ASP .91 FS (First 4stroke - looking for general advices) - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Jan 10, 2018, 08:23 PM
Right on the Edge!
Discussion

ASP .91 FS (First 4stroke - looking for general advices)


Hi there,

I've got my first 4stroke glow engine, an ASP .91. I'm getting it into a test stand and get to know it.

But I'm new to 4strokes, and thus there are a few things I'm wondering about. Thanks in advance.

1) Let's start with the prop. The manual says 13x8, unspecified if it means for break in or for flight. I've been told this engine can handle up to 15x5 or so. I don't necessarily want to go up to 15" but I was hoping for a 14x6 or maybe 14x7. So what do you say? Both break in and flight.

2) I know I'll have to check valve clearances, but I'm not sure exactly how to do it and what to do. Do I have to remove also the lateral plate or just the upper lid that covers the valve arms? (English's not my first language, I beg your pardon)

3) Which temperatures should I be expecting, at the ground at first?

4) I have a 280 ml fuel tank that I was using for a 10cc gasser. Are 280 ml of methanol enough for 7-8 minutes flight (aerobatic)? I don't need anything longer.

5) This is important: fuel tank installment and engine orientation: is there anything I should pay attention to? I'd like the engine to run at all throttle position (especially idle) in ANY orientation, without it dying... I've had a quite bad experience with small gassers (some of you might well remember): engine dying when the nose is lowered, and stuff like that. I know in theory 4strokes are less prone to fuel pooling at idle, and that, in general, glow engines suffer less from this kind of issues as compared to gas counterparts, but as one has said in this forum, "failure brings paranoia", so... here paranoid I am.

I think that's all for now... thank you
Sign up now
to remove ads between posts
Jan 10, 2018, 08:46 PM
Registered User
Valve clearance is easy, once you've done it a couple of times.
You only need to take off the valve cover, and turn the piston in top, where the valves are closed. Very easy: just turn to top, and observe the valves. If they are moving while turning to top, turn the engine ONE revolution more, and you will see that both valves do NOT move when the piston is in top.
Then place a 0,05 or 0,1 mm (both values are acceptable) feelerblade between valve stem and tumbler (rocker), with the adjusting screw on the other side, adjust the clearance while moving the feelerblade back and forth untill you feel a slight drag on the feelerblade.

Then carefully tighten the locknut, making sure you hold the adjusterscrew so it does not move. Important: the locknut just goes snug, it does NOT want to be tightened down forceful.
After locking the nut, recheck the clearance to see if nothing has moved during tightening.

Can't say much about temperatures, very depending on your method of measuring.

280 ml should be OK for about 8 minutes of full bore running, is my estimation.

Installation of tank, like any other engine: centre of the tank roughly level with the spraybar, but this is not too critical, especially not when using muffler pressure...
Jan 10, 2018, 11:11 PM
Registered User
Follow the advice of Brutus1967 and you will be just fine. As far as what prop to break it in and run it on, a 14/6 will work great for both. If you want a lighter prop load to do the break in on then go to a 13/6 and it will rev a little higher while keeping the temp a little lower. A 14/6 is my favorite for all around sport flying with this engine and a 13/8 is better for more top speed at the expense of a little thrust. I have tried a 15 inch prop on mine before and I didn't really like it too much. RPMs were around 7800 and pitch speed wasn't enough to satisfy me. With a 14/6 I'm getting 9600-9800 RPMs and thrust is Awsome and the pitch speed is plenty fast for sport flying.

Mike
Jan 10, 2018, 11:23 PM
Registered User
Quote:
Originally Posted by gmwahl
With a 14/6 I'm getting 9600-9800 RPMs and thrust is Awsome and the pitch speed is plenty fast for sport flying.

Mike
What altitude are you? Because I get basically those numbers on gasoline with an APC 14 x 6, maybe a touch lower, like 9500 or so....
Jan 11, 2018, 01:33 AM
Right on the Edge!
As for the prop, I'm then going to try a 13x6 first, then 14x6 or maybe 13x7.

Do these glow fourstrokes really mind the orientation in which they are installed to the firewall? Or I should say: is operation of the engine influenced in any way accordingly with its orientation?

Because, looking at where the needles are, it seems to me that the only position in which you can easily access both of them (plus inserting the glow igniter) is either with the head up or down, 90 in respect to the ground.

The plane is supposed to be flown inverted and knife edged, so if an engine doesn't like orientations different than head-up, this could be a problem.
Jan 11, 2018, 02:08 AM
engine-a-holic
Use a chicken stick or electric starter. This engine starts well by hand, but can give quite a big wack on the fingers. It's usually a first backflip starter, from experience.
Jan 11, 2018, 07:25 AM
ARFs Are Me
TomCrump's Avatar
Quote:
Originally Posted by Hlaalu11
As for the prop, I'm then going to try a 13x6 first, then 14x6 or maybe 13x7.


.
I've been running a 14X6 on my inverted .91. I broke the engine in, on the air frame, with the same prop.
Jan 11, 2018, 08:32 AM
Registered User
Quote:
Originally Posted by Hlaalu11
As for the prop, I'm then going to try a 13x6 first, then 14x6 or maybe 13x7.

