iniviate

a little while back i hurt my motor.... spun a bearing.

i didn't change anything in the motor. just turned the crank, new rings, & bearings. while it was out, i added a canton oil pan and a street twin clutch. the motor is internally balanced.

cranked it up and went for a drive.... it's got a rather bad vibration. it's in the motor/clutch ..... i just can't figure out where to start.

i took the weight off the back of the street twins flywheel. i read on here that would give it a "0" balance.... which is what i should need.

the motor has ~40psi of oil pressure at 1000rpms and climbs with RPM..... just like the last motor did. it's the same oil pump as the last motor.

the knock sensor is reading 0 the whole time... even if i get on it. when i hurt the motor before, the knock sensor wouldnt stop pulling timing, even at idle.

where do i start troubleshooting?

thanks in advance....
chris

iniviate

btw - i already pulled the transmission and checked the pilot bearing, and everything else. i even started it with the transmission out, it's still got the vibe....

JSK333

It could still be the clutch assembly.

When I had my Street Twin's flywheel match-balanced to my stock one (since my engine is stock, externally balanced), the balancer noted that the pressure plate was also off by a few grams. They're mass-produced by Valeo, so I wouldn't be surprised if yours is off too.

I'd take the clutch assembly to a balancer and have them neutral balance the whole assembly as a unit, since your engine has been converted to internal balance.

iniviate

yeah, i'm leaning towards pulling the flywheel off and having it balanced.

so that's pretty much everyones opinion? start with the flywheel?

96z

Yeah make sure that is balanced, just taking off the weight really doesnt make it balanced....start there.

It wouldnt by any chance be your motormounts would it?

iniviate

ok... so i got the flywheel/pressure plate balanced.

they were both off. the pressure plate was off a lot....

go back and install everything..... there's STILL a vibration!

WTF do i do now?

95 Z/28 LT1

Are you 100% sure it's not ignition or fuel related?

RichJ

What about your harmonic balancer? Is it still weighted for an externally balanced motor?

iniviate

if it is... it's like no other problem i've ever encountered.

i've pulled all the plugs/wires. they're good. fuel pressure is normal, everything looks good, no codes, drives like it always has... plenty of power & throttle response. it's just got a vibe.

heck, i got pissed off yesterday and ran out 4th gear to 7k rpms. it's got more power than the old motor had. i would figure if something internal is wrong, it would have come apart then.

it is much much less than before i had the flywheel/PP balanced, but it's still more than is acceptable.

it's the same balancer ive had for years. i gave it to the balancing man way back when the whole thing was balanced the first time.

i'm going to take it off tonight, just to see what happens... i'm pretty much lost as to what im doing now.

RichJ

This happens when you have it in neutral and rev the motor too, right? I assume that you've verified that it's the motor/clutch and not anything further back like the tranny, DS, etc.

iniviate

correct.

i've even had the transmission out and laying on the ground when it does it....