Align 91H strange temp. increase ! HELP!

[DenisFerrari]

Hi all,
Flying with my trex700n + Align 91H + Coolpower 30 with no problema at all. i do not do 3D, just normal flight.
Noè, afte more or less 120 flights with tris set, in the very last flights I've notice a strange slight - but appreciable - temperature increase of the engine. After the flight I can measure around 105/110 Celsius degrees on black head (parts around the glow plug) and 60/65 on the back. I,'ve always been used to read around 85/90 pn the head and 45/50 on the back.
Using same thermometer, same ambient temp. Conditions and so on.
Even getting mixture reacher and reacher does not take temperature too much down.
Engine does not sound anything strange at idle and during normal operation, and it still works beautifully during the whole flight.
Just inspected the cylinder top and and side (unmounting the muffler) and it really looks very new, no marks or signs that could make think at something bad inside.
Moving engine by hand does not produce any suspicious sound on the bearing side ... Maybe the bearing anyway to be changed ?
Tried to change the glow log (always used OS8) and nothing changes to engine temperature.

Finally, since last March, I've started to flying with a new Raptor 903d, same engine of course so far much newer) and - like it's always happened to the rex700 engine until few weeks ago - I always read 80/85 on the head and 40/45 and the back ...

So, what do you think could be the reason for this strange temp. Increase ? Also, do you think it's better to change bearing ... Or something else .. Or engine directly, to avoid any risk ??

Looking forward for any appreciated suggestion you have,
Thank you so much and all the best,
Denis Ferrari

[aww]

Might be way off here but just check your muffler is sealed. I got a lean run from mine causing a piston ring to fail, just because of a slight leak
Anthony

[DenisFerrari]

Originally Posted by aww

Might be way off here but just check your muffler is sealed. I got a lean run from mine causing a piston ring to fail, just because of a slight leak
Anthony

Checked already, Muffler's perfectly sealed.

[aviator493]

Could be leaning out do to air leak/fuel distribution problem. I'd check all lines/hoses and maybe even clean out carburator.

[Al Miessner]

What kind of clunk are you running? If the foam fuel magnet it might be breaking down and clogging your filter/Carb. Other wise check your needles they might have rotated from vibrations.

[ShankBones]

Same 700n/91H, I was having similar various temp issues due to a loose carb at the base and causing it to get hotter and change mixture.

All I did was tighten the carb base bolt at the crankcase and all temp and mixture issues were gone.

[DenisFerrari]

Tubes are fine, carburetor locked and clean, everything looks normal. Inspected the back bearing looking don back cap and it does not seen so bad.
Maybe time to change it.
Do you think after my 120 flights (70/80 liters of Coolpower 30) could be time to hanged all 3 bearings ...?
Denis

[DenisFerrari]

...just another note : just had other 3 flights and at the end ov every one I have in fact noticed an abnormal temperature of 105-110C at head top (close to glow plug), around 90/95 at the point where the black head starts and 55/65 on the back cap point. also touching with finger makes feeling the difference... It is surely hotter than normal, even if it already runs just perfectly.
It seems to me to hear a slight soft sound ... Similar tho when one blade stickers is not completely adherent to the blade end ... Maybe it comes from the base bearing. No other strange sounds felt.
Finally, I've tried to make mid and max 2/3 click richer and in fact the temp does not go down more than 3/5 degrees..
Yesterday evening I've also unmounted the back cap and inspected the bearing ... Looking frommthere it seems in very good condition.
Between today and tomorrow I'll try to unmount the engine and open it to do a better check.
My actual sensation is that after 120 flights (70/80 liters of fuel) it's anyway maybe time for bearing changing and it should solve, so I'm surely gonna do this asap.

Any best method to take bearings out ?

