Need help with strange issue: needles swapped for OS 55 to run OK

[HeliBenj]

Ok I'd love engine gurus to chime in on this one.

I've been troubleshooting the origin of a nasty leaning problem I have where the HS on my 600N just goes crazy above 40% throttle. in normal mode (0 40 80) I get 2450 RPM at hover..... With gov on same issue.

This is after 5 tanks break in after engine rebuild.
I have checked all lines, filter, pressure nipple, tank, clunk, clunk line, carb tight, head bolts, back plate, needles settings, gov, magnet, gov bypassed, muffler tight

Strangest thing is I swapped the needles thinking maybe I had them wrong on rebuild, problem seems to be solved, engine idles good, spools up, holds gov HS, sweet. Only problem: the needles are not in their correct location (the mid is on the high and Vice versa)

Any Idea?

[Raptor30_V1]

Bonjour,

I'm definetly not an engine guru - hopefully they will stick in to help.

As you wrote, you rebuilt your engine. I can only think of 3 possible reasons:

1.) your carb barrel got loose (screw on the throttle-lever) - your throttle lever on the carb shows you the same position as usual - meanwhile the barrel itself turned to higher opening? Disengage the throttle link and turn the carb barrel by hand to check. Thanks to the marks on the carb this should be easy to check.

2.) Did you disassemble the carb completely? The mixture-control-screw on the OS-55 (I guess it's the same as on the OS-50?) turns a small barrel inside the carb. Did you dissasemble this part and put it together correctly?

3.) Some leakage - check engine screws, carb fixing, glow plug/thread - leads to a lean running as well

I have an Align-55, but as a pretty new engine I did not have to rebuild it, so it's difficult to say, what can be incorrectly done by rebuilding it. Correct me if wrong, but a HS of 2450 rpm means for a T-Rex600 Nitro an engine rpm of about 20'ooo (= throttle completely open) ?

J'espère bien que quelqu'un puisse t'aider mon ami,
Meilleurs Salutations,

Oliver

P.S: J'ai pas noté jusqu'à présent, mais quesque c'est la différence entre l'aguile mediane et l'aguile qui control le maximum? Je ne les ai pas étudié en détail, mais ils me semblent de la maeme taille?

[DustinB]

Just a couple thoughts.

First, what governor are you running? Did you happen to setup the governor to kick in in normal mode? Have you verified the headspeed setting on the governor? Have you watched the throttle arm to see what it is doing when the headspeed goes crazy?

Second, did you happen to move the throttle arm(if you removed during rebuild)?

[HeliBenj]

Originally Posted by Raptor30_V1

Bonjour,

I'm definetly not an engine guru - hopefully they will stick in to help.

As you wrote, you rebuilt your engine. I can only think of 3 possible reasons:

1.) your carb barrel got loose (screw on the throttle-lever) - your throttle lever on the carb shows you the same position as usual - meanwhile the barrel itself turned to higher opening? Disengage the throttle link and turn the carb barrel by hand to check. Thanks to the marks on the carb this should be easy to check.

2.) Did you disassemble the carb completely? The mixture-control-screw on the OS-55 (I guess it's the same as on the OS-50?) turns a small barrel inside the carb. Did you dissasemble this part and put it together correctly?

3.) Some leakage - check engine screws, carb fixing, glow plug/thread - leads to a lean running as well

I have an Align-55, but as a pretty new engine I did not have to rebuild it, so it's difficult to say, what can be incorrectly done by rebuilding it. Correct me if wrong, but a HS of 2450 rpm means for a T-Rex600 Nitro an engine rpm of about 20'ooo (= throttle completely open) ?

J'espère bien que quelqu'un puisse t'aider mon ami,
Meilleurs Salutations,

Oliver

P.S: J'ai pas noté jusqu'à présent, mais quesque c'est la différence entre l'aguile mediane et l'aguile qui control le maximum? Je ne les ai pas étudié en détail, mais ils me semblent de la maeme taille?

Hi! the high end needle has 2 o Rings and a thinner taper. It also has a groove cut where the splines are. The mid is thicker, one O ring, no groove.
1) checked
2) never touched
3) all checked...

Yes, the HS picks up like crazy, it goes from like 1700 RPM below mid stick to 2450 in one second or less, really scary

Nice French BTW!

Originally Posted by DustinB

Just a couple thoughts.

First, what governor are you running? Did you happen to setup the governor to kick in in normal mode? Have you verified the headspeed setting on the governor? Have you watched the throttle arm to see what it is doing when the headspeed goes crazy?

Second, did you happen to move the throttle arm(if you removed during rebuild)?

I'm running a Multigov Pro, pretty confident with the settings as it was running great before. No gov in normal mode.
The throttle arm just behaves normal, it opens in a linear fashion, and all of a sudden the HS gets sick, though I'm positive the servo and arm don't go full. Throttle arm / end points also checked.

This is driving me crazy guys

[DustinB]

Try again and watch the throttle arm when it transitions. I can't see any other reason for such a huge jump in rpm all of the sudden at the same point. I'm almost certain it has to be something with the gov.

[John Cook]

there was a guy who has a Multi gov pro on a YS56 and having a similar issue with over revving.

not sure why though. Call/email aerospire. They are usually great with service

[DustinB]

+1 on give them a call. Just for giggles though, completely disconnect the multigov and run on your normal curve first.

[HeliBenj]

I have already bypassed the gov completely (trottle servo directly in receiver), does the same.... It's not the gov.
Also swapping the needles fixed the problem, which leads me to a mixture issue

[Raptor30_V1]

Bonjour,

I agree, this seems to be a carburetor issue. Correct my if wrong, but anyway most other parts can't be rebuilt the wrong way? (Piston and rod excluded)

Just an idea I had yesterday, maybe the OS-50 Hyper carburetor might fit the OS-55 (most of us have an OS-50 Hyper?) - I know it's not perfect, but if so, you could check whether this strange behaviour really comes from the carburetor? If, by hazard, you have a 2nd OS-55, try its carb then?

Some further thing influencing a lot is the muffler. If muffler e.g. has broken parts inside or e.g. is full of dirt, fuel etc. the outcome can be pretty strange engine behaviour too, looking like someone sits on the throttle lever and playing around with it


I hope, this inconvenience will be solved pretty fast - on the other side I'm curious as well, because such things add a lot to all of our learning curves.

Meilleurs Salutations,
Oliver

P.S: Sometimes it helpes to have more detailed information on hand, as what engine/muffler combo, how where your needles (3) settings before the rebuilt, what was the reason for the rebuilt, what did you dissasemble and which parts where exchanged, needle settings after the needle-swap .. etc..