blowing oil-evo bottom breather : V-Twin Forum: Harley Davidson Forums

valkdon · 05-23-2009, 09:09 PM

Got a question for the experts. I have a 87 low rider evo motor bottom breather. Last winter I tore her down repainted the motor, jugs, everything. Took the jugs to a hd dealer had them bored. They bored them 20 over, I got new pistons and rings. Did the assembly and disassembly myself. This bike has close to 5000 miles on it and it still blows oil out the bottom vent. I have been told that the rings arn't seated yet. It uses about 1/4 of a quart of oil every 400 miles. This bike did not leake a drop before I did the motor work. How long should it take for rings to seat or is there a fix for my problem? Thanks for any help! This bike has no motor problems other than that.

Woody218 · 05-24-2009, 09:40 AM

If the rings aren't seated after 5000 miles, they ain't ever gonna seat!

valkdon · 05-24-2009, 12:40 PM

I agree with that. I would think the rings are seated by now. The problem with the bottom venters is there's nowhere for the oil to go except the ground. Can't figure out why it is doing it now and wasn't before. Rebuilding the top end is pretty easy and it wasn't my first one.

Dan89FLSTC · 05-24-2009, 03:09 PM

Just thinking out loud here...

Partially restricted oil return line.

Wrong oil filter.

Oil level too high in tank.

Damaged/upside down piston ring.

Crappy bore job.

All can cause oil to blow out the breather.

valkdon · 05-24-2009, 08:39 PM

Oil line not restricted, hd oil filter,oil level has not been to high but I did put to much in before the 400 mile trip, but it was to the level I used to run before the top end rebuild. Noted, I will keep it low and see what happens. Piston rings are right and undamaged (99% sure) Bore job, I didn't do but hd stealer did. I can only assume they know what they are doing. Sick of the oil dripping and will probably get rid of her. Have spent till I am spent out.

Dan89FLSTC · 05-25-2009, 07:25 AM

Evo filters are different than filters for Twin Cam engines, many parts counter guys don`t know that, make sure you have the right one.

valkdon · 05-26-2009, 06:49 PM

running the same filter I was running before rebuild.

Dan89FLSTC · 05-26-2009, 08:17 PM

Is it an EVO filter?

olmate · 05-28-2009, 07:29 AM

99% sure on the piston rings... did you read install instructions for each ring on the packet before you put em on... ie dots or bevelled edge correct way up? I know you said the stealer bored out your jugs but did you give em a nice hot soapy scrub out then one with some petty (gas) and finally a good oily rag wipe through b4 install??

valkdon · 05-28-2009, 07:23 PM

I was meaning 99% on the bore job, it was done at the hd stealership. The rings are in there right as is everything I did to the motor. I am going to do a leak down test if I can find some more info about how to do it.

To Dan 89, yes it is an evo filter, the same one I have run for the last 4 years.

Dan89FLSTC · 05-29-2009, 05:22 PM

Here`s a good home built leak down tester:
http://www.motorcycleproject.com/mot.../leakdown.html

kennyflhr · 05-29-2009, 11:52 PM

If your oil pump isn't scavenging the oil out of the bottom end, it will fill up the case & puke out the vent. Check for sheered keys or maybe worn out pump? Also check the breaqther gear in the cam chest The stock plastic P.O.S. can get pieces of metal or carbon embeded in them & score the case. If this happens,or the breather gear is out of time, you get pressure in the bottom end & oil gets blown out the vent. You can buy over size breather gears & the tool to cut out the damage to the case. Let me know how it goes. good luck.

valkdon · 05-30-2009, 12:00 PM

I had already checked the breather gear, it is timed right. The oil pump is the original pump. It is pumping back to the tank I have checked it by looking in the tank and reving up the motor. If it is worn, will it cause oil to vent out the bottom?

Thanks dan for the leak down tester. I am going to wait after the weekend to do any more testing. Its riding time now.

valkdon · 05-31-2009, 01:05 PM

Decided to go ahead with the leak down test this morning. I borrowed a tester from a friend. I had 1% leak on both cylinders at 100 psi. I could not hear any air coming from anywhere. I had my old lady help and she has good hearing. She couldn't hear any air leaking either. I am suspecting maybe the oil pump or what else is there?

Dan89FLSTC · 05-31-2009, 03:44 PM

1/4 quart every 400 miles is not a lot of oil being used. It looks like you have a good sealing motor as far as the rings and valves go. That small amount could be going past the valve stem seals, which will not show up on a leak down test. Do you still have your crankcase breather routed up to the carb backing plate? If so you will probably notice oil,
especially after you run it hard.