jaav

This is the reason why you should bench run an engine 1st...Saves the airframe..

mike31

My Feedback: (67)

Low speed needle probably needs to open some. Try closing it and then blow into the fuel inlet using a piece of fuel line. All while maintaining pressure start opening the low speed needle until you hear air escaping. Then open it about 1/8 of a turn more. this will get you going assuming your high speed needle is open enough to run the engine. Adjust accordingly from that point.

jester_s1

Have you checked for an air leak out of the front bearing? I had an Evolution that wouldn't draw fuel and ran erratically and found that there was almost no sealing at all. The rear bearing had not been pressed on far enough at the factory so the crank was set back enough to not seal. Even if you don't have any muffler pressure coming in, the carb vacuum should draw fuel well enough to run on the bench once you're started.

goirish

You got it. Thanks for the reminder.

goirish

I will send you my address so you can send your check to me. Only kidding. I am putting it on the bench and hook up the vent line to the nipple on the backplate and see what that does.

TimBle

bench running an engine is not always the best way to set it up and run in. Bench running often introduces vibration that the engine would not see in an airframe. I always run my engines in on an airframe before flying them. Save for a troublesome O.S. 91FX (notorious) they all run just fine and reliably.

blhollo2

My Feedback: (278)

problem is that you bought an ASP.

goirish

blhollo2

Be Nice.[8D][&:][8D]
Just po folk here.[sm=cry_smile.gif]

teeceeveecee

How About The Clunk ?

Sorry if I missed it in reading post's- I didn't see what type of clunk was being used. If it is the pourous bronze type they can have microscopic blockage. The fact that you get very little fuel flow when you have the fuel line disconnected at the carb eliminates all problems at the engine except for one- 1)Exhaust pressure.

The fuel tank position, the length of tubing, are not factors in getting fuel flow TO the engine. You have demonstrated the problem by turning the engine over with the line disconnected and turning the engine over by electric starter and getting very little fuel flow.

I am not a 2-stroke guy but two things come to mind. If this engine has a cylinder liner is it possible the porting is not lined up or reversed ? Another possible fix would be a check valve in the exhaust pressure line to maintain tank pressure. I use them in many of my 4-stroke applications it helps maintain much smoother running by providing constant tank pressure. Re the crankcase nipple, isn't that just venting ? Remember on downstroke there is crankcase pressure which creates the bypass pressure to force fuel/air mixture into the cylinder and on upstroke creates vacuum to draw fuel in- don't think it would be appropriate for fuel tank pressure.

One other stupid question, you mentioned you are using a three line system. You are capping the extra vent line aren't you ?
Good luck,

Tom

757jonp

My Feedback: (48)

Pressure fitting on the back plate? If it's open to atmosphere, doesn't your crankcase pressure suffer? I'd plug that, use muffler pressure and try again. I'd be looking close at the L/S needle to make sure it's far enough out.

Speedy-Gonzales

My Feedback: (202)

The mention of using the crankcase pressure nipple should be taken with some caution. Straight Crankcase pressure is overwhelming when supplying pressure directly to the tank. Usually when tapping the crankcase for pressure it is accompanied with the use of a regulating pump ( i.e. Perry/Conley or Cline ) where the pressure can be regulated. Usually no more than 2 psi.
Here is my suggestion:
Put a good O.S. .60 size carb ( preferrably a 7D ) on your ASP 108 and see if it will run correctly. Just make sure the carb neck is a snug and correct fit to avoid air leaks and make sure there is a o-ring on the carb neck for a good airtight seal. If it does run correctly...take that ASP carb to the nearest trash container and bid it farewell! I have had several ASP engines and swapped the carbs out on every single one. The ASP engines are good engines but their carbs are questionable. Some are good and some are bad but they all seem to become erratic ( not hold a setting ) with use quite quickly.

SPEEDY

Phoenixangel

people that do not read everything and just post crack me up

js9467

My Feedback: (1)

Is it a ASP 1.08 Red Head? I've got one sitting on the bench that I would part with cheap. I've bench tested it and it seems to run fine..

AJRCUSTOMCRAFTEDRC

My Feedback: (70)

hello i have found with my asp's that most of my trouble has been the back plate leaking air and will not hold case pressure, besides that most of the carbs are crap! i use perrys and never worry again. great motor otherwise..

Speedy-Gonzales

My Feedback: (202)

YES!!! If the pressure nipple on the backplate is not being utilized it should definitely be plugged. 2-cycle engine do not run with a open hole in the crankcase!!

goirish

It is plugged with a original rubber cap. I took it off to see if I could get pressure to the tank. I could get fuel to come out of the carb line when I was turning it over by hand. When I hooked up the electric starter then I did not get any fuel. This was a used engine and the person said it run great. how do I know if the liner is in backwards?

jaka

Hi!
Are you running the correct fuel???
Not more than 5% nitro!!!

teeceeveecee

Look into the exhaust port and see if the liner and the cylinder ports appear to line up corretcly. There will be some overlapping but it should not be significant. If it is, then you would want to inspect further which of course can only be seen properly with the head off and piston at bottom dead center. Then you will be able to see transfer and exhaust ports.

Tom

Phoenixangel

Exhaust port should look like this.

goirish

YUP it does. Normally I am pretty good with engines. I do most of the tuning for our club. But, this thing has me stumpedddddddddd.[:@]

Firepower R/C

My Feedback: (10)

I don't think this has been mentioned yet, but you may want to check the pressure nipple not just for tightness, but for a crack... these are hard to find sometimes and can cause you fits.

teeceeveecee

goirish:

This is really a tough one. Phoenixangel gave us a pic of his exhaust port which is exactly what you should see in yours which you have confirmed. All of the input on malidies with engine really talk to the problem AFTER the engine runs and will sustain the run. Your problem is with getting fuel to the engine. It can only be tank pressurization.

You mentioned earlier the muffler was not the same as your other 108, if possible try swapping them. Maybe the nipple placement in this one is seeing some kind of internal turbulence in the muffler shell that is interfering with full pressure on the nipple. You said earlier that blowing on the exhaust to muffler line did produce good fuel flow so nothing is wrong from the tank on. I would still try the check valve in this line.

Aha- another light bulb just lit up. How large is your fuel tank ? Possibly the volume of the tank doesn't allow full pressurization before the engine dies.

Tom

marvmattporsche

My Feedback: (60)

I would also check the carb where it connects to the intake. I had one that was sucking air and ended up replaceing the entire carb... Good luck

tony0707

HI
open the carb and prime itif it runs on a prime and stops you have a fuel draw problem-try opening the the low end and the top end ( USUALLY 2 1/2 turns on both to start )you may have some dirt in the needle barremove the needle valveand use a thin piece of wire to loosen the clogpull the fuel line and squeegy fuel through the nipple out the nv housingif air is leaking into the engine from any locationyou will not be drawing fuel into the crankcase as you should be- tighten down all engine bolts if you have an air leakyou must find it or the heat that is created from it can and might have a damaging effect on the engines internals from a lack of lubrication-change the glo plug -just my .02 cents flying -GLO- for 26 years-more than mostless than a fewBEST REGARDS TONY

goirish

Ordered a new carb and replaced it yesterday. No Joy. Some talk about the carb may be plugged, but, I can take the line off of the carb and turn the engine over and no fuel.