HIGH-TECH: Husqvarna Motorcycle Won't Rev Above 5k RPM, Won't "Accept" More Than 1/2 Throttle

Could also be a weak ignition system that isn’t generating the voltage it should and refuses to operate over 5,000 RPM.

Well, just opened up the top end and the roller rockers’ roller is missing on the intake, loose on the exhaust. So there is metal loose in the engine somewhere. The cam is a little damaged as well…but possibly usable. I don’t know what I’ll do next, just the rockers, complete rebuild, or what…but thanks for all of the input guys.

As Ray would say, “Sonja Henie’s tutu!”

"The cam is a little damaged as well…but possibly usable. "

Uh, no…

A weak spring (broken spring) will not close the valve at higher rpm’s, basically preventing compression and proper combustion. A single spring that should be part of a team may have enough to close the valve at lower RPMs, but as the RPMs build the inertia on the reciprocating parts (valves are one) overcomes the ability of the spring to close the valve. The torque curve flattens out at that point and the engine can go no faster.

For the record, Rod’s posts need no validation from me, he’s one of a handful of extremely knowledgeable and experienced regulars. You can rely highly on his input. I do.