSC02733.htm

and the other gasket between the case and the alu reed block is narrow also...

is there a lot of fuel spray in and around the motor??

Call Gerhardt... he will help you troubleshoot it.

I would do as mith suggested and also reseal the entire engine. Does yours have a split case?

I haven't talked to Gerhard.. ...yet.

The reed and carb assembly is sealed well (or at least was) with ultra copper. Engine and carb area are all dry. I'm going to pull the cowl and check it all out again, though.

Could this be carb related? I don't see how, but it started a few flying sessions after installing a Walbro carb. I got lazy when I moved the engine into a new airframe and didn't want to re-engineer the throttle linkage, so I used the original Walbro that I had replaced with a Tillotson (prefer the Till) due to the throttle arm...

My da was just doing this and I resealled the reed block to the engine and all is well.

As requested, pics of the front of the base gaskets -- Does this one looked sucked in?







Looks like the top of the engine has a slight amount of dampness at the case seam -- the rest is completely dry:

The right cylinder looks fine (looking from the front), the left one hard to tell, can you see any gasket sticking out or flush with the front, or does it appear to have a gap?

Try the Tillitson again, Abram......... The 157 CSTS I'm running has a miss in it. I think I may have found it. I'll know once I get the ignition I just bought from you, and a new set of plugs. Was running 1 ignition for about the past 30 flights, and had a miss on the front set of plugs. Moved the ignition to the rear set of plugs, and added one from my 106. Long story short, front set of plugs missed with 2 diff ign's on them, and rear set, in which hasn't seen fire in probably 2 years run AWESOME!!!

BTW- I'm running the plastic reed housing and carb block.

Chris~

Glad you found the prb Chris ! Guys I have also in the past found air leaks at the cylinders and carbs by running the engine and spraying those areas with carb and choke cleaner. It will make the engine stumble . Then you know there is a leak.

I probably shouldn't be able to do this, right?









Looks sucked in: