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Ironhead Sportster Motorcycle Talk (1957-1985) For all those that wanna talk about Ironhead Sportster Motorcycles

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  #1  
Old 4 Weeks Ago
Pezed's Avatar
Pezed Pezed is offline
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Default Cam cover

Hooray! I have finally today managed to resize and upload a picture to this forum via mmgb.

Not so good is the reason for so doing......here it is



So, I was riding along, then sudden loss of power. Pulled clutch and coasted off of the road. Loss of compression on both pots, but it was at least turning over on the kicker without any horrid noises. Trailered home and peered down the plug holes, deep joy, nothing amiss there. I now suspected bent valves, and when I popped the pushrods tube spacers, sure enough, number one inlet and number two exhaust pushrods are discoloured brown. Upon removing the cam cover, the small pinion was laying at the bottom front. I cannot see any other damage on any other gears- weird or lucky?
Heads off tomorrow and see what's what.
How is this drive gear normally attached to the shaft, I can see no evidence of any retention mechanism?
If, like me, you are not running a tacho, then remove this item toot sweet and save yourself grief and money.
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  #2  
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I hope everything else is in good shape. My fingers are crossed!
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  #3  
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Pushrods

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  #4  
Old 4 Weeks Ago
needspeed needspeed is offline
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It's clear that there is something wrong other than the tach drive gear coming off. That alone wouldn't cause the engine to lose compression.

If the tach gear got bound between one of the cam gears (it looks like it did) and the pinion shaft broke or sheared the key in the flywheel that could cause bent valves and loss of compression. Another possibility but much less likely is a spun gear on the #2 cam (rear intake). Let's hope it's something less serious. Do the gears turn when pushing on the kick starter? Don't try if you haven't removed the pushrods before removing the cam cover.

Your pushrods look very dry.
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Needspeed, you are correct. it hadn't occurred to me that the loss of compression may not be related to the tach drive gear lying in the bottom of the case. I was looking for a problem, and I found a problem, it certainly has been damaged, and my assumption was that it had got stuck between cam gears and that's what has bent the valves. Before I took the cover off, I was turning the engine over by hand on the kicker, plugs out. I observed the pushrods moving up and down. I had also seen the pistons moving up and down through the plug holes. It stands to reason though, that in order for the valves to hit the pistons, then the timing needs to have got seriously out of synch, and a busted woodruff key would certainly allow that. Thanks for pointing that out.
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