Advice needed with assembly on an ASP .40 - RC Groups
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Oct 17, 2011, 11:11 AM
Too much power is just right!
ABADGTP's Avatar

Advice needed with assembly on an ASP .40

I have an ASP .40 was all gunked up and it had no compression. I dismantled it, cleaned all the parts up real good, put it back together and I can tell I have compression now but it still wont start. This is the first engine I took apart that had a Cylinder Liner. I am thinking it wont start because I assume I have the Cylinder Liner in wrong. I did not think to take note of how it was positioned when I took it apart.

Can anyone help me? Do you have any pics or assembly instructions by chance? Thanks in advance.

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Oct 17, 2011, 12:05 PM
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ChillPhatCat's Avatar
The cylinder liner really can only go in one way, it needs to have the exhaust port match up to the exhaust outlet on the cylinder in order to run.
Oct 17, 2011, 01:26 PM
Too much power is just right!
ABADGTP's Avatar
Originally Posted by ChillPhatCat
The cylinder liner really can only go in one way, it needs to have the exhaust port match up to the exhaust outlet on the cylinder in order to run.
Technically, it can go in there any way (as long as the lip of the sleeve is at the top of the engine of course)..there is nothing that prevents it from going in wrong and spinning completely around. This is the first sleeved motor I put together so I just put it in and lined one of the sleeve holes up with the exhaust port.

I know what you mean though, there is only one way it can go in there and work. I think Google was my friend because I was able to find pics on what the ports on the sleeve look like when looking through the exhaust ports and I lined the sleeve up according to the pics I found. I only had one sleeve hole showing and it looks like there should be two...equally spaced when looking in the engine's exhaust port. I never found anything for that motor showing proper placement though so I still do not know if I have it right.

I tried to start the motor again and now it has great compression but still wont start for some reason. Before the adjustment, it had ok compression. Before cleaning the engine, I had no compression.

Its probably something simple I am overlooking but really driving me up a wall. I know my glow starter works and the glow plug is glowing, My 12v battery is charged 100% for my cone starter. I read you need to adjust the carb by turning the screw to adjust all the way in and back out 1.5 turns. I tried at 1.5 & 2 turns out...nothing.
Oct 17, 2011, 04:52 PM
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ChillPhatCat's Avatar
Hard to say without seeing it, maybe there are multiple alignments that have an "open" exhaust port? There should be at minimum, a port open to the exhaust, and a port open down into the casing to draw the air/fuel mixture into the combustion chamber. If you have these two requirements fulfilled then the liner is correctly seated. With good compression, a good glow plug and the needle 2 turns out from closed, it should fire up. I'd look for leaks in the fuel line or tears in the carb o-ring. Also, do you prime your engines before trying to start? If all this fails, you can try starting it at full throttle to see if it's just a low speed needle issue.
Oct 17, 2011, 07:53 PM
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coriolan's Avatar
The exhaust port his higher and opposite the transfer port,the two boost port are lower than exhaust and a bit higher than transfer. By "won't start" do you mean doesn't do anything or run for a few seconds and die?
As you can see on that picture there is a notch on the sleeve's flange which should fit a locating pin in the crankcase.
Oct 17, 2011, 08:19 PM
Too much power is just right!
ABADGTP's Avatar
I will try to get pics up later. I will just sit and starting sputter. Howevwr, every once in a while when trying to start it it will just sometging got stuck...maybe like a vapor that possible with rc engines?

I found some pics on a few different .40 engines and some show two exhaust ports equally spaced (when looking through the exhaust port) and other pics show them offset. I was never able to find an ASP .40 assembly diagram or an actual pic looking inside of this engine. If anyone has an actual pic...that woyld be greatly appreciated!

On another side question...can you use the carb off one brand of engine and use it on another brand if it fits? Thanks again all!
Oct 17, 2011, 08:47 PM
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ChillPhatCat's Avatar
You can use different carbs, it isn't recommended though unless it's been shown to increase performance. Putting too small of a carb on it would reduce power and fuel consumption, putting too big of a carb on will destroy it's mid-range performance and increase fuel consumption.
Oct 17, 2011, 10:25 PM
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downunder's Avatar
Most engines have 4 ports cut into the side of the liner. The port that's cut straight in is the exhaust while the other 3 will be cut at a steep angle pointing up and these are the transfer ports for the fresh mixture. The top edge of the exhaust port will be a little higher than the (inside) top edge of the other ports too. Sometimes the exhaust port may have a bridge in the centre making it look like two ports but that's usually only done if the piston has a ring.

As coriolan mentioned, almost all engines have a tiny roll pin set into the crankcase where the top of the liner fits and that notch in the top of the liner to fit around the roll pin which means the liner can only fit in one position. I have a Magnum 40 which is similar to an ASP and it doesn't use a pin to locate the liner. I've found that the exhaust port in the liner needs to be aligned exactly with the exhaust port in the crankcase because even a couple of degrees misaligned allows for leakage between the exhaust and transfer ports. The main thing you'd notice is that it won't prime (draw fuel from the tank with your finger over the carb). The second thing you might notice is that it won't run because it's losing crankcase compression out through the exhaust. A simple way to check is to lay the engine on its side with the piston at TDC, pour a bit of fuel into the exhaust then turn the prop to bring the piston back down. If you see lots of bubbles coming from one side of the piston into the exhaust port then that's where it's leaking crankcase compression and the liner needs to be turned slightly in that direction. Repeat until the bubbles stop.
Oct 18, 2011, 06:29 PM
Too much power is just right!
ABADGTP's Avatar
OK, here are a couple pics...I dont think I can get the sleeve any more centered. Does anyone have a manual or assembly diagram of this engine or any engine that is assembled with the same parts? Any engine regardless of size...if it has parts that go in the same place as this engine...I can be sure I have everything in the right place. This wasnt running when I got it so I am just ASSUMING everything is there.

Also, as a starting point, I turned both high and low needles all the way in and backed off two complete turns. Is that right...then tune from there? I have not tried to start it since I did this. Thanks in advance again everyone.
Oct 22, 2011, 08:26 PM
Your good with the liner orientation in the picture. You will also be good with that HS needle setting if you are running muffler pressure to the fuel tank, use more if your not. I have run into problems with some ASP/Magnum carbs where they usually call for 2.5 turns on the LS needle at wide open throttle. When you then rotate the throttle barrel, it reseats on the LS needle and stops at about 1/3 open (makes for a darn fast idle). What I found that works is to hold the throttle barrel at the idle position or just closed, seat the LS needle, and back it out 1/2 to 3/4 turn.

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