I have a engine that is about to make me lose my testimony. My ASP 108 will run then quit. I have chased the LSN all over the place. Problem is, I don't know if when I screw it in if that leans it out or not. Can't find a manual on it. I have replaced all the plumbing and did a pressure check under water and can't see any bubbles. Any suggestions. Normally I am pretty good at adjusting engines. But this puppy is getting to me.

Here is a thread with a pic of the "manual" page. LOL

http://www.rcuniverse.com/forum/m_14...tm.htm#1428511

I think the ASP is a clone of the OS 108 so you should be able to read their manual.

http://manuals.hobbico.com/osm/108fsr-manual.pdf

Set up a new test tank system.

Reset all needles to factory setting and try from there.

if your willing to change carps get an OS or Perry carb

Still runs like a dog? Get rid of it. Ebay that sucker. Be honest say you haven't had any luck getting it set so your selling it. Those clowns on ebay "like me" will run the auction up to close to the price of a new one.

who sells carbs for the ASP 108

I like Perry carbs. http://www.perrypumps.com/prod01.htm

Looks like you'll have to call them. "AKA custom and expensive"

Did the engine used to run fine, and now it's dogging you? If it's never run well, or you bought it secondhand after someone overhauled it, one thing a buddy and I ran into is an improperly inserted cylinder sleeve. This was with an OS .55; we were at our wits end getting it to run, and we're both experienced with nitro engines. We sent it back to hobby services and that was the problem: the cylinder liner had been inserted 90 degrees off. The engine would start, run, but not really respond to throttle nor any needle valve adjustments. Take a look in the exhaust port to see if it looks partially blocked. That might indicate a misaligned cylinder sleeve.

It is a brand new engine. Last time it was flown was a couple of months ago. went to fly yesterday and this is when all of the problems started. I know that I have the LSN screwed up and don't know where to start. If it is like my other engines when I turn the LSN clockwise that will lean it out. Not sure this is the same way.

unless I am mistaken..that is one of those motors that has a reputation as being a pain in the butt. I am no glow expert..but a friend is, and he collected some of those motors real cheap, and he never really did get them to act as reliable as nearly any other motor... I recall it was a 1.08, I am not sure ....but I think it was the ASP...

I have a couple of ASP 75's and they run great. This one did also when it was last flown.

Ran great, last time it was flown, now suddenly it's not right?

Sounds like your new jug of fuel is suspect. Try a different jug.

Good luck,
Dave Olson

all magnum two strokes i have delt with (and a few four strokes) take a long time to breakin, the magnum .52 in peticular. the engines run fine above half throttle but between half throttle and idle the engines would die. The first magnum .52 i got so fustrated with, it wouldnt transition worth a darn and would always die on me so i just started running it at full throttle. after 20+ or so flights the engine now runs great, the transition is perfect and the idle is very low.

The key thing i figured out with magnum engines is first off patience, if it isnt running perfect just keep flying it where it will run (aka fly it at full throttle)
second the idle changes EVERY FLIGHT, literally, after flying it at full throttle for 10 or so min the engine is breaking in, less friction means less fuel. Dont try and tune the idle perfectly because you cant (trust me ive tried for hours), just run the engine and after 5 flights lean the idle alittle and repeat. after two gallons you will have a very good running engine

my magnum .52 four stroke was also like this. i have two magnums .46 that have the same problems but to a lesser degree.
and finally my friends magnum .52 had the same problems mine did, just needs alot of breakin time

hope this helps

I had one of these years ago. It's a good engine. On mine, I was tweaking the LSN ever leaner ("in") to get it "better" untill I noticed the high end was getting difficult to richen. What happens is that the LS needle going in too far starts blocking the fuel flow from the HS needle. To get back on track, back out both needles to get a rich run.See that you are able to get slobbering rich on the high end, and then start leaning it a little at a time, HS and LS. Lean the LS untll you get good transition, then stop. Lean the HS for good running, and you are good to go. You should always have the capability to richen the HS, if not, your LS needle is too far in.

I flew my other planes that same day with the same fuel. Maybe it has a leak someplac

If thje poor run persists even after you have the needles back to factory default (particulalry the low needle) yry replacing the glow plug, if you haven't already done so.

