R/C 4 ever

My Feedback: (8)

Hey guys a little help please. My Turnigy 50 engine will not draw fuel to the carb. I have found there is no pulse being produced to power the carb. I changed the bearings thinking the front bearing was leaking but that did not fix it. I inspected the crankcase half’s looking for a crack but found none. The engine has compression. I am out of ideas. This has been a strong running engine for about three years. I am hoping somebody has some ideas about this.
Thank you— Chucko

speedracerntrixie

My Feedback: (29)

Sounds like the pump flappers are stuck to the carb case. Pull the cover with the single screw and take a look at the gasket. It should have two petal looking parts that cover small holes. Those are the pump valves, sometimes when an engine gas been sitting the residual oil will make them stick to the carb body.

R/C 4 ever

My Feedback: (8)

Many thanks for your input speedracer. Actually I am past that point. I did not mention that I had already put a new kit in the carb. That did not fix it so I then installed a brand new carb- untouched by human hands. This also did not fix it. I then removed the carb and sealed the hole but still had no pulse so that totally takes the carb out of the picture. I did not list all this to save on the typing. I check for the pulse by connecting a piece of fuel line to the crankcase tap and putting the other in a jar of water. This shows if the pulse is there or not. I have proved this works by doing this on another engine. On a good engine a strong pulse is produced by a simple turn of the motor even with the spark plug removed. I am now out of ideas. Please don’t give up on this —maybe you can come up with a new angle. Thank you again.

init4fun

Is this a "reed valve" engine? I ask because if it is, a non sealing reed valve could cause what you describe .....

R/C 4 ever

My Feedback: (8)

No it is not a reed valve engine. It has the external pulse line running from the tap on the crankcase to the fitting on the carb.

ahicks

My Feedback: (2)

I'm not sure where your carb is getting it's vacuum signal. It may be internally via a port that can be seen/traced from the carb flange, or it may be externally, via a short piece of vacuum line. Whatever the source, generally it's not hard to verify visually, or with a short piece of wire. Has this been done? Are you able to trace the signal from it's source to the carb diaphragm?

R/C 4 ever

My Feedback: (8)

The fitting on the crankcase is open. I can see through it. As mentioned before it has a external pulse line. I attached a piece of fuel line to the fitting and put it in a jar of water and then rotated the engine and got no pulse at all. It acts like the piston is cracked and allowing the pulse pressure to leak to the other side of the piston thus bleeding off the pressure. I have pulled the cylinder to check for this and all looks well. Doing the same test with a good engine I can see a strong pulse being produced with just one rotation of the engine. I changed both of the crankshaft bearings thinking the pressure might be leaking overboard thru the front bearing but it did not solve the problem.

ahicks

My Feedback: (2)

First, if you do a google search on "Turnigy 50 RC engine, all the resulting pictures show what is clearly a reed valve engine. Yet you say yours is not. That means the carb is mounted directly to the cylinder, right? Please confirm.....

Then, there's this "I then removed the carb and sealed the hole but still had no pulse so that totally takes the carb out of the picture." Please explain. You sealed what hole? The carb opening, or the pulse port? Not following that thought....

R/C 4 ever

My Feedback: (8)

Yes the carb is directly mounted to the cylinder. Turnigy also makes a 55cc engine which is a reed engine. When I mentioned I sealed the hole I mean the hole exposed by removing the carb. Sorry I was not clear.

R/C 4 ever

My Feedback: (8)

Well guys I solved the problem. I think you are going to like this. Seems as though I got hit with a severe case of the attack of the dumb ass. Like i said before I replaced the crankshaft bearings which did ultimately solve the problem however when I put the engine back together I installed the piston 180 degrees out of the correct position. As you are probable aware the piston skirt is cut away by the manufacture on one side only. By assembling the thing like I did that meant when the piston was on the downward stroke the air below the piston was vented into the exhaust port so no pulse was produced—duh. Now that I corrected that the pulse has returned so all is well. The front bearing was leaking the pulse pressure out the front of the engine even though the bearing was fine. I thought about not ratting myself out and just sort of fading away but I decided against it. Thanks to everybody that tried to help.

Truckracer

My Feedback: (19)

A learning experience and we’ve all been there before. Good job finding the problem and correcting it. 👍