RunRyder RC
 7  Topic Subscribe
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 492 views POST REPLY
HelicopterEngines Plugs Mufflers Fuel › blew a hole in my 91HZ piston: cleaning procedure?
02-12-2018 06:27 PM  66 days agoPost 1
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-12-2018 06:49 PM  66 days agoPost 2
ICUR1-2

rrElite Veteran

Ottawa, Ontario

My Posts: All  Forum  Topic

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

PM  EMAIL  GALLERY  Attn:RR  Quote
02-12-2018 07:09 PM  66 days agoPost 3
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-12-2018 07:11 PM  66 days agoPost 4
Flyin for Jesus

rrVeteran

Troy, IL. 62294

My Posts: All  Forum  Topic

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 )

PM  EMAIL  GALLERY  Attn:RR  Quote
02-12-2018 07:14 PM  66 days agoPost 5
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-12-2018 07:20 PM  66 days agoPost 6
balsapro

rrVeteran

Gallatin,TN

My Posts: All  Forum  Topic

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

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-13-2018 12:07 AM  65 days agoPost 7
heli4fun

rrNovice

TRUMP, USA

My Posts: All  Forum  Topic

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!

PM  EMAIL  GALLERY  Attn:RR  Quote
02-13-2018 12:11 AM  65 days agoPost 8
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-13-2018 12:41 AM  65 days agoPost 9
JuanRodriguez

rrProfessor

The Villages, Florida

My Posts: All  Forum  Topic

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.....

PM  EMAIL  GALLERY  Attn:RR  Quote
02-13-2018 12:47 AM  65 days agoPost 10
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-13-2018 01:26 AM  65 days agoPost 11
JuanRodriguez

rrProfessor

The Villages, Florida

My Posts: All  Forum  Topic

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.....

PM  EMAIL  GALLERY  Attn:RR  Quote
02-13-2018 01:44 AM  65 days agoPost 12
heli4fun

rrNovice

TRUMP, USA

My Posts: All  Forum  Topic

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.

PM  EMAIL  GALLERY  Attn:RR  Quote
02-13-2018 02:52 AM  65 days agoPost 13
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-13-2018 08:40 AM  65 days agoPost 14
ICUR1-2

rrElite Veteran

Ottawa, Ontario

My Posts: All  Forum  Topic

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

PM  EMAIL  GALLERY  Attn:RR  Quote
02-13-2018 01:52 PM  65 days agoPost 15
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

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.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-13-2018 07:35 PM  65 days agoPost 16
ICUR1-2

rrElite Veteran

Ottawa, Ontario

My Posts: All  Forum  Topic

the mind plays funny games when it comes to memory .

spending time, paying attention

PM  EMAIL  GALLERY  Attn:RR  Quote
02-23-2018 09:08 PM  55 days agoPost 17
GeezerJoe

rrNewbie

Kernersville, NC USA

My Posts: All  Forum  Topic

Sounds like good advise has been offered on the cleaning question.

I'm really curious about what appears to be serious pitting in the sidewalls near the intake porting and under where the cylinder liner goes.
I just replaced the rear bearing and conrod in my .91 and the inside didn't have any pitting at all.
Could that be from something corrosive left in the engine? Maybe?

Also, the piston and head on all of mine have always had a dark brownish copper look even on my oldest engine which has about 150 hours on it.
I've never seen a ringed engine with what looks like carbon build-up.
I did have an old used ABC engine I used on an airplane, it had over 200 hours on it and had that black carbon look. I just never noticed a ringed engine that black before.

I'm just curious, I may be running mine too rich? but I'm getting right at 8 minutes per tank on 30%. I've had it lean enough to get that pinging sound (pre-ignition, detonation sound), once I heard that I went 2 or 3 clicks toward rich, still after enough hours to replace the rear bearing, it's always has that dark brownish look.

I had a muffler come loose on me once too, it didn't fall off but it was hanging down and the engine did run pretty lean when that happened but I had time to land it before she blew. The header bolt holes were stripped, I probably torqued it down too tight to cause that, I prefer stainless threaded inserts or back nuts on the muffler header these days.
I guess I'm mainly wondering if you may have been running too lean for awhile?

Thanks!!

Joe

PM  EMAIL  GALLERY  Attn:RR  Quote
02-23-2018 09:16 PM  55 days agoPost 18
cudaboy_71

rrElite Veteran

sacramento, ca, u.s.

