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HelicopterEngines Plugs Mufflers Fuel › blew a hole in my 91HZ piston: cleaning procedure?
02-12-2018 06:27 PM  9 days agoPost 1
cudaboy_71

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sacramento, ca, u.s.

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Muffler worked loose last flight and went lean (I guess that's the culprit). Blew a hole in the piston. Doesn't seem to be any other damage after complete teardown.

Never done that before. What's the usual cleanup procedure? There's little bits of piston from a fine paste to coarse-salt-sized chunks throughout the crankcase, bearings, all over the crankshaft.

Soak in something --acetone, gasoline, some other solvent? and blow off??? I obviously want to make sure there's no grit left to make a mess after I rebuild.

thanks.

if it ain't broke, break it.

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02-12-2018 06:49 PM  9 days agoPost 2
ICUR1-2

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Ottawa, Ontario

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The repair cost, plus time, I Don't think I would rebuild incase I missed some metal fragments.
Of course if you have the time and the ability to clean it properly.

Got any pics of how bad it is.

spending time, paying attention

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02-12-2018 07:09 PM  9 days agoPost 3
cudaboy_71

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sacramento, ca, u.s.

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I've got an old parts motor. So, I have a piston. It actually has the matching sleeve and ring from when it was running. So, I'll probably keep the set matched. I had just got done rebuilding it with new bearings. But, when I fired it up I learned quickly I had bent the crank and just threw the whole thing in a box as a parts motor.

So, no out of pocket to rebuild. Just an hour or two of time.

I took the pics below right before cleaning. This motor looks to only have blown the piston. I just got done washing all the aluminum parts in water and blowing off and wiping down.

I soaked the bearings, crank, head, conrod and pin in oil, then blew off with air. They look to be fine as well.

How to 'clean properly' was the question. Think that's good enough?

if it ain't broke, break it.

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02-12-2018 07:11 PM  9 days agoPost 4
Flyin for Jesus

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Troy, IL. 62294

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I have an ultrasonic cleaner that I run everything through from guns to R/C.

Without that, certainly some carb cleaner with a straw and you can get it fully cleaned up. Just new bearings, seal, piston and ring. ( list not exhaustive )

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02-12-2018 07:14 PM  9 days agoPost 5
cudaboy_71

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sacramento, ca, u.s.

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I might have an ultrasonic cleaner somewhere. do you use different solutions for aluminum and iron motor parts?

if it ain't broke, break it.

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02-12-2018 07:20 PM  9 days agoPost 6
balsapro

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Gallatin,TN

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In an ultrasonic you could probably use the same cleaner but dont put different metals together... or the alum parts will change color

Build the Best, Fly the Best, Crash the Best

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02-13-2018 12:07 AM  9 days agoPost 7
heli4fun

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TRUMP, USA

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91Hz
How does the head look like?? Have a pic?
If it's pitted due to the metal pieces from the piston,i would not reuse that head,might/will affect compression then you'll be chasing tuning inconsistency...
Done that been there.

Ask me how I know!

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02-13-2018 12:11 AM  9 days agoPost 8
cudaboy_71

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sacramento, ca, u.s.

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It doesn’t look too bad. The one with the glow plug is the one that just blew the piston. The one without is my parts motor head. It ran fine up until I bent the crank on impact

if it ain't broke, break it.

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02-13-2018 12:41 AM  9 days agoPost 9
JuanRodriguez

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The Villages, Florida

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FWIW, I don't think you're blown piston was caused by a loose muffler..... more than likely, lean running motor due to tuning...... just MHO.....ask me how I know .....

Been there, done that and old enough to know better.....

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02-13-2018 12:47 AM  9 days agoPost 10
cudaboy_71

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sacramento, ca, u.s.

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Ya. I suck at tuning. But I had a gallon through it last week at 65°F and it was running decently. This past Sunday it was 45°F and I only leaned it 2 clicks on high and one on mid and it seemed to be liking it. But with 30 seconds left in the 2nd tank of the day “pop”. It’s not a nice sound. *shrug*

I’ll probably replumb the line again anyway just to be sure.

if it ain't broke, break it.

