P500 Top Dead Center

[MarineTanker]

Is there an appreciable difference in piston stroke when determining TDC ??
I just did my 100 mile valve clearance check on my Pioneer 520 and determined TDC simply by rotating the crank until the piston was at TDC. However, I've been "told" TDC should be the TDC on the COMPRESSION STROKE, not the exhaust stroke.

 

[Admin]

 

[KyGal83]

I can't help you with this... Someone who can will be along shortly. @906UP or @Neohio ,

But every time I hear someone refer to TDC. I think of this... IYKYK..

 

[906UP]

Is there an appreciable difference in piston stroke when determining TDC ??
I just did my 100 mile valve clearance check on my Pioneer 520 and determined TDC simply by rotating the crank until the piston was at TDC. However, I've been "told" TDC should be the TDC on the COMPRESSION STROKE, not the exhaust stroke.

Technically, yes there is a difference. You should check valves at TDC of comp stroke. Then you are guaranteed that both valves are completely closed. If you check it between the exhaust/intake stroke (180° out on the cam) you may get bad readings as some cams have some overlap or you could be on the ramp down/up of the profile. That said, the P5/P5.2 is a very simple powerplant, I doubt you'll have any issues if you checked it like that.

 

[MarineTanker]

Technically, yes there is a difference. You should check valves at TDC of comp stroke. Then you are guaranteed that both valves are completely closed. If you check it between the exhaust/intake stroke (180° out on the cam) you may get bad readings as some cams have some overlap or you could be on the ramp down/up of the profile. That said, the P5/P5.2 is a very simple powerplant, I doubt you'll have any issues if you checked it like that.

Yeah, my brother (master mechanic for 45 years) told me about this AFTER I did my valve check and adjustment. He basically told me the same as you that he doubted I would have any issues. BTW, after the job, I started the engine and I swear it caught earlier than before the adjustment. Took it out for a ride around, and it's purring. So I think I'm ok.
I really appreciate your response!
Thanks!

 

[Hello_Darkness]

Yeah, my brother (master mechanic for 45 years) told me about this AFTER I did my valve check and adjustment. He basically told me the same as you that he doubted I would have any issues. BTW, after the job, I started the engine and I swear it caught earlier than before the adjustment. Took it out for a ride around, and it's purring. So I think I'm ok.
I really appreciate your response!
Thanks!

If you had adjusted the valves on the exhaust stroke (or overlap) then they would've been very tight when inserting a feeler gauge.

If loosened at that point, they would be very loose on compression and would be noisy as heck while running.

The easiest way to tell if your on the right stroke is to grab the rocker and try to move it. If it's solid, your 180 degrees out and not on compression.

 

[DRZRon1]

Yeah, my brother (master mechanic for 45 years) told me about this AFTER I did my valve check and adjustment. He basically told me the same as you that he doubted I would have any issues. BTW, after the job, I started the engine and I swear it caught earlier than before the adjustment. Took it out for a ride around, and it's purring. So I think I'm ok.
I really appreciate your response!
Thanks!

Did you adjust anything?


Good brother - if only he woulda been there

 

[MarineTanker]

If you had adjusted the valves on the exhaust stroke (or overlap) then they would've been very tight when inserting a feeler gauge.

If loosened at that point, they would be very loose on compression and would be noisy as heck while running.

The easiest way to tell if your on the right stroke is to grab the rocker and try to move it. If it's solid, your 180 degrees out and not on compression.

I'm a bit confused by "grab the rocker and try to move it". How so? Are you talking about turning the crankshaft? I've had a few responders say they don't think there's an appreciable difference between TDC on either stroke on these particular engines. I would hate to take the damn thing apart again just to check. I've run it around after my job and it's purring without any tapping. Actually starts first crank now as opposed to before my adjustment when it took 3 to 5 cranks to fire up, which might just be coincidental.

 

[DRZRon1]

I'm a bit confused by "grab the rocker and try to move it". How so? Are you talking about turning the crankshaft? I've had a few responders say they don't think there's an appreciable difference between TDC on either stroke on these particular engines. I would hate to take the damn thing apart again just to check. I've run it around after my job and it's purring without any tapping. Actually starts first crank now as opposed to before my adjustment when it took 3 to 5 cranks to fire up, which might just be coincidental.

What they mean is grab the actual rocker where the pushrod pushes against - at TDC with the proper clearance - it will move a little since there is clearance -

if u checked it when it was 180 out - the rocker shoulda been solid with no wiggle


did u adjust anything ?


In general - without data - 99% dont check the valves - no saying thats right - rule of thumb is check when noisy - its a Honda - skinny pedal down and send it

 

[MarineTanker]

What they mean is grab the actual rocker where the pushrod pushes against - at TDC with the proper clearance - it will move a little since there is clearance -

if u checked it when it was 180 out - the rocker shoulda been solid with no wiggle


did u adjust anything ?


In general - without data - 99% dont check the valves - no saying thats right - rule of thumb is check when noisy - its a Honda - skinny pedal down and send it

Yeah, I adjusted both valves. Such a PITA to just expose the engine to work on it! Dealer told me it would be a $420.00 job! No way I'm doing that. I'm probably going to leave it alone now until and unless I hear anything tapping.