DKD

hi there,

i am having some problems with the engine in my hyper 7 (sirio 27). At high rpms the engine goes very lean (no matter how rich i set the high mixture setting) and at WOT the engine will cut off.

i have replace all my fuel lines and checked the the fuel tank is sealed properly. now have to look for air leaks.

where on the engine should i check for air leaks?

do you have any ideas what else may be causing this problem?

thanx

Super_Dave

Check if your back plate or carb is loose (not just where the carb mounts into the block but also where the main needle screws into the carb body). If its your back plate then fuel would be going all over the place though.

peterman9000

check the carb's fuel nipple for dirt

kidswift

I know someone at our track had this problem and it was the o-ring on the HSN. I would check that

DKD

thank every one, iv used oxygen sensitive sealent on the back plate, carb neck and on the hsn assembly and have use locktite on the engine head i started it up today and still no luck.

im sure its a air leak because as soon as i open the throttle full it dies (go too lean) iv tryed making the fuel mixture very rich but it readly doesnt make much of a diffrence.

any more help?

Da Smak

Look at the Front bearing seal.

Da Smak

Look at the Front bearing seal. Also watch the fuel line for air bubbles. Possibly a dodgy fuel filter or tube.

Super_Dave

Have you checked the fuel tank? The o-ring seals in the cap go bad after a while or if you pinch them the wrong way... it could just be adjusted to loose as well.

DKD

thanx every one im going to do some work on it today, il keep you posted

Super_Dave

GLOW PLUG! I just remember a little while back I had a glow plug that did that to me. It would start and idle fine but when you get to higher rpms the plug didn't have enough heat to burn the extra air and fuel in the cylinder so it would just blow out a puff of smoke and die like it was running way to rich. Just another possibility.

DKD

thanx alot, imgoing to my lhs tomorrow to c if they can find the problem, il buy a new plug and see if this effects the problem.

thanx

rcsrock

hi i have a ofna lx comp and I have the same problem. I richen it alot but still at full throttle it wants to die. How do I check the fuel line for an air leak? Also, any other possicle air leaks? Thanks Anyone can help.

Da Smak

Look at it and if you see bubbles then there's a leak.

rcsrock

I tried replacing the fuel line and that didn't seem to work. Do u connect one end of the fuel line to the fuel tank lid and one end to the exhaust pipe, and one end to the carb and one end to the other needle on the fuel tank?? Just makin sure i did it right. If the fuel line didn't fix the problem what else could it be? Please explain thorughly because i am new to this hobby. Thanks. Anyone comment.

Da Smak

It deffo sounds like the front bearing seal has gone now, Swap the bearing and see if that solves it.

rcsrock

Ok Thanks. where exactly is the front bearing seal?

Super_Dave

If its the front bearing seal you'll see fuel all over your chassis. Air leak can come from loose carb, bad carb seals (in the needles and where it mounts to the engine block), fuel line, loose carb needle (high speed where it threads into the carb body itself), leak in the fuel cap on the fuel tank/primer on the fuel tank if you have one, loose backplate/crankbearings but thats only if you see raw fuel leaking from them, exhaust leak... the loss of back pressure might not give enough pressure to the fuel system, and thats about everything that can cause an air leak that I can think of. If you do have an air leak it will run lean remember just no blue smoke, revs really fast then just die because it staved out of fuel. If you get lots of blue smoke out of the exhaust, very sluggish, and just stalls then its either to rich of a mixture or a bad glow plug that wont hold heat.

P.S. Rock you do have your fuel lines set up right... and the front bearing seal I belive hes talking about is the crank shaft bearing thats behind your flywheel.

Raddick

My Feedback: (1)

Is air bubbles in the fuel line a sign of an air leak? Asking because my new PCR RTR has lots of air bubbles in the fuel tubing to the carb...

Super_Dave

Yeah usually some air bubbles are normal but when you have a lot and its making it run lean that means you have a leak in the fuel filter most likley. Usually nothing else causes air bubbles in the fuel line.