Hello!
Just got my first four stroke engine. A ASP .91. I am going to use it in my U-can-do 46.
I have never set up a four-stroke before, only two-strokes. So I was wondering if someone could help me out a little bit here, since the manual didn't help me out much(Chinese quality!).

Do you have any guides or something? Or maybe you could explain a little bit for me?

Thank you very much,

Morten

If I'm not mistaken, the ASP .91 is identical to the Magnum .91 FSR. From the picture, I'd say they're virtually identical. Chances are there's nothing you need to do to the engine other than prime it, run it, and adjust it as you would any other engine. My experience with the Magnum 91 is that a 14x6 APC prop is just about perfect. You want to prop it to turn in the 9000-10000 RPM range.

If its a ringed engine, and I think it is, you want to run fuel with some castor in it to help seat and seal the ring. Don't run it blubbering rich. Also don't run it up to full throttle as soon as it starts, as you want to give it a chance to warm up (unlike ABC or ABN engines that you want to heat up quickly). After a few runs you might want to take off the valve cover and check the valve lash (get yourself a good feeler guage).

You'll want to use and electric starter until you get it broken in a tuned. After that, chances are you'll be able to start it with a quick backflip against compression.

You might find that this is too much engine for a U-Can-Do 46.

Brad

I'll add my 2 cents worth also (I have 3 Saitos and 2 OS 4 strokes).

The ASP is the same engine as a Magnum. They are made in the same factory, just different names put on them. Both engines are clones of the OS.

Break the engine in slowly. USE A TACH !!! In order to set up a 4 stroke you will need a tach. The first couple of runs keep the rpms to 6,000, then gradually increase the rpms over the next few tanks. While breaking the engine in, run the engine for about 5 - 6 minutes while varying the throttle then let it cool for about 15 minutes, then repeat.

Your MAX rpms are going to be ABOUT 10,500 (depending on the prop and nitro content).

Once the engine is broken in (typically about 5 - 6 tanks of fuel), adjust the engine to max rpms, then back off about 300 rpms. Once the high end is set, do the low end (I usually adjust my low end to about 1,800 - 1,900 rpms. The low end rpms will vary by engine).

After you adjust the low end you will most likely need to readjust the high end.

IF THE ENGINE IS NOT PRODUCING SOME SMOKE AT FULL THROTTLE IT IS TOO LEAN - RICHEN IT UP A LITTLE.

I highly recommend adding some castor oil to the fuel (about 3 oz per gallon). While the castor is a little messy, it will protect your engine from a "lean run". I have well over 5 gallons through my Saito 72 and the only thing I have had to do is adjust the valves after about 4 gallons.

I also highly recommend using an OS "F" type glow plug - I have had no problems at all using the OS "F" plugs.

I use 10% nitro fuel and have plenty of power.

Before flying, I use the "Nose Up" method to make sure the engine is running properly. Put the engine at full throttle, then pick the plane up and point it straight up and hold it that way for about 8 - 10 seconds. The engine rpms should stay they same. If the rpms speed up or slow down the high end is not adjusted properly. If you fly like that you have a high probability of a flame out.

As for the plane: RE-ENFORCE THE FIREWALL I have seen the firewalls come off just by a slight bump and I saw a U-CAN-DO firewall come off in mid air with a Saito 72. I also suggest re-enforcing the fuselage by the wing. It is a weak point an can break on a rough landing.

Personally, I feel the 91 is overpowering the plane. I have seen several U-CAN-Do's with almost unlimited vertical running OS 70's and Saito 72's.

Good luck with the plane and engine.

You can get a copy of the Magnum 91FS engine here; http://media.hobbypeople.net/manual/210970.pdf

It's pretty good and should answer your questions. It has break-in instructions, operating instructions even a troubleshooting guide.

I'll throw in my 2 cents as well...

Almost everyone I know has a 4-stroke and none of us use a tach.

Mount it in your plane, hook it up (Tank, throttle, etc)

If it did not come with a glow plug, make SURE you are using a 4-stroke plug

Close the needle and open it about 2 turns.

Prime the carb - 4-strokes like to start wet.

Then adjust it exactly as you would a 2-stroke.

Morten,

I have a few ASP's, and all of them have the exact manual that Oldvet posted. Is this not what you got?

Mike, it is seldom Idisagree with you, but I have to when you say not to use a tach. Once you are used to the engine, and know how it soundswhen running right, the tuning by ear is OK. A new prop size though requres the tack come out of hiding. For a new (or new to you) engine, espically your first four stroke, a tach is mandatory for the first setup. On an engine that needs a long break in like the Magnums do, you will need the tach to get the right richnes during the longbreak in. It a cheep investment, anddoesn't take much room inthe flight box.

