Need some advice : oil blow by!
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Tourer
Joined: Jun 2012
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From: Maryland
Need some advice : oil blow by!
Ok here's what I have, a 1998 dyna wide glide that was fine untill last October it started leaking oil from the front cylinder head rocker gasket while at OC bike week. I had Seaford HD fix it that week and it was fine for the duration. Rode some more later in the year and some over winter with no problems. Earlier this year I went for a weekend ride back out to OC and now it started blowing oil out of the air cleaner, it was all over the right side of the bike. I get it home and it seems to be only the front cylinder with the blow by problem. I had put clear hose on the breather's outlet ports on the heads to see this. My first thought was the umbrella valve in the front rocker not sealing so I take the top and middle rocker boxes apart to inspect but found nothing wrong with it. While I had it apart I installed all new gaskets and seals but also installed the oil slobber fix in the center rocker boxes. Got it all back together and routed the breather hoses to away from the air cleaner to the left side and put a small filter on the end of the hose. Went for a ride and I've still got excessive oil blow by from the front cylinder. What am I missing? Could the bottom rocker gasket be the cause? Before Seaford HD replaced it all was fine! Before you ask about oil level it is just above the low mark and hasn't changed much if any at all. Motor is stock on the inside and the outside just has the basics, Vance & Hines pipes, Mikuni carb & intake. Thanks in advance for any and all help you'll can give.
Seasoned HDF Member
Joined: Jun 2010
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From: Upstate New York
In my case, when I tore down my rocker boxes, I found that the portion of the gasket that separates the breather chamber from the rest of the rocker box had slipped out of position during assembly, allowing oil in the rocker box to overflow into the breather chamber. It's easy to get this wrong on assembly, as there are no ribs to hold the gasket in position in this area and prevent the gasket from extruding sideways when the rocker box screws are tightened down.
I reassembled everything, using the latest Harley gaskets (the white silicone rubber ones), and I have had no oil carryover since, and I run my oil level "topped off."
I reassembled everything, using the latest Harley gaskets (the white silicone rubber ones), and I have had no oil carryover since, and I run my oil level "topped off."
Road Warrior
Joined: Apr 2007
Posts: 1,952
Likes: 15
From: Senoia, Ga., by way of Miami, Fl..
So, I've come to the conclusion that its somewhat normal.. Others will surely disagree, but on both my Dyna and Ultra, they will slobber oil out the breathers. However, its only during high rpm cruising..
I notice it after running the interstate, about 3400(80mph) usually about an hour.. I've installed a Kuryakyn breather with a top/center outlet, allowing gravity to assist as much as possible.. I also run a hose from there, up the backbone and down the front frame legs to vent.. I also tried the slobber stoppers on the Ultra, waste of money in my case..
My take on the "issue" is that its just the nature of the beast.. In fact, I don't even call it blow by.. Think about it, you have a single fork with two pistons going up and down at the same time. When they go up, they create a low pressure in the bottom end. When they come down, they create a high pressure.. At lower rpm's, the breather valve and system work just fine.. But, when you get the r's up, it just becomes overwhelmed and begins to breath a little more than it can contain.. I've done leakdown tests, compression tests, and about everything else I can rationalize.. If you have trouble believing it, try cranking the engine over with the timing plug out of the crankcase.. Hint, don't look in the hole.........
I don't know if that's your issue, but it sure sounds like what I've learned to ignore.. With my breathers set up like I have them, the only time I notice any oil is on startup, sometimes.. When I first start the bike, it may blow a lougie on the ground.. Other than that, I just make sure its not aimed at the tire and keep an eye on the oil level.. Side of the bike stays nice and clean..
I notice it after running the interstate, about 3400(80mph) usually about an hour.. I've installed a Kuryakyn breather with a top/center outlet, allowing gravity to assist as much as possible.. I also run a hose from there, up the backbone and down the front frame legs to vent.. I also tried the slobber stoppers on the Ultra, waste of money in my case..
My take on the "issue" is that its just the nature of the beast.. In fact, I don't even call it blow by.. Think about it, you have a single fork with two pistons going up and down at the same time. When they go up, they create a low pressure in the bottom end. When they come down, they create a high pressure.. At lower rpm's, the breather valve and system work just fine.. But, when you get the r's up, it just becomes overwhelmed and begins to breath a little more than it can contain.. I've done leakdown tests, compression tests, and about everything else I can rationalize.. If you have trouble believing it, try cranking the engine over with the timing plug out of the crankcase.. Hint, don't look in the hole.........
I don't know if that's your issue, but it sure sounds like what I've learned to ignore.. With my breathers set up like I have them, the only time I notice any oil is on startup, sometimes.. When I first start the bike, it may blow a lougie on the ground.. Other than that, I just make sure its not aimed at the tire and keep an eye on the oil level.. Side of the bike stays nice and clean..
Last edited by HGM; Aug 19, 2014 at 09:11 PM.
Seasoned HDF Member
Joined: Nov 2006
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From: la la land jerzey
sometimes the fix for a normal engine with some what low miles that is doing this is an S&S reed breather valve instead of the stock turning type
the reed has a better evac than the turning one - i have installed it every time excess crankcase pressure is present
if its the piston rings or the cylinder walls scored than all bets are off about the breather
the reed has a better evac than the turning one - i have installed it every time excess crankcase pressure is present
if its the piston rings or the cylinder walls scored than all bets are off about the breather
Road Warrior
Joined: Apr 2007
Posts: 1,952
Likes: 15
From: Senoia, Ga., by way of Miami, Fl..
sometimes the fix for a normal engine with some what low miles that is doing this is an S&S reed breather valve instead of the stock turning type
the reed has a better evac than the turning one - i have installed it every time excess crankcase pressure is present
if its the piston rings or the cylinder walls scored than all bets are off about the breather
the reed has a better evac than the turning one - i have installed it every time excess crankcase pressure is present
if its the piston rings or the cylinder walls scored than all bets are off about the breather
Oh yea, got one in both of mine.. I buy into this theory as well..
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Tourer
Joined: Jun 2012
Posts: 417
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From: Maryland
I did forget to say I have the Doherty Machine original power vents installed now that wasn't on the bike when it first started blowing oil. I thought reinstalling the power vents would help some and they have a little. I did use the newest HD white silicone gaskets last time and also replaced the middle rocker spacer on each cylinder as they were warped. I also think some blow by is "normal" but what I had wasn't. I also purchased those Kuryakyn breather top/center outlet but didn't install them but think the power vents are a better choice. What I did last night was to run the clear hoses off of the power vents to a tee that I stuffed part of a sponge thru to help stop or remove the oil from the air and then ran another hose off that tee to the small filter that I mounted by the horn and I also put more sponge in the hose just before the filter. Riding to work today it all seemed to help the blow by. The sponges seemed to work good but will try a longer ride maybe this weekend.
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