Perry pump with K&B red carb?

[jstew0903]

Perry pump with K&B red carb?

I am new to nitro outboards. I have a K&b 3.5cc outboard. I got the 3.5cc and it has the exhaust passage opend to one long hole instead 4 tiny small ones. The problem I have when I run the boat is I can run flat out for about 2 seconds and then the engine just peters out(no offense if you are reading this and your name is peter!!). I put a piece of balsa in the exhaust to restrict it a little and this helps, It will not peter out as fast but does loose top end power. I am also using 15%nitro by the way.

Now to the my topic. I have rc airplanes and have used the perry pumps on a engine and it worked great. I bought a red carb for this engine( tried the black carb and it does the same thing). Is the red carb and airbleed carb or can I use a pump with it. In the perry pumps instructions it says to use with a carb that has a low end and high end needles. If anyone could help with this problem it would be greatly app. I have check the entire fuel tank and hoses(no restrictions or blockage). I also am running a piggy back tank that aout a half inch lower than the carb. If you have any other advice to make it beat my buddys 7.5cc lapcat let me know

Thanks for the help in advance!!

Jason

 

[Propjockey]

Reerry pump with K&B red carb?

According to K&B's exploded view of the carbs, the only difference in the carbs is throat diameter. Don't know if that helps with the pump idea, but when you get it figured out, run some 40% nitro--your K&B will thank you!

 

[Ron Olson]

Reerry pump with K&B red carb?

Is it just running too lean? The needle should be in the neighborhood of 3-1/2 turns out. The exhaust may have been modified to reduce back pressure. That could be why you aren't getting enough fuel pressure to your tanks too. You shouldn't need a Perry pump. The K&B .21's love nitro, up to 60% with 20% oil, don't use plane fuel. Let us know what hull you have this motor mounted on.

 

[jstew0903]

Reerry pump with K&B red carb?

I thought it might be lean, but I would give it about a half turn out and it would flood and load up. When I get the boat back in, I have to place my finger over the carb vent. to get fuel back in the carb.

I am running a Hydro Sport Marine Whistler 3.5(attached pic). Are these hulls any good? I picked it up on ebay for 25.00.

Maybe you can help with another problem. When I turn the corner sharp it will submarine underwater. I trimmed the engine up quite a bit and it still does it.

 

[jstew0903]

Reerry pump with K&B red carb?

pic didnt post ,trying again

 

[jstew0903]

Reerry pump with K&B red carb?

Front view

 

[Propjockey]

Reerry pump with K&B red carb?

Is the turn fin at the balance point?

 

[Richard Beals]

Reerry pump with K&B red carb?

Ok.. Here is what to do..

1. Inspect your tubing very carefully.

2. Take your tanks and put them under water (kitchen sink)

Close on tube, Blow thru the other. if it bubbles.. there is your leak.

3. No bubbles.. Take a very close look at the carb. All the parts where air can get in.. If this is OK.. take the carb apart and make sure there is no debris anywhere in the fuel flow.

4. If this is not it.. Then you took away too much backpressure when the bottom end was opened up.

Drill the hole in the pressure nipple out to the next size larger.. Make sure the pressure needle has not restricted in any way..

5. Also check you water flow.. make sure the head is getting water flow..

6. Prop down.. you may be turning too big a prop or the engine is too low.. a X-440 is a good prop to run.

7. When you are running K&B carbs you have to be rich in the low end.. So when it cleans out, you don't lean out.

Good luck.

 

[Jerry Dunlap]

Reerry pump with K&B red carb?

Jason,

You might want to consider installing "Stumble Blocks" to the front of the tunnel floor. Look in the posting "Edges and Wings" at GTR's post of the underside of his tunnel boat. Those blocks in the front of the tunnel floor help prevent the boat from stuffing in a corner. On a 3.5 tunnel, the blocks are usually about 4" in length, 1" wide, and come within an 1/8" of the bottom sheeting of the sponson.

Jerry Dunlap

 

[Jerry Dunlap]

Reerry pump with K&B red carb?

Jason,

Beating a 7.5 boat with a 3.5 boat is going to be a BIG CHALLENGE!!!

Jerry D.