ASP 52 2-Stroke Slow Pick-Up

[Colin S]

Has anyone solved the problem of slow pick-up when opening the throttle after a period of idling or slow flight? I'm reading that the engine is notorious for this characteristic and is labelled a "2-speed" engine. The engine requires a very accurate and lean idle needle set-up, but my pick-up after a few secs at idle is fine. Plugs used - OS 8, OS A3, Enya 3, Model Technics Supercatalytic, currently OS-F 4-Stroke. Fuel Southern Modelcraft Double-Lube High, 5% nitro. Prop Bolly 11-1/2 x 6, to slow down the model, previously RAM 11 x 7.

[Former Member]

[This posting has been removed]

[Colin S]

No, that's fine Tom. The pick-up is immediate so long as the idle time to opening the throttle is no longer than (guessing) about 20 secs, not long enough for me to get the model to the take-off point. The idle needle setting on these engines is only about 1/2 turn open at fully closed throttle. It's taken me a long time to find that out.

[Denis Watkins]

Colin, my favourite motor size, and no slow pick up On

A motor that is " run in "

Model Technics 10% fuel of your choice

An 11 x 6 prop of your choice, balanced

Your plug OS F only, no other

Check the needle O ring and substitute if needed, and do the bit of fuel pipe trick to seal

Your critical needle is a clue to your problem

The main needle of these motors will still fly pouring smoke out and not deadstick.

They will fly 3 clicks under or over optimum, that's six clicks of movement without stopping

So critical needle on yours does suggest partial blockage or pressure leak

Or tappets with no gap

Edited By Denis Watkins on 26/07/2018 06:57:53

[Don Fry]

I had one of these, til I broke it last week. It ran like a watch, and had a very good carb. Setting it to run properly was the same as any other engine. OS no 8 plug, as that is the only plug I use on 2 strokes.

ASP 2 stroke engines are popular in my club. No issues with them.

You don't say how low you idle the moter. It could also be that it's going cold at full idle. Why not carry it out doing say 3000 revs.

One point, if the motor transits from idle to full cleanly, you should, when testing this leave the moter at idle for at least 10 or 15 seconds before seeing if it does the transition. This is to allow the fuel in the engine to settle at idle needle mixture.

But I would say, as long as you are not idling too low, the idle need is not set properly.

I assume it's had a couple of hours work and is run in. Mine took a good two hours to settle properly.

[Jon H]

I had two of these back in the day and they were great engines for the money. I fitted them to a twin and it went like rocket!

From the description of the issue i still maintain the slow run is too rich. Why? because unused fuel is accumulating in the crankcase over a long idle and that is then thrown into the cylinder once rpm increases. This causes the rich stuttering and slow pickup. If you lean it off a little on the slow end more you may find the engine picks up better. Dont be worried about the number of turns on the needle vs other engines. Just set your engine so its happy.

The os8 plug is the best choice for this engine in my experience. Mine went like stink on this plug.

I would also change fuels. The double lube fuel is really oily and its possible the oil accumulation in the crankcase at idle is the main issue. I would switch to a full synthetic fuel of no more than 18% oil and ideally 15%. Model Technics techpower 5 or laser 5 would be my recommendations.

[Denis Watkins]

Sorry about the F plug guys, I went into 4 stroke mode, am an idiot

[Jon H]

Posted by Denis Watkins on 26/07/2018 08:41:29:

Sorry about the F plug guys, I went into 4 stroke mode, am an idiot

Looking at the time of your post it was too early anyway so i think you are excused

[Denis Watkins]

Ha ha, thanks Jon, you are very understanding

[Bob Cotsford]

I had two of these, both ran on 11*7 APCs, Laser 5% from Model Technics, iirc plugs were OS #8. The one in my Wot 4 was sidewinder and after a few flights to run it in it never faltered. The other was 45 degrees inverted in a Panic and that was a lot more sensitive to the needle settings, though that may have been down to the mini-pipe on it's exhaust . It went like stink otherwise. It really needed to be set at a slightly higher tickover than the one in the Wot 4 for reliability. They both needed a good few tankfulls to really settle down.

[Colin S]