Any opinion and suggestion is extremely appreciated,
All the best,
Denis Ferrari

[Al Miessner]

easy tricks
1) take apart the motor removing the card and anything else that can be taken off
then preheat the oven/range to 375 deg F or 190 C and put in the oven for 10 min
on a cooking sheet. when done carfully remove the motor from the oven and tap against a wood surface and the bearings will fall right out,
Al

[beans07]

Change of running can be a sign of needing new bearings. While your at it for peace of mind change out all your fuel lines as well. Whilst changing the bearings out check the ring for signs of wear since your engine has been getting higher temps.

[DenisFerrari]

Hi all,
just finished unmounting engine from the hely and completely unmounted.
See attached photos.
Cylinder is in a good condition, before cleaning it was in a very light brown colour and very lubrificated. Only thing noticed is light mark on one side, close to the ring.

The 2 bearings seems fine, even if the main one is slighly grainy ... I really hope it's the cause for higher temps.
For sure I'll change all fuel lines before remount.

What do you think and looking at the attached photos, would you change only the bearings or it's maybe the case of change cylinder and the rest (ring...) ?

Thank you for any appreciated suggestion,
Best regards,
Denis Ferrari

[lucien]

Originally Posted by DenisFerrari

Hi all,
just finished unmounting engine from the hely and completely unmounted.
See attached photos.
Cylinder is in a good condition, before cleaning it was in a very light brown colour and very lubrificated. Only thing noticed is light mark on one side, close to the ring.

The 2 bearings seems fine, even if the main one is slighly grainy ... I really hope it's the cause for higher temps.
For sure I'll change all fuel lines before remount.

What do you think and looking at the attached photos, would you change only the bearings or it's maybe the case of change cylinder and the rest (ring...) ?

Thank you for any appreciated suggestion,
Best regards,
Denis Ferrari

That mark on the piston does look a little suspicious, probably the result of a small seizure at some point in the engine's life. What side of the piston is it and is the liner clean? Usually after a seizure, there's a little aluminum laid down on the liner where it scraped off the piston.

Otherwise, the engine looks great to me after 70 gallons of fuel.

If a bearing is rough, I'd go ahead and replace it. But I'd also go ahead and replace the piston (and ring) too if you can afford it. That does look like a small seizure mark and those kinds of things don't heal themselves and in fact just get worse over time. Also look for any scoring on the inside of the liner.

That'd be my take on it,

LS

[beans07]

You can't tell if the rear bearing is bad until you take it out. By the look of the rust on the crank I would say that it is possible that your rear bearing balls are starting to pit and breakdown. Also it's not just rough running of the bearing it's the play in the inner cage. You will know this when you take it out.

Also replace the ring it looks like it needs to replaced as it looks pretty shiny. The piston will be okay but I would definitely replace the rear bearing and ring.

If your going to replace the piston also replace the gudgeon pin and the little e clips, don't reuse them. If you have had 70 gallons look for wear of the piston on the crank and gudgeon pin because that is a lot of work on an engine.

[DenisFerrari]

Thank you for all your suggestions!
One note : my engine has 70 liters (NOT gallons) of life

[DenisFerrari]

Originally Posted by lucien

That mark on the piston does look a little suspicious, probably the result of a small seizure at some point in the engine's life. What side of the piston is it and is the liner clean? Usually after a seizure, there's a little aluminum laid down on the liner where it scraped off the piston.

Otherwise, the engine looks great to me after 70 gallons of fuel.

If a bearing is rough, I'd go ahead and replace it. But I'd also go ahead and replace the piston (and ring) too if you can afford it. That does look like a small seizure mark and those kinds of things don't heal themselves and in fact just get worse over time. Also look for any scoring on the inside of the liner.

That'd be my take on it,

LS

Hi,
the inside of the liner is just perfect, no signs.

The part of the piston where a little seizure has happened (if seizure has been) is in exact correspondence to the exhaust hole on the liner and it perfectly corresponds to the small part where the liner exhaust hole is "vertically divided" by thin material ... I hope to be clear enough. ...