Do these glow fourstrokes really mind the orientation in which they are installed to the firewall? Or I should say: is operation of the engine influenced in any way accordingly with its orientation?

Because, looking at where the needles are, it seems to me that the only position in which you can easily access both of them (plus inserting the glow igniter) is either with the head up or down, 90 in respect to the ground.

The plane is supposed to be flown inverted and knife edged, so if an engine doesn't like orientations different than head-up, this could be a problem.
I have seen them in every orientation from upright, slanted up, sideways, slanted down and vertical down. They really do not care, with only one note: when vertically down, they can suffer from oil pooling in the head during storage, which can make the first start of the day tricky, so it can be convenient to have at least the plug easily accessible for removal and draining the oil.
If the engine is cowled, using the choke valve supplied can be very convenient, but most people just close off the muffler with a fingertip in order to get fuel into the carb....
Jan 11, 2018, 08:41 AM
Registered User
Cougar429's Avatar
Welcome to the world of 4-strokes. You will be pleased with their power, lower noise and fuel consumption.

The valve adjustment you asked about has been covered, except to say I personally check it at the beginning of each season and may only have to again part way through. Once an engine has been broken in and wear settles down not too much to worry about.

Along with the standard recommendation to add a fuel filter to the carb feed line, (these seem to be less tolerant of contamination) and have a spare glow plug on hand, will add some safety advice.

Use a chicken stick or electric starter. You can get quite a kick when they fire.

WARNING: Ensure you have the prop danger arc clear of any persons, yourself included, if the engine is above idle. That arc consists of the half circle from the prop plane forward.

The risk is that 4-strokes can come to an IMMEDIATE stop if lean at higher throttle. No lock nut system may be able to retain the prop, which comes off with considerable energy. Believe me, I have seen and had this happen when first working with these and can confirm the risk.

Once the engine is set up it should be fine, but not worth taking the chance of encountering it again so keep that area clear.

As for fuel tank size I would recommend trying to fit a 12 oz, (approx 350ml) to ensure your 7-8 minute flight. I set the timer on my Tx for 9 minutes and in most cases can expect 1/2 tank remaining. Mind you, it all depends on throttle; At full you can estimate a 91-100 will burn 1 oz/min.

To address you concern for dead sticks, as with any other installation you want the mid level in the fuel tank to be even with the fuel inlet nipple on the carb. I side mount most of my 4-strokes and have never encountered any problems, Full inverted is another story and one installation requires onboard glow. Again, the condition of the engine makes a huge difference and even if not fully broken in they can be finicky in any position.

One other thing to consider. What airframe will you be mounting this in? 4-strokes do not have the internal airflow through the case so adequate cooling airflow is even more critical. Both inlet and outlet area need to be addressed.
Jan 11, 2018, 01:10 PM
Registered User
Brutus,

I live and fly at 5900 feet elevation. I used a Master Airscrew 14/6 to get those RPMs. With my engine (Magnum .91, but same engine as ASP) I get my most consistent running between 9600-9800 RPMs, but have got it to hit 10k. It won't sustain 10k without the idle and midrange going a bit screwy, so I set it for less RPMs and it is dead solid and reliable. I have not tached it with a different brand of prop on the 14/6.

Mike
Jan 11, 2018, 01:51 PM
Registered User
Psssssst , just between us I've got one too . Not only could it have flown in a plane from the 1st flick it never skipped a beat . Its even made in China and everyone knows what that means . Although in the spirit of transparency there alloy cases could be a bit harder . Another secrete I got it from from H.K. for $129 aus. and I've even have to admit I get even good to great warranty and customer service from them as well ! Could this even be true ? Or am I dreaming or telling lies . You be the judge .
Jan 11, 2018, 01:54 PM
A man with a plan
Balsaworkbench's Avatar
If you are using your old fuel tank, make sure your tubing is compatible with methanol.
Jan 11, 2018, 05:31 PM
Right on the Edge!
Thank you so much for all your inputs.

Quote:
Originally Posted by TomCrump
I've been running a 14X6 on my inverted .91. I broke the engine in, on the air frame, with the same prop.
This sounds encouraging, but opinions seem to vary a little amongst yous (as seen above).

Quote:
Originally Posted by Cougar429
The valve adjustment you asked about has been covered, except to say I personally check it at the beginning of each season and may only have to again part way through. Once an engine has been broken in and wear settles down not too much to worry about.
I've seen a couple of YouTube videos, and in fact I've to say: it's probably gonna be easier done than read. But I've to get a feeler blades set first. I'm new to fourstrokes and this valve clearance checking thing seems to me to be "the thing" with fourstrokes, in terms of maintenance. Well, good it's not too complicated.

Quote:
Originally Posted by Cougar429
The risk is that 4-strokes can come to an IMMEDIATE stop if lean at higher throttle. No lock nut system may be able to retain the prop, which comes off with considerable energy. Believe me, I have seen and had this happen when first working with these and can confirm the risk.
I'm definitely gonna use a chicken stick and maybe even an electric starter. At the beginning I was skeptical (I've always hand started the two gassers I've owned), but more than one of you has recommended cautions, so let be it. I'd prefer the chicken stick because (maybe it's just my own wacky philosophy) I like to learn how to hand-start each engine. It seems to me it's like a part of "knowing" that engine better.

