K&B Sportster 28

[kersplat]

The K&B Sportster 28 I have has a spiral groove on the end of the crank shaft. This is a fair idea for BB engines to keep the fuel from coming out the front bearing too much. It is a terrible idea for a plain journal engine. Mine has the front half of the journal galled from lack of oil because of this :shock: . Do you still carry on with this MFG technique? I love these engines, they are extreme performers for a plain bearing engine and I want another one :D but.... I would hesitate to buy another one if the cranks still have the spiral machined on the crank. PS. I do not use fuel with 100% synthetic oil and because of the good performance these engines put out, I get plenty of thrust @ a rich 10,000 RPM with a 9X6 MAS.

[kersplat]

Is there a K&B tech rep going to answer my question on this thread? :?

[MECOA]

We never have a gauling problem as the sprial doesn't keep all the oil from the front end. Many tens of thousands of these have been sold with this design and no complaints. If it wasn't there fuel would spray out the front.

I believe your problem may be the result of one of two things...

1. Fuel may contain less than 18% oil. Check the percentage of oil by volume not weight.

2. You may be missing the thrust washer behind the prop driver. This is there to keep the reward force of an electric starter from gauling the front of the crankcase. See it here

http://www.mecoa.com/kb/56/sportster.pdf

[kersplat]

In response to your reply, The steel thrust washer is there and I hand start all of my bushing engines. Bushing engines , no matter how they are designed, should never recieve an axial load of an electric starter. The fuel I used was Fox Super fuel (28%) all castor oil. I am a machinist and I build model engines. This spiral on the crank shaft journal of a bushing engine is a problem.

[MECOA]

Sorry but you seem to be the only one with this problem. Since you are a machinist and feel this is a problem grind another sprial in the opposite direction to cancel out the other one. Now if the engine spits fuel out the front end don't blame me.

[Krbtfd]

I am flying a 28 Sportster and was working well but now I find that the engine will run for 3-4 minutes and then cut out. I have changed glow plugs and adjusted the fuel and nothing seesm to help. I bought the engine used and don't have a manual to assist. Anybody have any sugestions on set up or troublshooting.

[MECOA]

Please read this..

http://www.mecoa.com/faq/carb/mixdisk/mixdisk.htm

and

http://www.mecoa.com/faq/carb/debris/carbdebris.htm