RunRyder RC
WATCH
 1 page 209 views POST REPLY
Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › OS 91 four stroke heli crankcase evac
03-02-2020 01:54 PM  26 days ago
Topic Vote1Post 1
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
OS 91 four stroke heli crankcase evac
I am running an OS 91 Surpass 4 stroke in a 600 size heli. the engine is mounted with the crankshaft upright. The crankcase vent nipple is in the camshaft housing, in front of the rear bearing.When the heli comes back to idle, I get some smoke out the muffler as the high vacuum pulls oil and fuel out of the crankcase. I remember seeing something about moving the crankcase vent nipple to a lower position when the engine is mounted like this, but my searches are coming up empty. Any of you four stroke guys from wayyy back remember the do's and don'ts of this?

SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-02-2020 06:49 PM  26 days ago
Notar

rrKey Veteran

Taxachussetts

MyPosts All Forum Topic
Not sure about that but i had a Vario 4 stroker that used this engine and it ran really nice until you did a loop and it died every time at the top of the loop. Only way to fix it was using one of those vibrating pumps on it. It ran fine after that.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-02-2020 06:56 PM  26 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
Yep, runs really great so far with tons of power, but just wondering, since it's an airplane engine mounted vertically, if the crankcase vent can be/needs to be moved. Love the way it sounds.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-02-2020 10:50 PM  26 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

I don't understand your point.

On your Pic, the vent is connected to carburator and problem was solved.

You are talking about a os91 4t than don't have this mod... Ok...

Two options...

1. Do the mod, connecting the vent to the carb. No more oil messing your heli.

2. Run a tubing from the vent and discard that near muffler or near strut/skids down there...

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-02-2020 11:00 PM  26 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
The nipple on the block is too high, so too much oil gets in the engine because it is mounted upright.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-02-2020 11:51 PM  26 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

As we said before... Run a tubing and put far away this oily mess.

Is you are concern of oil consumption, put a 30 cc little bottle with fitting to capture oil from the vent and run also a vent for this bottle.

Fly your helicopter and see what we got on the 30cc bottle.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 12:51 AM  26 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

The crankcase vent has a special procedure for lubricating crankshaft.
Check instruction manual.

IMO, if your motor is producing large amount of oil from this vent, the motor is worn out.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 12:55 AM  26 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
They used to relocate the crankcase nipple on these motors. I am asking if anyone remembers the specifics of the process.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:18 AM  26 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

Ok... You have two choices.

1. Eliminate vent between cam lever and front bearing. A tubing with a plug should be enough.

2. Install a cover plate with a vent fitting, so you are going to vent between piston and rear bearing. Run a tubing to vent far away motor.

This procedure don't eliminate the oil problem.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:36 AM  26 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
I did find some posts where people tapped their rear cover. Nothing specific to helis. The problem is not that it blows smoke, it is that with the engine upright, it gets a crankcase full of oil all at once.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 02:48 AM  26 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

Let me try to understand your proposal.

How Os 91 4t surpass original lubricate?

Main lubrication come from admision/escape valves operation. This oil travels from top chamber to cam lever and follover.

Correct oil ratio on glow is necessary to lubricate front bearing, rear bearing, cam lever and follover.

If you have large amount of oil coming from vent, you have a problem.

Posible causes?

A. Your motor is worn out.

B. Oil ratio of glow is higher than espected.

So, changing the vent position is not going to solve the problem.
Excess of oil is going to pass through front bearing if you close this vent or oil is going to come out from cover plate at bottom.

How OS solve the problem?

This vent was connected to carburator using a fitting on Inlet manifold.

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 04:19 AM  26 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
So, I guess your answer is, no. You can't recall the procedure for relocating the crankcase vent nipple in this engine.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:21 PM  25 days ago
w8qz

rrVeteran

Grand Rapids, MI - USA

MyPosts All Forum Topic
Not sure if moving the vent port is a good idea: it appears that the intended lubrication path for the cam shaft is blow-by / crankcase pressure through the rear main bearing, into the cam, and thence out the vent port. If the vent line leading out of the cam is closed off, seems like the cam would not get lubrication. Also, adding a second vent (i.e. in the backplate) would reduce or eliminate the crankcase pressure that is supposed to push lube into the cam.
Disclaimer: I've never tried running a 4-stroke in a heli, nor shaft up. I do have several fixed-wings with 4-strokes, and have two of those engines on-the-bench right now torn down for bearing replacement.
"The helicopter is much easier to design than the aeroplane, but is worthless when done. W. Wright"
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:34 PM  25 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
Yea, I don't know for sure if it was ever done on the OS. There are many threads on planker forums having success with moving the nipple. Like you say, the engines are not upright. I will keep searching and hopefully someone from the Xcell and Kalt days has run into this.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:42 PM  25 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

My drawing and porposal...

You see the two options...
Green and yellow

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:44 PM  25 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
Maybe use both? I wonder about vent 2 having a smaller hole? Some guys on the planker forum were using a nipple with a 1mm hole. That might help!
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 01:46 PM  25 days ago
BeltFedBrowning

rrKey Veteran

Kansas City

MyPosts All Forum Topic
That drawing really does look like my heli!
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-03-2020 07:26 PM  25 days ago
Rojoalfa

rrVeteran

Punta de Mata, Monagas-Venezuela

MyPosts All Forum Topic
/
/

Well... You may try option in green first... The idea is how much oil can you recollect on bottle...
You don't have to modify your setup.

How many flights do you need to do to fill that bottle?
Let see what happen.

Hahaha... My drawing... Your heli...

/
Saludos cordiales,
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
03-06-2020 06:27 PM  22 days ago
4 stroke flyer

rrApprentice

Dowagiac,MI

MyPosts All Forum Topic
NICE TO SEE SOMEONE STILL FLYING FOUR STROKE HELICOPTERS.
SHARE  PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 1 page 209 views POST REPLY
Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › OS 91 four stroke heli crankcase evac
 Print TOPIC  Make Suggestion 

 3  Topic Subscribe

Sunday, March 29 - 10:05 am - Copyright © 2000-2020 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online