So, considering this, do you think it has been a seizure or just piston consuption/adaptation passing over the line ehaust hole vertical thin metal strip ?

Finally, the ring has not material and it "only" more shining in exact correspondence to piston mark...

Denis

[lucien]

Originally Posted by DenisFerrari

Hi,
the inside of the liner is just perfect, no signs.

The part of the piston where a little seizure has happened (if seizure has been) is in exact correspondence to the exhaust hole on the liner and it perfectly corresponds to the small part where the liner exhaust hole is "vertically divided" by thin material ... I hope to be clear enough. ...

So, considering this, do you think it has been a seizure or just piston consuption/adaptation passing over the line ehaust hole vertical thin metal strip ?

Finally, the ring has not material and it "only" more shining in exact correspondence to piston mark...

Denis

Yeah could be - it's hard to tell from the pics. But it does look strange to me even though seizure marks tend to be over a fairly wide part of the piston face (and usually lay down aluminum in the liner). If it's just a stain, it may very well be OK. I've not seen this pattern before on any of my motors, tho. Usually it's an even deposit right below the ring around the face of the piston (blow by).

So I personally would be conservative and replace the piston along with the ring anyway, if it's an affordable part. You don't want to have to get back into the engine again for the longest time possible, so a little precaution can go a long way here.

But that's just me, ultimately it's your call...

PS: I also agree with replacing the pin and circlips (if any) along with, especially if there's any ovalling. Also check for ovalling in the small end of the rod. There will be some after that much running, but if you can really rattle the rod around in there, I'd replace the rod also.


LS

[bloftin]

What kind of clunk are you running?

[DenisFerrari]

Originally Posted by bloftin

What kind of clunk are you running?

Using 2.5mm internal diameter tubing and standard metal clunk inside the fuel tank.
Hely's perfectly balanced in flight, you can see the fuel leve just perfectly leveled inside the tank agile flying...

[bloftin]

Originally Posted by DenisFerrari

Using 2.5mm internal diameter tubing and standard metal clunk inside the fuel tank.
Hely's perfectly balanced in flight, you can see the fuel leve just perfectly leveled inside the tank agile flying...

The reason I'm asking is the stock clunk has one small opening that fuel can flow through, if small debris entered this opening it could clog it just enough to cause a lean run condition, and needle adjustments would have no effect as you described.

This happened to me once, when I would fuel the bird it would push the obstruction out of the clunk, then I would fly and pick it up again. I was chasing needles all the time. I would attempt to richen the mixture, but opening the needles had little to no effect.

I'm running a fuel magnet now witch cures the problem I just decribed and a few others as well.

You may want to throw a fuel magnet in while you have the engine out of the way.

Good luck,

Brian

[DenisFerrari]

Originally Posted by bloftin

The reason I'm asking is the stock clunk has one small opening that fuel can flow through, if small debris entered this opening it could clog it just enough to cause a lean run condition, and needle adjustments would have no effect as you described.

This happened to me once, when I would fuel the bird it would push the obstruction out of the clunk, then I would fly and pick it up again. I was chasing needles all the time. I would attempt to richen the mixture, but opening the needles had little to no effect.

I'm running a fuel magnet now witch cures the problem I just decribed and a few others as well.

You may want to throw a fuel magnet in while you have the engine out of the way.

Good luck,

Brian

Thank you for the suggestion.
I have no problems at all in keeping the engine mixture set, if I open the need els it just becomes richer and in fact making more smoke and increasing fuel consumption too.
The only problem is that in the last flights I've noticed a temperature increasing from 85C deg. To 110 on top of black head (close to glow plug), and from around 45C deg to 60/65C on motor back cap. I think the main reason is the bearings and I'm gonna change them asap.
Also, as yu can see in the photos, there's a slight shining Mark on cylinder top, just before the ring ... But it's in exact correspondence to liner exhaust hole, in particular to the very thin material dividing the liner exhaust hole in two ... So it's maybe not the cause of high temps...

Thank you
Denis