Hello ,

I am new to the webra engine and is absolutly a stranger to the MC carb. I have been following the instruction posted by Tony Frackowiak & Jerry Budd over central hobbies website and the help from Rusty, up to today ( after two long weeks trial ), I finally can get it to run at a stable idle speed.
The problem is that I am using Futaba 9c with 5 points curve, and I am having difficulty getting a stable speed at any other 4 points.
I can not tell whether it is too lean or rich whil I am throttling up from 1st to 2nd point. For some setup ( like 8 % of 2nd point), the engine would stay run ~ 20 secs then it stop. That is about the longest time I can get at only 2nd points of the whole curve ( it is getting cold here in michigan and my patience is wearing out). The original straight line set up (0%, 25%, 50%, 75% and 100%) is definitely not working. I can not even get the engine to run over the 2nd point (with 25% setup).
I am not sure should I go much richer like 30, 40 or 50% at the 2nd points.

Any sugegstions and comments are really appreciated !!

If you have experience running this engine with the same setup ( MC carb and Futaba 9c), can you tell me your 5 pints % setup?
I know I may not be able to run this engine with the exact setup as yours , but least it will give me some idea.

Thanks so much !

Mike

A couple of questions, Mike.

Are you running a pump?

What nitro are you using?

Do you have any head shims in?

What plug?

What pipe?

Hi grotto2,

Yes. Perry P-30 pump, Central Header, Greve Pipe.
Cool power 15% nitro. OS F plug.

The pump has the pressure screw about 5 turns screwed out of the pump. Mounted horizontal.
The pressure tube has been replaced with a slightly longer but similar inner dia. silicon tube.

Thanks very much

Mike

Mike-

You will want to run one or two shims in the head with 15%. The engine is made to run on FAI which is zero percent.

I run the pump at the factory setting (mine is .14" out). You should run the hard line that comes with the pump for the pressure line per the factory. A good replacement is K&S 411.

Generally speaking, the throw for the mixture control is about a centimeter. On my radio, the small Futaba wheel isn't quite enough, so I use the next bigger hex arm. Using what you've got, carefully measure your idle setting from some reference point (the firewall for instance) and set the top end 10mm away. You should have 10% or more spare at the ends on your radio programming. Check the direction by blowing through the inlet tube to make sure flow increases with throttle.

That should get your endpoints close enough to go back to the field.

-Ron

Mike:
One other thing - you mentioned you are using a Perry Pump - this engine usually comes with it's own pump in the backplate of the engine. If you have this pump on the engine, and then use the Perry on top of it, you may be flooding the engine. Also, ny experience has been that you must run the idle and lower settings pretty lean to get it to run right, and there are no standard settings, I have this engine in 3 of my planes, and have worked with a number of others in friends and everyone seems different. In fact, if I change an engine in a plane, I keep the original carburator. This keeps all the settings the same.

First of all, I would like to thank you all for all the input !!!

I bought this engine from Rusty. It came with the perry pump amd MC carb. The standard pump has been off. He gave me a good deal for the whole thing (engine, pipe, header and bunch of acces.).

I hope I can run the exact same setting as he did. However, the engine is a bit far from the perry pump when it sitting on my plane. So, I replace the pressure tube with a similar dia. silicon tube. ( this could be the one of the cause) It ends up flooded all the time. Then, I start to screw out the hex adjustment screw ( it is about 5 turns out) of the pump. The flood is reduced after that. I was following the post on the centeral hobbies and the mc instruction and was trying to match the mark on the mixture arm and the location A . It flood badly. It was not working. Then, I start to move the mark on the mixture arm clock wise way pass the location A as the MC manual indicated to lean it. It ends up wiht almost 30-40 degree pass A. However, the engine can be started and idling for a long time without stop. I am using two HS-55 servo with larger servo arm which come with the servo. I setup the mixture linkage on the farthest hole on the servo arm, while for the throttle arm, it is in at one hole closer to the center of the servo. I follow the instruction from the Central hobbies post.

I believe it is a decent engine from Rusty, just my experience is limited for this kind of the set up. I would like to know how you guys setup the mixture curve from point to point. I throttle up (from 1st point ) by one click and one click and then pose to see if the engine can stay run or die. If the engine die then I try to lean it a bit and start it overall again. If it last longer, I keep going to lean it. It it reverse, I will go ricker. Man. It is about 50 degree now in michigan these few days. I do not know how much patience I have had left... The way I did definitely might sounds stupid to you. But I would like to learn the right way from you guys. Thanks so much
Man, it is cold. Got to have something like moonshine now..

Mike

Mike-

I'm sure you find this all very confusing. Setting up these things can be a real trick, especially when you have a used engine, because you never can tell if the arm has been moved, or even put on upside down so it works backwards. That's why I recommend blowing in a fuel tube connected to the the carb nipple while cycling the throttle lever. At the low end you can hardly blow through it and at the high end you can feel a definite flow.

So to reiterate, you idealy would have your radio programmed so that low throttle is at 10% and high end is at 90% with a straight line drawn between those points.

For the mixture arm, the low end should be at the point you measured before. The high end should be 10mm closer to the firewall assuming the mixture arm is pointed toward the bottom of the engine.

When you go to the field, get the top end right first and adjust your straight line accordingly. You should be pretty close then, maybe good enough to fly.

-Ron

thnaks Ron !
I am going to give it a try this weekend.

Mike

Finally, the engine is ready to go !!

Here are the probpems I found. I took the engine apart, and found the rear bearing is all rusty. It is really nasty. So, it took me a while to clean it up really good. Other than that, The small o ring in the MC carb has been wear out which has cause the leaks and that is why I can not locate the true "no fuel" point. I also replace the perry pump which comes with the engine with my as new one. The pressure tube has been replaced with the original one. Two head shims have been added into the engine as you suggested. I use OS F plug and cool power 15%.

Engine starts out right away. It took me about 2-3 hours to tune the whole throttle curve.
The weather is getting colder and I believe it still needs to be fine tune a bit.
Anyway. This is a good lesson learn experience for me. These info. might be useful for the webra MC carb. begining user.

Thank you all again.

Mike