I’m ether overthinking this, or... TDC on comp stroke

Probably put together a dozen motors, never had an issue. Pretty easy to figure out, but recently I rebuilt the motor in my boat, and it has hydraulic lifters so that was a new experience. Manual was shit, but conventional wisdom was wait for the intake valve to open and close, next time you reach TDC that is TDC of the compression stroke and valves can be adjusted.

Okay, cool. Works for me.

Fast forward to today, and I’m adjusting valves on a 660 single in a quad for a buddy. Every time I do it this way and line up the timings marks, both valves are slightly open, indicating exhaust stroke. If I rotate it once more and line the marks up after the exhaust valves just close, both valves are fully closed, there is some play, and they can properly adjusted.

What gives? Doesn’t he exhaust valves just closing indicate exhaust stroke? Is this a valve overlap issue or am I just getting dumber with age? I know it’s right and everything is within spec, but it just seems backwards.

 

you are turning the quad engine backwards?

 

Overthinking. It's overlap. Exhaust valves close slightly after TDC.

 

So, in the interest of making this simple stupid - when I do the valves on my boat in the spring, wait for the ex valve to close, bring to TDC, and adjust from there?

 

always turn away from the cam chain tensioner

 

No. Adjust them at TDC on the compression stroke. When they’re closed. I’m not sure I understand why you’re confused.

 

Wait, so counter clockwise?

 

I’m not sure I understand either. I suppose that I’m a garden variety ‘parts assembler’ in that I can put a motor together provided I have a decent service manual and some time. I’m trying to learn more. When I don’t have those things, what valve opening/closing sequence should I pay attention to to insure that I’m on TDC of the compression stroke and not the exhaust stroke?

 

Depends on motor, which side you're turning from.

 

If it's an overhead cam engine, you can look at the cams. Whether it's direct actuation or rocker (like your 660 single), the cams will have contact with the actuator (rocker or bucket) on the base circle of the lobe (opposite the pointy end) at TDC on the compression stroke. On a typical motorcycle engine, this means the cams will be at 10 o'clock and two o'clock. On the exhaust stroke they both point down. I don't know what kind of boat engine you have.

 

It's an Iron Duke (2.5 inine 4). It's a pushrod motor.

On the 660, I'm turning it clockwise from the clutch side. Hmm.

 

By clutch side, I mean clutch side of the handlebars, the left. Where the pull start resides.

 

Clutch side refers to side of motor with clutch, not side where the lever is.

 

I don't think I've ever even looked at timing marks setting valve lash. You just need the lifter to be on the base circle of the cam, doesn't matter what stroke it's on, but you can only do one at a time. Most manuals have you roll the engine over just a few times to adjust all of them. That shit takes more time to figure out than just rolling the engine over and adjusting one or two at a time if you catch it on the right stroke.