Resolved Crank sprocket vibrates

[syndr0me]

Fidenza lightweight
BS removed.

Just did an engine cleanup on my 6 bolt on my 95gsx. Took the engine out. Cleaned her all up real nice, paineed it. Cleaned the timing components (oil spill) and re timed everything perfectly (except oil sprocket). Engine internals and head were not touched.

I seem to be getting lots of vibration from the crank sprocket ( not the pulley dampener). I took the timing cover off to visual check the belt operation. I can see the belt run true the entire cycle, except for when I look at the crank sprocket. There seems to be a vibration and the sprocket does not look like it spins true (minor but noticeable). I can look at the oil pump sprocket and see it spinning pretty true. But the belt from the oil sprocket to the crank sprocket and crank sprocket to mid way to the eccentric pulley seems to have a little vibrations. As a consequences, the vibrations intensifies/exaggerates when I have the harmonic pulley on, and as another consequence, throws my alt belt (have the GM alt on).

I need to know if I'm being paranoid or this is normal crank sprocket vibrations (torsional whip??). Its driving me nuts.

 

[pauleyman]

Why don't you check runout.

 

[syndr0me]

Why don't you check runout.

Sry, what's runout?


*edit. Wow. Just check the clearance on the auto tensioner to idler arm, it's about half of what it should be (1.8mm)... but the grenade pins slides in and out just fine. And the eccentric pulley "eye" holes are exactly at 10 and 2.

What gives??

 

[BogusSVO]

Worn key way sloppy bore in the crank gear?

Bangged out wouudruff key slot in gear or crank?

 

[syndr0me]

Worn key way sloppy bore in the crank gear?

Bangged out wouudruff key slot in gear or crank?

That's an idea.

However, I just redid my timing tension. Going to give it a shot now since before it was way to loose.

 

[syndr0me]

No difference really.

But I now I hear a very subtle "click click click" pause "click click click" pause. Loudest near the intake cam gear.

This is super annoying.

And I keep throwing my alt belt when I Rev the engine arghrrrrr.

 

[crimsondragon]

What dampener do you have? OEM? Or run of the mill auto parts store? I'd look at the dampener at this point.

 

[pauleyman]

Make sure the crank is actually round. Take the gear of and see if either it or the crank is damaged.

 

[syndr0me]

Must be an illusion. It's the belt vibrating, not the sprocket.

Alright. I found the problem. It's a weak auto tensioner. After resetting it, I found itself sink down to about 1.2mm of clearence. It cause a slight tick tick tick and it vibrates against the idler arm.

I can stick a flat head screwdriver between the piston and idler arm and rotate the screwdriver to make the piston expand to the right specs, but it just sinks to almost nothing after a couple of minutes while the engine runs.

As for the GM alt belt, sucker just kept expanding and expanding and expanding. It's crazy how loose it is now with no tension, as compared to before when it was new, I could barely get it on. It seems to have stretch enough and stays in place now.

Weww. So relieved. Anybody know the cheapest place to get an auto tensioner in Canada? I live in Montreal. I usually order from RTM, but there prices are so high, 176$ + shipping . Eek