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02-13-2018 01:26 AM  9 days agoPost 11
JuanRodriguez

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The Villages, Florida

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cudaboy_71
Ya. I suck at tuning. But I had a gallon through it last week at 65°F and it was running decently.
That really doesn't matter..... I speak from experience (bad one at that)

Years ago I received a Quick 50 Pro from Irvin @ Quick WW to do a review on the kit...... I installed an OS 50 for a power plant..... As a side note, Curtis Y flew this machine during one of his appearances at one of our fun flys in Rochester, NY. I'm sure I can find and post the video if anyone is really interested....

Long story short, I was plagued with some lean runs on that machine and could not figure out what was going on.....It would fly great one flight and run lean on the next.....

Fast forward.........the fuel line clunk furnished with the kit was proven defective..... during the manufacturing process, there was a piece of metal left inside the clunk that would flap partially shut at times and completely open at other times..... Hard to believe that could happen but it did....

I give credit to my flying buddy, Al Magaloff, for discovering that piece of metal in the clunk !

End result..... several lean runs leading up to that "pop" !! Sure enough, a hole through the top of the piston exactly the same as yours......

I can't definitively tell you how much fuel was run through the motor before the piston incident other than probably several gallons......

Been there, done that and old enough to know better.....

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02-13-2018 01:44 AM  9 days agoPost 12
heli4fun

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TRUMP, USA

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91Hz
Yeah,I know that all too familiar sound of...."Pop"!!! It's happened to me a couple of times unfortunately.
Once from a loose muffler,another time from a clunk line that has been flown one too many times and i neglected changing it out.
By the looks of your pics of the two heads,they both look good.
A couple of clicks (from my experience in the past) shouldn't have made it run lean.I too ran the OS 91HZ through muffler pressure, my high needle would be just under (a few clicks) 1 and half turns out and the mid was 1 and 3/4 out.I live in San Francisco and notice you live in the Petaluma area,our temp/humidity variables should be pretty much similar since we're only 35-40 miles apart.I don't know how long you've been flying nitro,but you have to have an ear for it (with enough experience) when that engine is:
Unhappy
Running Lean
Gurgling (too rich)
I don't go by visual smoke only,but by sound/performance/temp.
After landing,I immediately (check the "CULO") check right under the bottom plate for temp changes which can be a telltale sign of the engine having a ..."Bad day"
In the end,our experiences good or bad is a lesson learned.
I'm mostly electric now piro tic tocs are easier with electric,but my roots are nitro from back in the day.
I was contemplating on coming up there to Petaluma one day to experience a different field.

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02-13-2018 02:52 AM  9 days agoPost 13
cudaboy_71

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sacramento, ca, u.s.

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I’m gonna bet the farm (my engine again) that it was the loose muffler. Too much of a coincidence to be anything else. I think I just lost fuel pressure and it leaned out.

I’m running an old GP exhaust pipe that always made great power. But, it has a tapped header section that I never trusted—and now it has cost me. I just ordered some 5mm longer bolts and some nord-lock washers to lock down some nuts. That thing won’t come loose again now

if it ain't broke, break it.

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02-13-2018 08:40 AM  8 days agoPost 14
ICUR1-2

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Ottawa, Ontario

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cudaboy_71
Ya. I suck at tuning. But I had a gallon through it last week at 65°F and it was running decently. This past Sunday it was 45°F and I only leaned it 2 clicks on high and one on mid and it seemed to be liking it. But with 30 seconds left in the 2nd tank of the day “pop”. It’s not a nice sound. *shrug*
You're suppose go richer when it's colder ... plus if the pipe comes loose it will also cause it to lean out even more.. At least the mystery of how it happened is clear now.

spending time, paying attention

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02-13-2018 01:52 PM  8 days agoPost 15
cudaboy_71

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sacramento, ca, u.s.

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ICUR1-2
You're suppose go richer when it's colder ...
Heh. I do know that. But, now you have me second guessing myself. I’m thinking I just typed that wrong. But now I’m wondering if I really did lean it :-o if I did, I guess that answers that question.

if it ain't broke, break it.

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02-13-2018 07:35 PM  8 days agoPost 16
ICUR1-2

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Ottawa, Ontario

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the mind plays funny games when it comes to memory .

spending time, paying attention

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HelicopterEngines Plugs Mufflers Fuel › blew a hole in my 91HZ piston: cleaning procedure?
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