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Engine Mechanical TopicsDiscussion for motor builds, cams, head work, stripped bolts and other engine related issues. The good and the bad. If it goes round and around or up and down, post it here.
Currently dealing with this and was hoping to get some advice. The picture is of the rear piston 2001 Screaming Eagle engine 96CI? with the dreaded M&M EFI. We installed an upgraded Screaming Eagle hydraulic CAM plate, oil pump and all that jazz along with bigger cams. Got the valves adjusted and everything sounded great. Prior to taking the bike the owner started messing with the M&M setup despite our warnings, minor adjustments but if you have ever tried to tune one of those, you know how difficult they can be. On the ride home they stated that they heard a noise and shut it down. We opened it up and found this along with broken valves. It doesn't look like it was shut down right away to me at all, and I suspect the cylinder ran lean, overheated, detonated and dropped the valves, and then was ridden home on one cylinder, but I'm new to wrenching on Harleys. Any advice here as to what went wrong? How do you prevent something like this when you are doing a cam job? The cylinder head is equally destroyed
You state:
"Installed an upgraded Screaming Eagle hydraulic CAM plate,
oil pump and all that jazz along with bigger cams.
Got the valves adjusted and everything sounded great"
When engine work is performed as described some changes would most times take place.
Was engine timing addressed? since bigger(???) cams installed.
How did you address fuel? since CAM had been changed.
Timing being OFF and a lean fuel condition might make bike prime for engine damage.
Guy, " they heard a noise and shut it down " is pure bullshit, to do that amount of damage that engine ran for a good bit after it blew itself. Had a shovel come through with the same amount of damage, owner swore on his mother's grave he killed it at the first noise. His riding buddy ratted him out a bit latter, said he tried making the 40 miles to home on it.
My money is on a raised redline and they had that bike buried in it when it blew, valve heads don't separate like that under normal conditions even hot-rodding with the stock redline.
If you think you adjusted the valves...you might want to stick with the foreign bikes and skip the Harley's...or you're going to be getting some very expensive engine building lessons. Not saying thats 100 percent on you but as the "builder " it should be on you to make sure some type of tuning happens along with the build before the owner takes their bike. That looks ugly and expensive hopefully you don't get stuck eating the bill on that one.
You change cams without knowing how the motor was built? What was the new cam.. Higher TDC lift and a valve contacts the piston or possibly the 2 valves kiss each other? Not sure you can blame that on a tune.. Detonation typically knocks off the edges of the pistons.. It don't cause both valves to drop.
Last edited by Max Headflow; Aug 18, 2022 at 07:25 PM.
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Blown Piston