Thank you all for your help. It's much appreciated.
I've not tacho'd the idle, but it's set as low as my other 2-strokes and so that the model doesn't run away on its own prior to take off. I'll try it set a little higher.
I've packed the O-ring grooves of both needles on the atmosphere side with some greased fine cotton, so that the O-rings are restricted in their sideways squashing. That's working very well so far.
I wonder that the scroll/pin throttle barrel transition principle ever allows close control of idle mixture. The needle needs to be set within about 1/20 of a turn, according to other users and from my own experience. The pitch of the thread on the idle needle suggests that the setting must be held to within a small part of a thou. The slack in the scroll/pin fit is getting on for about 15-20 thou, so it's critically dependent on the spring pressure, and any side-force from the throttle linkage. I don't think many people reckon with this.
More to this: My engine is mounted side-winder in my Harmon Rocket. The axis of throttle barrel is in the vertical plane, which I believe is the dominant vibration plane for a single cylinder engine mounted this way. The barrel is quite heavy, so how far does the barrel move under vibration, given the slack?
My props are always balanced. I was also surprised to find that the Irvine spinner needed balancing, and it made a big difference to smoothness.
The engine has had several hours of running, including the running-in period, but still has a firm cold pinch.
I do the idle set-up after a period of full throttle, but I need to check that I'm giving it a long enough idle period for final setting of the needle.
Fuel: Yes, good thought, it is oily, and I chose that because my earlier ASP52 with an impossibly squeaky-tight pinch hammered out its big-end. I do have synth-based fuel to try. I did try Contest 10, but sensed that it was detonating a bit.
Plug: I read somewhere that the "aggressive" porting of the 52 can cause fuel splashing that can put out the fire, and here a shrouded 4-stroke plug can be a great help. That seems to to be evident in the general running, but it may be robbing me of a little power. I've never seen anything like the 12,800 RPM on an 11 x 7 RAM reported in the Just Engines review on any plug. I'm nearly 1000 down with both 52's I have. I've had to deal with fuel-frothing by using a sintered clunk, but in retrospect I'm thinking of restricted delivery and that it's a daft place to put a filter.
Thank you again. I plan to tackle the slow-pick-up first using the advice offered, and to revert to the OS 8 plug afterwards.

[Don Fry]

A point, if it has a "firm cold pinch", it's not run in yet. And fine tuning it can be a problem.

A work around that works, is put a delay on the throttle servo if your radio set supports delay, say a second closed to open. This tends to keep hesitant motors running. But don't tune with a delay servo, it just masks a problem, and you will not know if you have eliminated the problem.

I would not take too much notice of knockers of ASP engines. The are not as good as OS. But they run just fine, and when I broke mine, it was mourning a nice motor, not mourning what it cost me.

[Martin Harris - Moderator]

Posted by Denis Watkins on 26/07/2018 08:41:29:

Sorry about the F plug guys, I went into 4 stroke mode, am an idiot

I had hours of "fun" with a Super Tigre 90 some years ago which was fond of waiting until just before I was ready to take off to die on me - tried the whole range of known tweaks, orientation of spraybar etc. - even fitted a Perry Pump which liberated oodles of power (I had to fit an auxilliary fuel tank to cope with the increase in consumption!) but still it would idle for several minutes, then transition perfectly on test until I came to fly it and it would sense the fact and cut out...

The eventual cure was fitting an OSF plug, in desperation - it never missed a beat after this simple change!

[Colin S]

Don: My "firm cold pinch" on re-checking is not as firm as I thought, hidden by massive compression, but it's still a definite pinch. My relegated earlier 52 still has a very tight pinch, and I'd never again accept an engine so mismatched on its fits that it needed to levered-over.

I can't programme the Tx in that area, so it all has to be done digitally (fingers).

Not too many knockers, but my first info came from RC Model Reviews.

Martin: I'm using the OS-F, and it has brought benefits in the current state of setup.

You interest me by your Perry Pump comments. I'm wondering if fuel delivery is robbing me of the 1000 RPM I'm missing. I'm not losing a lot of sleep over it as the Harmon Rocket is what it is named, a Rocket. All rather intimidating at my age, since throttling-down to a less frenetic pace is not a consistent option.

[Colin S]

Ref my OS-F plug: OS list it as a cold plug, Nexus and other sellers as a hot plug, elsewhere as a "Mildly-hot" plug. Anyone know what it really is?

[Don Fry]

I will admit to having supped a very fine Malt, gloriously mispriced by my local supermarket.

But on a non technical level, I always thought that an OS F was fitted to all 4 strokes. Period.

[Colin S]

I'm not sure about Saito, Don. Certainly have been gaining popularity for some 2-strokes, especially when mounted inverted.

I prefer Lucozade.

[Colin S]

Sorry, Irvine, I malign your spinner. Mine is in fact a generic all plastic spinner supplied with the kit, nice to look at, but needing balance.

[Colin S]

Denis Watkins: Ref. your ASP 4-stroke comments.

I use an ASP 52 4-stroke in my Veron Hawker Tomtit, and for 50 flights or more it's been going like clockwork., no issues. Ref. your list -

I use a Master Airscrew K-Series 12 x 6 for this model, which is an excellent match model to engine.

10% Southern Modelcraft Synth-Based fuel

OS-F

O-ring grooves for the main and idle needles wrapped with a few turns of fine cotton to restrict the sideways squashing of the O-rings, seems to stabilise and stiffen the needles nicely.

Engine very uncritical on settings. Can be seen/heard here -

[Colin S]

https://www.youtube.com/watch?v=d3Yu05wAkqs

[Denis Watkins]

Perfect Colin, these are my favourite motor size. I had a Condor Moment with 2 and 4 stroke, and suggested to drop a prop size to get the tickover.