My Posts: All  Forum  Topic

As far as the “pitting”, it’s not. That’s remnants of the piston when I first opened it up. After a complete tear down and wash everything is nice and smooth.

As far as the lean run, I think I just brain-farted and leaned it out in cold weather rather than richen up. It doesn’t get cold here often enough to warrant more than a click or two max anyway. But that day was a cold snap and I think I leaned it 2-3 + 1-2 on mid. It might have been ok with that, but when the pipe came loose that cut the fuel pressure and put it over the top.

I’ve got two tanks through it now and it seems to be running much better.

As far as the buildup I’ve only had this motor for 2 1/2 gallons. It came on the used heli I bought and looked like that when I tore it down the first time.

if it ain't broke, break it.

PM  EMAIL  HOMEPAGE  GALLERY  Attn:RR  Quote
02-25-2018 02:04 AM  53 days agoPost 19
GeezerJoe

rrNewbie

Kernersville, NC USA

My Posts: All  Forum  Topic

cudaboy_71
As far as the “pitting”, it’s not. That’s remnants of the piston when I first opened it up. After a complete tear down and wash everything is nice and smooth.

As far as the lean run, I think I just brain-farted and leaned it out in cold weather rather than richen up. It doesn’t get cold here often enough to warrant more than a click or two max anyway. But that day was a cold snap and I think I leaned it 2-3 + 1-2 on mid. It might have been ok with that, but when the pipe came loose that cut the fuel pressure and put it over the top.

I’ve got two tanks through it now and it seems to be running much better.

As far as the buildup I’ve only had this motor for 2 1/2 gallons. It came on the used heli I bought and looked like that when I tore it down the first time.
Gotcha!

It's hard to tell in the photo that it's pieces of the piston on the surface.
Given the fact that it's a used engine, the previous owner may have run it too hot and weakened the piston already causing it not to survive the pipe issue.

Yeah, I've had quite a few of those brain farts in my time, I feel pretty dumb afterwards too!
Most of time I just hope nobody was watching.

My wife had a bird in a cage once (don't remember what species it was), the thing would fall asleep while hanging upside down, then fall on it's head, when it got up, it would look around quickly as if it was wondering if anyone just saw what happened. It was hilarious!!
That's what I do when I do something stupid!!

Thanks and glad you go it running good! :-)

Joe

PM  EMAIL  GALLERY  Attn:RR  Quote
02-27-2018 01:41 PM  51 days agoPost 20
GeezerJoe

rrNewbie

Kernersville, NC USA

My Posts: All  Forum  Topic

I was really curious about carbon in RC nitro engines so I done some research and I may be misunderstanding all of this but it appears that carbon mostly comes from castor oil rather than pure synthetic oil.

Apparently another contributing factor is a lean condition on the high end but that's not always the case.
I had an ABC airplane engine that had a fair amount of carbon on the piston and head, I called the guy I bought it from and he confirmed that he only uses castor oil.

I've always run 30% nitro with pure synthetic oil in my helis so that may be the reason mine is always dark brownish or bronze looking in color with no build-up.
Since these engines run so fast with really high compression ratios, just a few thousands worth of buildup can cause detonation and overheating even if it's not too lean. OS recommends using an additional .2mm (.008") shim to prevent detonation when using 30% nitro.

I've always associated carbon build-up with gas engines.

Again, I may be way off base with my research results!

All I really know is that if I lean mine out more than they are now, I can hear detonation and when I hit throttle hold mid air, the engine will hang on the pipe for a bit before dropping to idle.
For me, hitting throttle hold in flight is one of the best ways to tell if it's too lean, if it goes to idle right away, it's probably not too lean.
I don't go by smoke and temps alone. It took me a while to learn what it should sound like, until then, it was pretty frustrating.

Not trying to change topics, just trying to understand the cause of the carbon and the hole in your piston (beyond the pipe coming loose).

Thanks!!

Joe

Making notes to help remember things only works if you can remember where you put the dang note!

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 2 pages [ <<    <    ( 1 )     2     NEXT    >> ] 492 views POST REPLY
HelicopterEngines Plugs Mufflers Fuel › blew a hole in my 91HZ piston: cleaning procedure?
 Print TOPIC  Make Suggestion 

 7  Topic Subscribe

Thursday, April 19 - 10:34 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online