03 chopper makes engine noise runs rough

[Big dog papa]

In 3rd gear at 4500 rpm the motor makes an awful sound like something broke and then started running rough. I pulled over and it ran a few seconds then shut down. It wasn't a single cylinder running sound. Both plugs look good. Pushrods look good. Borescoped and top of pistons and valves look okay. Any ideas?

 

[Sven]

Noise from the top end or lower end? Noise only when in 3rd or only when at 4500 rpm? ''like something broke'' is when it stopped, or kept running with this noise?

First thing I do is check compression or leak-down it. Next is spark at the plugs. Technically, I'd tear it down and not get it running. This might snowball more parts on the parts collection needing what is ''broke'' now.

 

[Mickmorris]

Pull the pushrods and tappet covers possibly a lifter coming apart. You could pull the cam to check this also. When you drop a lifter it usually will show some damage to the cam itself pretty quick

 

[Big dog papa]

Noise from the top end or lower end? Noise only when in 3rd or only when at 4500 rpm? ''like something broke'' is when it stopped, or kept running with this noise?

First thing I do is check compression or leak-down it. Next is spark at the plugs. Technically, I'd tear it down and not get it running. This might snowball more parts on the parts collection needing what is ''broke'' now.

Couldn't tell top or bottom, didn't stop running until I pulled over, then it idled a few seconds then quit, both plugs tested good for spark, yeah I'm with you, not cranking again till I find the cause, thx for your input

 

[Big dog papa]

Pull the pushrods and tappet covers possibly a lifter coming apart. You could pull the cam to check this also. When you drop a lifter it usually will show some damage to the cam itself pretty quick

Raised the pushrod covers and I'm in the process of checking the lifter movement and lost priming of any lifter. thx for your input Mick

 

[knothead]

I'm sure you collapsed a lifter at 4500 rpm

 

[knothead]

Or possibly broke a valve spring

 

[Big dog papa]

Or possibly broke a valve spring

Thx for info knothead,,, I'll check it out