Don

I have to agree with Campgems. The use of a Tach, especially for a new user, is cheap insurance that the engine can be properly adjusted. I am aware there are folks who think this is not necessary but the OP apparently knows nothing about 4 strokes and the Tach will save him possible heartache as he learns how to properly operate it.

Well, I dare say that I have broken in two OS 70s, four OS 91s, two Saito 82s, a Saito 100 and a Saito 125 all in the last two years (And just last night I found my tach which has been missing for three years )

The only reason I even OWN a tach is because a few years ago I was reviewing an engine and wanted to show a picture of the digital RPM readout.

Here's the deal...

You start the engine and bring it to full-bore. Assuming the mixture is rich, you start to lean it out. You will hear the RPM increase.

At a certain point, you will find about 5 or 6 clicks where there is little or no increase and then you will hear the RPM begin to fade - this will be followed very closely by the engine running very poorly and if you don't bring the needle back, it will quit.

Ok, so when you get to the point where it starts to fade (let's call it click 7), bring it back to click 1 or 2.

Now, nose the airplane up. The RPM should stay the same or SLIGHTY increase. If you hear a drop in RPM, you need to richen the mixture up another click or two. This is not rocket science.

Now, here is the problem with a beginner using a tach:
Ok, so this guy reads that he MUST use a tach, and that he is going to get 10,500 RPM (which sounds a little high to me). Now, in all fairness, Campy DID say, "depending on the prop and nitro content", but will the newbie remember that? Probably not. He'll remember that he MUST use a tach and to shoot for 10,500rpm.

I have personally had someone ask me to help him get his engine running right. The engine was toast because he was told he should get 10,000rpm and he was only getting 9800 on his tach, so he kept trying to lean the engine out to get that last 200rpm.

Tachs do not take altitude, humidity, prop size, prop length, fuel brand, nitro content, or the condition of the fuel into consideration. A tach tells you numbers. Numbers don't mean anything. You might get 9800rpm today, and have a warm front move in tomorrow and you only get 9700rpm. No matter what you do, your engine will not put out 9800rpm today.

I can see the tach junkies flipping out!

Now, someone please explain why you can tune a 2-stroke by ear, but you MUST use a tach for a 4-stroke when the procedure is identical?

Thank you very much guys! Alot of helpful information!
I'm not sure if Im going to buy a tach(they cost like 140$ over here!). But I'll consider it though.
And ppk: I did not get a manual like that. All I got was 2 sheets of paper, one with a "exploded view" of the engine, and one containing a tiny engine startup instruction, and a tiny bit of tuning info. Not very helpful, and no break-in info.

About the UCD being overpowered: I bought this engine from a tip from a guy who has been flying for many years, including this plane with the same engine. So I think it will be OK

Again, thank you very much!

Mike take a deep breath and then read highlighted statement at the top of every reply. I quote "<p align="justify" style="width: 80%"><font color="#000000" size="1">Please resist the urge to curse, flame, degrade, insult or embarrass someone in your post. We encourage the free flow of your ideas, but believe that they can be communicated (and received) much more effectively if you keep things civil. If you have to vent, take it offline. We carefully monitor posts and will ban individuals who engage in offensive conduct within the forums. Thanks. </font><font color="#000000" size="1"><font color="#00265e">(RCU Policies</font></font><font color="#000000" size="1">)</font></p>
There is no need to call us, who disagree with your position on using tachs, names.

Don

It was said with the best intentions I assure you

I tend to agree with just keeping it simple. Bolt it on, start it up, slowly lean it until it just starts to sag, richen it back to just below peak RPM, check the idle and transition, adjust the low speed mixture if necessary and fly. I've owned a couple of these, one under the Magnum name and one ASP. Both worked well for the price.

Lets not argue here guys

Well, im kinda falling for the "keep it simple" idea, since this is just a four-stroke engine. And not a spaceship, I think.

But if you got a good tip, keep'em coming!

I have found that I do not use the "choke" feature and have removed it from my engines. I suggest that you pay attention to the muffler/head pipe mounting. If it comes loose, it will wreck the threads. It is a good idea to check the locking nuts while the engine is still warm. I have two of these (magnum brand) and like them both a lot.

It should be noted that Magnum/ASP engines have a rather sensitive needle compared to say a Saito or other similiar engine.

