3.5ss @ full throttle

[paullie]

I am having a little trouble with my 3.5ss K&B. The motor usually starts just fine, but after i get it out on the water and run around at half to 3/4 throttle for a few minutes I try to run it @ full throttle and it dies, pretty much instantly. I have tried to increase the throttle gently and also pushing it wide open quickly, both don't work. I am pretty sure that that I am not running it too lean, I would really appreciate any help.

Thanks,

Paulie

 

[topfuel443]

Sounds to lean to me, Paulie. Try richen it up a half or quarter turn and then work your way back down. It should run like crap(really rich) on the stand and then lean out properly once it hits the water and gets put under a load.

~ James

 

[Jerry Dunlap]

Paulie,

You didn't mention what prop you're using. Too big a prop can cause the motor to bog. If you are using a prop no bigger than an Octura X440, than you probably are running too lean at time of launch.

Jerry D.

 

[lohring]

I second the lean comment. I was just doing some testing with my K&B ss, and I needed to open the needle lots from the stock muffler configuration to the piped setup I was running. The boat would go about 400 feet then stop. Otherwise everything seemed fine.

On the stand, open the needle to the point where, when you give the engine full throttle, it won't come up to full rpm. Then close the needle a little until the engine will slowly clean out and come up to maximum rpm. Be careful not to really let the engine wind up or you will fill it with broken rod pieces. This should get the needle close.

Lohring Miller

 

[Jerry Dunlap]

One other thing,

Prop depth can also cause a motor to load up and stop > . On my K&B 3.5ss powered tunnels, the center line of the prop is at least 1/4" above the bottom of the running surface. This will vary with different hulls. But, running the prop to deep won't allow the engine to gain top performance.

JD

 

[snowdog-2112]

Ok,

I like what Lohring said however, beware that this method is NOT recommended for newbies.

I would recommend getting the needle to where he described and then toss the boat into the water as this is the REAL test.

The speed should be slow with no power but the engine should continue to run. Bring the boat in and lean it down. No more than 1/4 turn at a time. As the rpm's come up, your adjustments become more critical.

Once you feel the boat is running 30-35 mph, adjust your needle in only 1/16-1/8 turn increments. As you get close to optimum, you will notice a speed and power increase. A good test to determine if your needle is right is that you toss the boat and it runs through your entire tank of fuel without dieing. My experience, thanks to a very noteworthy and long-time tunnel racer, is that the K&B "ss" engines will lean-out after they heat-up and if it leans too far past optimum, it will quit.

Keep in mind, that when in the "racing zone" of an R/C engine, your needle setting is critical and going too lean could ruin your day. Some people I know add castor oil to their fuel because they do run "just-on-the-edge" of disaster.

Hope this helps,

Snowdog

 

[Gattorno]

I have the same problem with my K&B 3.5 ???

the engine go faster instants a few seconds and turn off, I open 1/8 - 1/16 turn the engine a full throttle not turn off but engine no go faster.

what can i do? ???

Gattorno.

 

[dalbro]

CHECK THE SPRAY BAR IN THE CARB,MAYBE ITS NOT CENTERED JUST RIGHT.