Quote:
Originally Posted by Cougar429
As for fuel tank size I would recommend trying to fit a 12 oz, (approx 350ml) to ensure your 7-8 minute flight. I set the timer on my Tx for 9 minutes and in most cases can expect 1/2 tank remaining. Mind you, it all depends on throttle; At full you can estimate a 91-100 will burn 1 oz/min.
I see. I am used to very short flight times (in the order of 6-7 minutes), but as you say, it's better to finish a flight with the tank still half full. I was asking that because this frame is very narrow and a 350 ml tank I'm not sure would fit. But, one thing I didn't mentioned is that I'm not going to fly full throttle all the time. Also, to answer the frame question: this engine is going to go into a 57" Edge (around 91 oz, 2,6 kg), which previously was 10 cc gas-powered and currently it is electric powered (6S). Right now I'm doing standard aerobatics sequences and I'd like to use it the same way with this engine, plus some (of what people loosely call) "3D maneuvers".

Quote:
Originally Posted by Cougar429
To address you concern for dead sticks, as with any other installation you want the mid level in the fuel tank to be even with the fuel inlet nipple on the carb. I side mount most of my 4-strokes and have never encountered any problems, Full inverted is another story and one installation requires onboard glow. Again, the condition of the engine makes a huge difference and even if not fully broken in they can be finicky in any position.
Please forgive me asking, but English's not my native language and I'm not 100% sure of what you mean by "one installation" there. So you're suggesting to install a CDI if the engine is going to run inverted? Actually, however I'll mount it, IT IS going to run inverted because like I said I'm gonna fly the plane rolling it a lot. The only way to avoid prolonged 90 inversion would be to put the engine like 45 oblique, but then the position of the needles and the muffler come again to be an issue.

Also, and this is important: why the heck is the carb intake needle pointing up in the carb?? In this way you are force to make a loop with the lines. If the nozzle were pointing backwards, I could have linked it straight to the tank, with no curves at all...

Quote:
Originally Posted by Cougar429
One other thing to consider. What airframe will you be mounting this in? 4-strokes do not have the internal airflow through the case so adequate cooling airflow is even more critical. Both inlet and outlet area need to be addressed.
The cowl of this plane is already wildly drilled (for when it was with the 10cc), so airflow should not be an issue. You can think of it as almost no-cowl. I don't mind (and actually quite like, somehow) cowls that let see/access the inside.

Quote:
Originally Posted by Balsaworkbench
If you are using your old fuel tank, make sure your tubing is compatible with methanol.
I'm gonna replace the lines, but thank you for the input!

Finally, Bert (I couldn't quote your posts, don't know why), storage shouldn't be a problem: I'm going to store the plane nose up, hanged to the wall, so the engine would be parallel to the ground.
Jan 11, 2018, 07:55 PM
Registered User
Quote:
Originally Posted by gmwahl
Brutus,

I live and fly at 5900 feet elevation. I used a Master Airscrew 14/6 to get those RPMs. With my engine (Magnum .91, but same engine as ASP) I get my most consistent running between 9600-9800 RPMs, but have got it to hit 10k. It won't sustain 10k without the idle and midrange going a bit screwy, so I set it for less RPMs and it is dead solid and reliable. I have not tached it with a different brand of prop on the 14/6.

Mike
Ah, OK.... I live at sealevel, and that makes quite a difference. Currently on vacation in Indonesia, at 2200 ft altitude but a density altitude of about 4500 due to the tropical climate, I seem to lose more than 10% power. Fortunately I did overdimension the engine, so it's not a problem.

But your figures make more sense to me now.
Jan 11, 2018, 08:02 PM
Registered User
Quote:
Originally Posted by Hlaalu11
Also, and this is important: why the heck is the carb intake needle pointing up in the carb?? In this way you are force to make a loop with the lines. If the nozzle were pointing backwards, I could have linked it straight to the tank, with no curves at all...
It is a bit strange indeed, but so far it has not presented any problems, not even in my gasser conversions.

On both pics (.52 and .91) the fuel tube comes through the firewall at crankshaft centreline, loops around the intake manifold and plugs into the carb.
If it is not a problem with gasoline, then it sure will not be a problem with glow fuel, as glow fuel is lots less sensitive in this respect.


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Newbie first build. Looking for advice. icebuken Micro Multirotor Drones 0 May 29, 2017 09:07 PM
Discussion Looking for advice on first RC jtomlin Car Talk 38 Feb 06, 2017 10:03 AM
Help! Looking for advice on a first FPV racer hackdroot FPV Racing 12 Dec 15, 2016 01:33 AM
Discussion FIRST BUILD: Looking for advice on Sweepwings Juggernaut. uninc4life2010 Flying Wings 4 Apr 07, 2016 12:43 PM
Discussion ASP .91 4stroke failure Southern335 Engines 11 Jun 20, 2013 09:49 PM