I had an ASP 1.8 4S and the first thing it did was leak fuel around the HS needle valve seat. I purchased a new needle valve and that solved the leak problem. The engine contiually loaded up at idle so I changed the plug from an OSF to another 4S plug with a hihger heat range. Problem persisted so I sold the engine. I let the buyer no about the problems. Moral of the story is these engines IMO are only suited as paper weights. The old sayin is "you get what you pay for" and the ASP engine fits the phrase perfectly. If you want a reliable 4S engine than buy either OS or Saito. My mistake.

if you do not give the engines at least a few hours of running i agree they are paper weights, but after they breakin they are wonderful engines, its just a patience deal (and a time one as well)

I brought this engine because it was cheaper than a Saito 1.8 4S and that was a mistake. I tinkered with this engine to long to consider it to be reliable and that is the main reason I sold it. Engine failure at the wrong time is my worst nightmare. My airframes cost to much to be damaged or destroyed by its powerplant.

Go over the basics, is everything clean and tight? No airleaks? Next I'd check the tank. Check ALL the plumbing including the fuel lines. Glow plug good? If that don't work I'd clean the carb. If that doesn't work, borrow a tank of fuel from a buddy. Good luck, let us know how you fair.

I have an ASP 1.08 and am happy with it, although with an OS 7D carb Im not happy with low speed performance, loads at idle. ( I am probably trying to idle too low)I went back to a stock muffler from a pitts style and got improved dependability. Also I tried centering my tank on the carb. I am a big supporter of run it with as many oem parts as possible because it had to work at the factory. My carb change was due to a missing carb when I bought the motor and I had an extra 7D in the drawer. I have one full season on the motor and no dead sticks. Good luck on finding your glitch...

Take off the carb.

Clean it off as best as you can to get all of the glow fuel out that is possible.

Hook up a NEW clean piece of tubing to the input nipple.

Open the barrel up fully and blow through the other end of the hose.

You should be able to get a slow sustained HISS of air with just a little pressure build up.

If not adjust the needles until you do. Note which needle causes the greatest change.


Now close the barrel leaving about 3-4mm of the intake hole open.

Blow again. You should get a small HISS, but it will take some pressure to move the air.

Adjust the needles until you do....

Finally close the throttle all the way down, blow again. NO air should flow.

If you are unable to close the throttle fully, you may have to back out the LS needle ( depending upon design ).

With the throttle fully closed adjust the LS needle until there is no airflow if necessary.


The above should let you find out which screw controls which setting... and it will put the carb into the range where the engine SHOULD start, though the engine will be grossly out of tune.


I use this technique to check other people's problematic engines at the field....

It assures no blockage and at least minimum fuel flows, while identifying how the needles work.

BTW: The screw on top of the carb is NOT a needle screw. It merely prevents the carb barrel from falling out...

The HS needle is the knob.

The LS needle is on the opposite side of the knob as is within the throttle arm circle.

Turn the LS needle out until the head of the screw is almost level with the circle.

That will be an overly rich LS setting but you should get the engine to start to crank over that way.



The manual also says something that is very confusing to newbies....

"The low speed setting is controlled mainly by the idle stop and not the idle needle, which is only used to set the mixture."

Some people read this to mean that the idle stop ( the screw on top of the carb ) is used to deal with the idle, that is NOT SO.

The top screw controls how far the throttle barrel will close, if yours does not close FULLY, then loosen the top screw slightly until it does.

The screw opposite the knob is the idle mixture screw, which must be set to permit flow using the "blow" method.

LOW nitro is key for that engine. I tried it on 10% and it ran lousy! Go to 5% or FAI and see what happens. If you want to run higher nitro you will then need a shim under the head to help reduce compression a bit. Good luck!!

I've had engines go suddenly bad, it was dirt in the carb. Try pumping fuel through the carb at idle and WOT to flush it out. It helped me.

I have a Magnum 52 4-stroke (same as ASP) and I just about gave up on it. I have almost 2 gallons of fuel through it and I have concluded that it is an easy starter, but idle stays too high unless I lean out the LS needle and reduce WOT power. In the end, it will be a basic low power engine. Easy to start, but weak.

The money I saved in the price of the engine, I spent on the extra fuel to break it in (+aggravation). Just run it on the bench with old fuel to break it in (2-gallons from the concensus here).

One thing for sure, it does have compression. I have been using 15% full synthetic. what kind of a shim? I have about 10 gallons of 15% fuel as we buy it by the drum and all of my other engines do well with it.

Good point.

You can push fuel into the carb with a pump directly connected to the nipple, and then quickly reverse it to suck out or dislodge any obstructions.

At worst remove the nipple too and make sure that there are no clogs or debris.