Although not vital, I do favour 10% in 4 strokes, as in the smaller sizes it does help power, with the SC30, the 10% transforms the motor. I have a full set in different makes, the 26, 30, 40, 48, and 3 52s all flying.

[ASH.]

Excellent video Colin and a beautiful model..

On my Irvine 53 mounted inverted I had to use an OS F plug to ensure a consistent idle and eliminate flame out. It did advance the ignition and I got some detonation (pre ignition) which I feared would blow up my engine or damage it at least. But it was cured by acutely leaning out of the low end needle. I used a heavier 12x6 Graupner prop and Contest 10 fuel. I did try 5% but noticed a considerable difference in power.

Edited By ASH. on 27/07/2018 17:58:15

[Colin S]

Denis: I've used the 10% on what seems to be universal recommendation, and the engine seems very happy with it . The ASP 52 4-stroke provides a good power margin for aerobatics, and it allows me to do quiet low-fly-bys at low revs. However, with the current set-up using a 12" prop and an idle faster than I'd like, I am troubled with runaway on tarmac.

I'm interested in your rationale on a smaller prop for better idle, when I would have expected some advantage from flywheel effect. I'm using 12" to try to preserve something like scale, as the prop on the full-size as very large, but I think I'll have to look at your suggestion and see how the idle goes.

Ash: Thank you for your comments, David Hayward in our club does some excellent work - about 13 videos here - https://www.youtube.com/watch?v=fsF5aXvnxN0&list=PLaGIpNUnjiJq3w9sTxgdQ21H8eu3eTv-I

I'm still trying to determine what heat range the OF-F actually is, as per my earlier post.

Going back to the ASP52 2-stroke, I'm going to try some 10% nitro Synth-Based to reduce the castor content in my usual fuel as suggested. One day I hope to find-out where my missing 1000 revs are.

[ASH.]

I'm confused.. Are we talking about an ASP 4 stroke or 2 stroke? I keep reading about both on this tread.

"One day I hope to find-out where my missing 1000 revs are".. Lol. I know exactly where your 1000 revs have gone Colin. They've been sucked up by the oil and not enough nitro.

It's because of the excessive oil content in your SM Hi lube and because you're using only 5% nitro.

On my Irvine 53 there was a marked difference between 5 and 10% nitro.

On my Saito 72 4st I was getting 8500 rpm @ WOT on APC 14x6 prop with Contest 10, which contains 18% total oil (3% Castor, I'm ol' school). As an experiment I decided to reduce the oil content. If Jon can run his Lasers on 10% then why can't I?. I did a lot of research on the net and found many experienced modellers had done the same with positive results. I was always a bit skeptical in believing that oil could cause any kind of significant drag.

So, I diluted the Contest 10 with 50% pure Methanol to get 12% total oil and 6.6% nitro. To my amazement the revs went up and I had to screw in both needles. The main by over half turn and the idle by a quarter. It can go more but I'm happy with the results. At WOT I get well over 9000, on idle 2800. The engine runs a bit hotter but it's acceptable. The big difference is in fuel economy. I fly for 12 minutes and land with third tank full. It's an 11oz tank. Before, 12 minutes would empty the tank. And there's hardly any oil on the model to wipe off after. That's also down to exhaust and vent position.

My suggestion Colin is use a fuel with less oil and 10% nitro,. Do let us know you get on.

PS. Do not run the engine @ WOT for more than a few seconds at a time when tuning. You'll cook it. Don't ask me how I know

[Colin S]

Hi Ash: Thanks for your interest and comments.

First, 4-strokes: This was mission-creep, arising from earlier comments mistakenly offered on the ASP 52 4-stroke, which I subsequently answered.

Nitro content: I've always used 5%, based on engine tests by RC Model Reviews and Just Engines. Just Engines oil content was 10% synth/5% castor, Flair Gold. My use of 9% synth/9% castor reflects my concerns over the completeness of running-in, and in the way what seemed to me ridiculously tight pinch which soon saw-off the big end of my first 52. I presumed slack there was robbing me of compression ratio and thus my famous 1000 RPM, hence my buying of a second engine.

However, I do have 10% nitro, 15% synth/2% castor to try next. I can't run engines at home due to noise, and my flying site is only available weekends. For less oil content I'm going to have to look around for a different fuel, or add methanol and nitro to my current stock. I have the nitro, no methanol.

Oil Drag: That's an unknown to me, but in addition to that, excessive oil is reducing the concentration of methanol and nitro. That must count also?

One thing this long period of impossibly hot weather has done is to provide me ample opportunity to think these things out, including the criticality of the throttle barrel contact with the scroll pin when the idle needle needs to be set within 1/20 of a turn of a very fine thread. Interesting also to try to work out what happens in the crankcase with a long idle, the flash-point of methanol being so much lower than the gathering oil

You refer to cooking the engine at WOT. You say - don't ask, but I need-to. In which way did your engine suffer?