So 1/4+ of a turn can be the difference between a properly running engine, and one that will not even start or idle.

Make your changes in slow increments.

Opjose, that is the truth. I cut my teeth on four strokes with a Magnum 52. I picked up an O.S. 52 and found it easier to tune. My first Mag 70 about drove me nuts getting it running the second day until I discovered that you started your idle mix differently that either the Mag or O.S, in that you screwed it out to a stop, then screwed in the recomended number of turns. Once I dialed it in, it has been a great running engine even with a couple of nasty ground contacts. I also have a couple Mag 91's.Same great running engines. Almost like your car,hit the starter , let it warm up a bit and away you go. Iseldom had to touch the mix untill the last of a jug if I hadn't been flying a lot. Irecently aquired a few large Saitos and was really susprised a the wide sweet spots on both needles compaired to either the Mag or O.S engines. They also seem to idle much better, to the point that shutoff isnotinstant like the O.S and Mag engins are. I'm guessing that as there isn't a throttle stop, that the rotate pin isn't allowing the barrel to fully close. They seem to want to set there and tick over at what seems like about 1K for a long time until it finaly quits. Don't carry my tach to the flight line, so I'm only guessing the RPM. I know it a lot slower than the 2K I tune to for idle.

Don

I found adjusting the low end on my Magnum 91s was easier with the plane running. You clearly have to be very careful, but adjusting it while the plane was idling for a smooth idle got me in the right range much quicker.

Brad

I usually adjust the low end with the engine running too. I have a very long, thin screwdriver to do it with.

But I don't advise this method without adult supervision

is there a secert about setting the low end? I seem to have problems getting it set right, go by ear with it too?

for low end, i also use a pinch test...takes a moment to respond due to lower fuel consumption. Be real careflu if you have a scredriver on the ls needle and are pinching with the other hand. It is a lousy time for a hiccup.

Use a tach to get the most from your 4 Stroke. Also, break in your engine per manual and it will last longer and run cooler. Adjust the low end with the fuel line pinch. At idle, pinch the fuel line to the carb. The engine should have a slight increase in RPM just before it cuts out. If the RPM's do not increase before it cuts off, it is too lean. You do not need a tach for the low end. A Horizon Hobby rep showed me how to use the tach to tune my Saito 125. After the engine has ran several tank fulls and is warmed up, run engine to full throttle. Use tach to get highest RPM by adjusting the high end. Once you reach the max RPM, richen the high end just a little to drop RPM's about 250-300. This ensures you are getting the max RPM's while not leaning out the engine when in flight. I have done this to my Saito 82, 100, and 125 and they all run great with wonderful flight times.

In my experience, the fuel line pinch method on the Magnums is not a good method until you're close. The easy way to set it is to set the high end a little rich of peak, then bring your throttle down to the lowest speed it will continue to idle at (this may be fairly high to begin with). Now use a long thin screwdriver to slowly adjust the low speed needle until the engine begins to run smooth. Go back and reset your high needle (yes it will change). Bring it down again to the lowest reliable idle (it will be lower). Repeat this cycle until you have a nice reliable low idle (should end up arount 1750 rpm or so, depending on prop), and smooth transition from low to high with no hesitation. Additionally, you'll find that when you come down to idle from high speed, the engine RPM should be pretty stable (not speeding up or slowing down as it sits). You can then check it with the pinch test, but I'm willing to bet you'll be right where you want to be.

Brad

thanks Brad, I'm having problem with 2 magnums, a 52 and a 70, is it also true that mgnums don't transition as good as other 4 strokes?

There are several ways and none of them are a secret. Something I started doing last year, this is very helpfull for Saitos because the factory sets them so fat, works on all glow engines though. I have the engine all warmed up and with the engine running and the glow driver on I remove the glow driver, if the engine drops in rpm I put the glow driver back on and lean the low end then remove the driver again, it the rpms drop I do it again. When the rpms no longer drop I open it up just a little bit, low end is adjusted.
TACHs, I have always adjusted by ear, no problem. I had three tachs and all were total crap. Then I got a TNC Tach for prop testing, does a wonderful job for that on gas or glow. Then I started using it on my glow engines just because. It really does work a lot better then my mark one ear ball on most engines. No, I don't use it all the time but if I really want to see what an engine is doing then out it comes. Not all Tachs are created equal, I have three junkers under the bench but a good one can be a god send and come in handy. I now use it a lot more then I once did, not really needed but I can really dial in an engine and see it happening.