My 1988 Evo Softail has a loud, intermittent tapping noise coming from the inlet valve area in front cylinder when warm. It's metal on metal and last for 6-10 seconds, goes away for 30 seconds or so. Doesn't do it when cold, or when you take the revs up from idle. Mileage is about 50,000.

I've replaced both rocker arms and shafts, and made no difference. Someone suggested small end bearings but that would be a constant noise on idle. Last winter, I lapped in valves with new seals, and replaced rings, and decoked the heads.

My bike has solid lifters, not hydraulic, and adjustable pushrods. I've adjusted the pushrods so they just rotate on tdc. Pushrods aren't bent.

The noise is definitely at the inlet valve area, but could it be the lifters, with the tap-tap resonating up the pushrod? I've done the 'screwdriver in the ear' stethescope deal, and it's loudest at the top end.

Help! I defer to your collective superior knowledge!

Steve

 

Does that spark plug or exhaust pipe show any signs of oil? Could be a bad valve seal letting oil bake onto the hot part of the exhaust vavle stem and hold the valve open a little. Does it smoke at all on deceleration?

 

No smoke at all, even on start-up or over-run. Plugs are both clean. Keep 'em coming!
Thanks,

Steve

 

I would lean towards lifters if you've rebuilt the head...I've seen where the bearings in the lifter rollers let loose and will tap ungodly, then go away and come back randomly.

 

I agree, I would look at the cam bearing also.

 

Thanks, guys. Will investigate this weekend and let you know how I get on. I haven't gone into the engine other than doing the heads and rings. This means cam cover off, pullers, and more? Is this a job for the mechanically-challenged, or is it step-by-step and don't lose your nerve?
Steve

 

.............and I would install a set of H-D hydralic lifters while your at it.
No need for a solid lifter in a modern street engine whatsoever.
Scott

 

Hi guys,

Thought I'd check pushrod clearances again, both when hot and cold. Same result. I've got a Clymer manual so will have a go this weekend, and I will get hydraulic lifters. Could it be the small end bearing? Someone thought so. Isn't it odd when you work on your bike, put it back together and then find other things that now don't work! Speedo, right indicator and front brake switch. Arrrghhh!