Honda Twins banner
1 - 5 of 5 Posts

·
Registered
Joined
·
4,402 Posts
Discussion Starter · #1 · (Edited)
I'm working on a 1979' CM185T Twinstar and have found that the breather/separator is restricting the PCV system from allowing a free flow of crankcase output to be sucked-through back into the engine through the airfilter as Honda has designed it;I have found this problem to be caused by the small foam breather filter getting completely clogged-up and not allowing vapor to escape into the air filter.This has caused pressure to build-up inside the crankcase and causes the bike to burn oil by pushing oil past the piston rings to a degree.I'm glad it hasn't blown any oil seals yet.. I have already done a bore job w/ fresh pistons and rings and the new rings haven't seated plus the cylinder walls have a burned-on oil film because of the oil pushing past them constantly from crankcase pressure.
I have removed the small foam filter disc from the breather/separator below the air filter box which has seemed to help the restriction although it may not be quite restrictive enough and possibly allow more oil vapor to be sucked into the engine. I want to finally get this engine to be tight and keep it from using oil this way.
Have any of you done other modifications to the existing early design oem breather/separator assembly below the air box to keep it from building-up crankcase pressure ? I would rather not remove the oem breather/separator as it's required equipment here in CA. I could let it push oil vapor out the back from an open hose but that can let oil onto the back tire causing a slippery situation plus an accident.
 

·
Registered
Joined
·
4,402 Posts
Discussion Starter · #3 · (Edited)
I want to see what can be done to set-up the stock breather/separator to leave it installed and make it work the best it can without building up pressure inside the crankcases because of the little foam filter inside getting plugged-up.Has anyone here installed a screen mesh in place of the oem Honda foam filter inside the breather ? The type/style of the breather I'm speaking about is part# 17361-419-670 which is the main body of it.
 

·
Registered
Joined
·
9,796 Posts
  • Like
Reactions: bilbikek411

·
Registered
Joined
·
4,402 Posts
Discussion Starter · #5 · (Edited)
In the late 70 and early 80's Ford small blocks, they used a crankcase vent filter that used a fiber rather than foam. Using the fiber material from one may work. https://www.carid.com/1980-ford-f-1...breather-filter-736516234.html?parentsubmodel[]=ENGINE|4.9L
Thanks Dan,I'm going to consider that as the fiber may be less restrictive.
I think that running the breather w/o any filter as I am now may cause the air filter to suck more vapor/oil and possibly use oil which could cause a problem if he didn't carry extra oil on a long ride someday.
I wonder if any other members here have had issues with that type of breather and if installing a fine mesh screen of sorts could help ? I have worked on other Honda's(singles like the XL185 enduro,etc.)that use that same round breather/separator under the airbox held on with 3 small screws.The XL185 was used for commuting on the street.I removed the round foam filter material from them and they did ok., I told the owner to keep an eye on the oil level regularly and so far I think it has worked for them.I would like a more sure 'fix' that will work out for both a 'breather' and 'separator'.
 
1 - 5 of 5 Posts
Top