Crankcase Vent Pressure
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Seasoned HDF Member
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From: Lake, Ms
Crankcase Vent Pressure
Is there any way to check the crankcase breather on a twin cam to see if they are clogged and not venting properly? I'm still trying to determine why I'm getting Blue Smoke from my rear cylinder exhaust. It only does this after the bike is hot and an extended idle. Once on the throttle there is one good puff of smoke and it's gone until I stop again. Compression tests were good at 190 and 195. Leak down tests were good also with only 9% leak down in both cylinders. Bike used almost a quart of oil on a recent 700 mile round trip to Baton Rouge. Was in a lot of stop n go traffic as well. Dealer keeps insisting that my tune is causing the smoke but I'm not buying that. I'm running a custom map on my PV from Dragos Bike Works and the bike runs and performs flawlessly other than this. For what it's worth, the bike will still smoke with the stock tune and a/c on as well. Any thoughts or input cause I surely need all the help I can get.
2010 Limited with some stuff
2010 Limited with some stuff
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
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From: Phoenix '53, '88, '09 Big Twins
oil is more white smoke.
smoke on accel is worn piston rings/ bad piston to cylinder seal
smoke on decel is worn valve seals ( the high motor vacuum when the throttle is closed will suck oil past bad seals- these valve seals are protected from the combustion by the valves when closed)
just pulling your dipstick would relieve any pressure in the crankcase if you think the system is over pressured- try testing with dipstick pulled.
but oil burning makes white smoke, not black or blue
black smoke is unburned gasoline
mike
smoke on accel is worn piston rings/ bad piston to cylinder seal
smoke on decel is worn valve seals ( the high motor vacuum when the throttle is closed will suck oil past bad seals- these valve seals are protected from the combustion by the valves when closed)
just pulling your dipstick would relieve any pressure in the crankcase if you think the system is over pressured- try testing with dipstick pulled.
but oil burning makes white smoke, not black or blue
black smoke is unburned gasoline
mike
Last edited by mkguitar; Aug 1, 2014 at 11:52 AM.
Extreme HDF Member
Joined: Sep 2010
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From: Phoenix '53, '88, '09 Big Twins
using any additives like "seafoam" ?
some additives do not burn completely ( see my post on seafoam and failing emissions testing...) and could make the "black smoke" of a rich mixture appear more blue/white
lost oil- it's not showing up in the primary is it?
Mike
some additives do not burn completely ( see my post on seafoam and failing emissions testing...) and could make the "black smoke" of a rich mixture appear more blue/white
lost oil- it's not showing up in the primary is it?
Mike
Last edited by mkguitar; Aug 1, 2014 at 12:04 PM.
Thread Starter
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Seasoned HDF Member
Joined: Jan 2013
Posts: 10,637
Likes: 1,246
From: Lake, Ms
2010 Limited with some stuff
Thread Starter
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Seasoned HDF Member
Joined: Jan 2013
Posts: 10,637
Likes: 1,246
From: Lake, Ms
Trending Topics
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
pulling the dipstick will "unseal" the closed system
really unlikely that anything would hinder the valve closing- the valve springs are very strong
mike
really unlikely that anything would hinder the valve closing- the valve springs are very strong
mike
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Thread Starter
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Seasoned HDF Member
Joined: Jan 2013
Posts: 10,637
Likes: 1,246
From: Lake, Ms
2010 Limited with some stuff
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
you got me...
if you were to think that your seals are hardened and not pliable...you could try a auto tranny stop leak additive.
what these do is swell the seals in a tranny to stop leaks, the swollen seals are more pliable.
but like any magic potion the results are temporary. ( and most of these are just rubbing alcohol, so you don't want that displacing oil in the bearings-)
but that might tell you if your umbrella valves are bad- i doubt it though
as far as a stumble or un-even idle- if you have mods- the more mods the more variables.
and are you experiencing a warning of impending doom? or just a new-normal?
you could try just using the sole of your boot to block part of the exhaust outlet while idling, see if that changes anything- if so you could be seeing the results of a harmonic pulse in the exhaust- which will always be very rpm specific and may occur again at 2x and 4x the observed rpm
mike
if you were to think that your seals are hardened and not pliable...you could try a auto tranny stop leak additive.
what these do is swell the seals in a tranny to stop leaks, the swollen seals are more pliable.
but like any magic potion the results are temporary. ( and most of these are just rubbing alcohol, so you don't want that displacing oil in the bearings-)
but that might tell you if your umbrella valves are bad- i doubt it though
as far as a stumble or un-even idle- if you have mods- the more mods the more variables.
and are you experiencing a warning of impending doom? or just a new-normal?
you could try just using the sole of your boot to block part of the exhaust outlet while idling, see if that changes anything- if so you could be seeing the results of a harmonic pulse in the exhaust- which will always be very rpm specific and may occur again at 2x and 4x the observed rpm
mike