The cranking speed will be somewhat slower than with a 12 volt system, but it should be steady. Try cranking the engine with the ignition disabled (pull the center coil wire or disconnect a primary wire at the coil) and see if the cranking speed stays fairly steady. You should be able to crank the engine for 10-15 seconds without a noticeable slowdown. Also, check the battery voltage during cranking. It should not drop below approximately 4.5 volts. If the cranking speed slows down quickly, and/or the voltage drops below 4.5 with the engine cranking, it's possible your battery isn't up to the job at hand. Have you checked the specific gravity of the acid (assuming you're not running a sealed battery)? At full charge all the cells should be at or above 1.260 and there should not be a noticeable difference between cells.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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