K&B redhead issues

[Rick Raffaelli]

K&B redhead issues

Does anyone out there have any idea how not to break cranks in these things. Stock crank,mod crank,it does'nt matter. Love the power,hate the crank. Please give me some words of wisdom other than get a new motor (like theres alot of choices) or am I just screwed? I think I know the answer but you never know. Rick

 

[Mark Anderson]

Re:K&B redhead issues

Rick

Debur the intake opening. Then work on boat set up so the boat runs smoothly. If the boat hops it will be hard on the engine and cables. Are you running the engine with a pipe or the stock muffler? I had no luck with a pipe, as soon as the motor made power the crank went away. A couple of times in less than a tank full. The stock set up made it two years on the original crank. Beyond that theres not much you can do. Are you using cranks from the old K&B company or the new manufacturer? If they are from the new company contact them so they know there is a problem.

Mark

 

[_laxmasta2039]

Re:K&B redhead issues

redhead issues? hmmmm.....

ah, got one:

-DONT call her hair "carrot-colored"!

lol ;D

Joe

 

[Rick Raffaelli]

Re:K&B redhead issues

The boat runs sweet. Smooth and fast. Irwin pipe,smoothed crank,and 40%. Lake was like glass today,boat scootin right along,then,bluuuuuuck. Looked at my buddy and said broke another crank. That makes three or four,all old stock. I wonder if they'll give me a bulk discount. Would lightening the flywheel help at all?

 

[lohring]

Re:K&B redhead issues

The problem seems to be improper heat treatment as well as rough machining. My latest attempt to cure the problem in my mod engine was heat the crank to 600 degrees in an oven for an hour and allow it to air cool. This tempers the metal to a lower hardness. I then increased the radius of the crankpin end of the intake opening by grinding the opening slightly longer. Don't reduce the seal area too much. I then polished and radiused all the edges and interior surfaces of the intake opening to eliminate stress raisers.

The tempering is the only thing that would be legal for a stock engine. In my experience it helps but is not enough. The ultimate cure would be to buy a Nelson 45.

Lohring Miller

 

[Rick Raffaelli]

Re:K&B redhead issues

Thanks Lohring,I think I'll try the heat treating trick and see what happens. I've already tried all the smoothing,polishing and deburring that can be done. I've still got two more new ones so it's about last resort time. Thanks again. Rick