Notorious B.E.N.
100cc
It would be under the lever with the arrow pointing to it that says "Pressing here lets more fuel in reservoir by lifting needle." To get to it, carefully (I.E. put a finger over the lever) remove the screw just to the right.
Basic engine tuning.
- Thread starter Terryscustom
- Start date
gyro
GSN Contributor
@Notorious B.E.N. thank you very much for the detailed instructions, I'll try that repair tonite.
Terryscustom
640cc Uber Pimp
I've had, god I don't know how many dozen, engines of all makes models and sizes and not once have I had to adjust the pop-off pressure. I would exhaust all other avenues and perhaps seek further advise before doing this.
Also there are things with the pop-off pressure that play a key roll, such as the height of the little arm holding the spring down. It can be off by very small fractions and change the engine, so adjusting the spring and pressure is not something for the average joe that does not know what he's doing.
Also there are things with the pop-off pressure that play a key roll, such as the height of the little arm holding the spring down. It can be off by very small fractions and change the engine, so adjusting the spring and pressure is not something for the average joe that does not know what he's doing.
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Notorious B.E.N.
100cc
I mean, I understand that the engines are designed around certain parameters but with my 60 I could not get rid of the midrange burble and anytime I went inverted, knife edge, or tried rolling maneuvers, the engine would not respond and lost a lot of power.
So it's either sell it, send it in to DA, or try something. It was obviously a fuel flow problem and someone suggested stretching the diaphragm spring. That got me the idea that maybe the spring was bad. The new spring I got was about the same dimensions and now the engine runs great. Yes I took a risk but the motor runs great in any attitude now.
So it's either sell it, send it in to DA, or try something. It was obviously a fuel flow problem and someone suggested stretching the diaphragm spring. That got me the idea that maybe the spring was bad. The new spring I got was about the same dimensions and now the engine runs great. Yes I took a risk but the motor runs great in any attitude now.
49dimes
Damn I'm hungry
I'm guilty for telling you.... But hey! Your 60 now runs great
. The only engine I had that needed attention in regards to pop off pressure was a used 3W 75 side carb. Would drool fuel when shut down. When I checked the fulcrum for proper alignment to the carb body it was ok so I stretched the spring a tad and fixed the dribbling fuel issue. Engine ran great.
Notorious B.E.N.
100cc
No worries. I guess the main reason why I decided to follow you up on your suggestion was that to me it was obviously a fuel flow problem and these carburetors are mass produced when means there can be some bad/defective parts.
Plus I wasn't the only one with this problem and other people have had similar problems so I started to think that yes DA designed an engine around X specs and they found what worked and released the engine but what about when people with different altitudes and setups run the engine and it doesn't work for them. So I decided to try something and it worked. I also spent one of the test flights at mid-throttle doing harriers and the motor didn't get too hot and was around the correct operating temp so it's obviously getting enough fuel.
And I'll be the first to admit that I have thought several times about sending it in the DA and having them look at it but it runs fine.
Plus I wasn't the only one with this problem and other people have had similar problems so I started to think that yes DA designed an engine around X specs and they found what worked and released the engine but what about when people with different altitudes and setups run the engine and it doesn't work for them. So I decided to try something and it worked. I also spent one of the test flights at mid-throttle doing harriers and the motor didn't get too hot and was around the correct operating temp so it's obviously getting enough fuel.
And I'll be the first to admit that I have thought several times about sending it in the DA and having them look at it but it runs fine.
Snoopy1
640cc Uber Pimp
I probably sound like a broken record
When a rear carb engine runs leaner with the carb diaphragm plate facing the ground and richer facing away I'd suspect weak pop off pressure.
There is a little spring under the level under the diaphragm plate. It's likely too weak causing low pop off pressure.
A small engine shop could set it to 25 ish PSI for you. You could try adding a small spacer under the spring. The spring could be lengthened and tempered a little at a time until the tuning differential goes away. A new stronger spring could be installed.
This all fits your situation in that you are tuning it with the plane upright on the ground which is the richest orientation. So it runs great upright, but flip it inverted with the plate facing the ground and it goes lean.
@ThePledge if I may ask. How did you get the number 25psi. How is that number determined please not questioning just trying to understand. If you can you explain what changes to the carburetor performance as the pop pressure goes up. Thanks.