First time poster asking for some help here.

So long story short I took apart the top end of my 96 twin cam motor (stage 1, 50k miles on the bike) because an oil consumption issue and found scored cylinder walls and pistons and a ton of carbon deposits. The engine was rebuilt by the previous owner at a reputable shop with a set of used low mileage cylinders and pistons. Had a hone job and new rings fitted of course. Now this was about 25k miles ago (I have the receipts). So that is a bit weird I think. Now after getting the cylinders out i noticed the crankshaft flywheels are submerged in about an inch of oil so its sumping. Because it's a dyna that can't be due to sitting and oil draining out of the oil tank since the tank is under the transmission thus lower than the sump. So it was sumping for some other reason, I then figured the culprit would be the oil pump not scavenging enough, probably due to excessive crank runout.

Well i took apart the cam chest expecting to find some evidence of pump damage, but didn't find any. I then measured crank runout and it was only .003". All the o-rings where in place and intact, maybe the big o-ring on the pump itself was a little bit hardened but not terrible. Oh and there was a horrible smell in the cam chest and especially the pump, probably due to the sumping and oil aeration.

Now at this point I'm puzzled as to what has been the cause for all this. I originally thought that the damaged top end was due to a failing oil pump (thus also sumping) but now I'm thinking the top end maybe failed first and it's been sumping due to blow by and the oil pump is fine.

Hoping to get some advice on what to check next, don't want to drop a ton of money on cylinders and pistons and have this all happen again...

Thanks in advance.

 

Have you pulled the sump plug and measured how much oil came out? That's the way to check for sumping. Did you notice the engine getting extra hot and any loss of power? It sounds like the rings weren't gapped correctly and or the piston/cylinder clearance was not correct. Just my guess. Sucks either way.

 

so you think yours cannot sump????
wrong.
the pan sump is a special animal. two things that have an influence is riding style and excess oil in the tank.
on these engines if you ride high rpm over a long distance with steady throttle and the oil level covers the riser in the tank, the system can vapor lock and oil flow can be effected. this is the only tank system that hd says that sumping can occur as gravity is not on your side. they recommend that if you do such, that you vary the rpm and make sure the oil level is not too high.
reputable has a wide berth, seen a dude pound on this chest about his greatness and his shop all the while pulling the pinion of an XL engine with a CLAW HAMMER!!!!!
REALLY?????
does he not have the right tools for one and second the knowledge to use them.
needless to say i would not send a schwin bicycle to his shop to have the chain put back on.

 

He thinks it is sumping. That's the opposite of thinking it can't sump.

 

No i haven't but from spinning the crankshaft it's clearly noticeable that it's submerged in about an inch of oil, as far as I know the crank should not be touching the oil at all. The engine was indeed getting hot and that can be seen from some engine parts also (discoloration). Engine had good torque but maybe a little low on power at over 3k rpm. By looking at the piston rings one can tell that it maybe never sealed quite right but I don't see how that could lead to this amount of damage. Front cylinder has quite a deep scratch along the whole cylinder wall. Oh, and both cylinders had good compression before pulling it apart.

 

No, it was definitely sumping. I just meant that the oil in the crankcase now can't be due to sitting for a few months, as usually happens with softails when the oil leaks down into the crankcase due to gravity.

 

there is always going to be oil in th ebottom of the cases.
if you are not havig a performance loss or blowing oil out the breather system, i would think that you are ok. anyway at this point you cant test to much for anythinkg else.
NEVER use used pistons unless they have been professionally measured and approved by a competant machinist!!!!! they are not all equal, one that specializes in HD is best.
the carbon is normal.
m

 

My crank bearings were failing at 70k, cylinders looked ok. But check that rods are not sticky. Dealer said, in Harley fashion see that on 2007s

 

It may simply be the result of the motor getting too hot.. Why was the motor more rebuilt at 25000 miles in the first place. Too much time in traffic? Bad Tune? The guy failed to change his oil. He used amsoil? I've had a 131 ci motor TC sump a few and it didn't hurt anything.

What do the cylinders look like?

How reputable was the mechanic.

 

The PO said it was rebuilt because of a bad tune that resulted in pinging. Bike has been well maintained, no Amsoil though. Cylinders and pistons are bad with scoring and some scratches. The shop that did the work previously is probably the best in my area,