Norton Motorcycle Tech Talk

Home

Printer-friendly copy
Online Resources
Norton Manuals / Dyno Dave / MotoCycles.com / Daytona Bike Week
Top Norton Motorcycle Tech Talk Forum Topic #491   Previous topic | Next topic   
Ian WilsonFri Feb-25-05 04:45 AM

  
"Breather valves solve oil leaks?"


  

          

Hello everybody.

I've come across an INOA article of a few years ago that talks of a brake booster valve being used in the breather line of a Commando to stop oil leaks.

Apparently, the theory is that at 4500 rpm there is +2psi oil pressure in the engine, in standard form, which in turn forces oil to the outside of the engine through the weakest points.

This breather valve is put in the 'big breather pipe' (?) and allows a negative crankcase pressure and effectively keeps the oil sucked in. Great things are claimed. Like a reduction of 300 miles/qt to 700 miles/qt.

The brake breather valve comes from Colorado Norton Works and is Motormite/HELP #80190 Brake booster valve.

Anybody used it? Anybody got any constructive comments on this or any other device/method to keep oil inside the engine?

Got to say that if the Commando engine (mine is a Mk3) has indeed got positive pressure in it at speed then it is no surprise that they allow oil out! If this is the case, then the problem, and a cure, must be well known.

Anybody able to throw some light on this? Does it work? Where is it fitted then?

Thanks in advance,

Ian Wilson

  

Alert Printer-friendly copy | Reply | Reply with quote | Top
zotzFri Feb-25-05 05:01 AM
Member since Mar 18th 2009
9 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#1. "RE: Breather valves solve oil leaks?"
In response to Reply # 0
Fri Feb-25-05 05:03 AM by zotz

  

          

I can't say for sure about the reduction of oil consumption but as far as leaks are concerned yes it does work. I struggled for the longest time with oil weeping from between the head and barrel at the push rod tunnel. Even after re-torquing it would still come back after a while. I didn't want to pull the head so I put up with it. After installing the valve the problem disappeared for good. I mentioned the fix to my friend who was having the same problem and it worked for him to. You can get the valve from a regular automotive parts supplier.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

BrithitSat Feb-26-05 07:30 AM
Member since Mar 18th 2009
149 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#2. "RE: Breather valves solve oil leaks?"
In response to Reply # 0


  

          

Ian,

I would second that. I use the Motormite booster valve on both my MKIII and '72. The Combat has the breather mod as shown in the Tech Digest. The valve is "L" shaped. I think the right-angle turn of it actually helps installation, at least in my case. The big end of the valve fastens to the breather hose, then makes a right angle, and you use a shorter piece of smaller hose to connect to the oil tank. Hard to describe, but once you have it in your hand, it will make sense. As far as decreasing any oil leaks, I can't say for sure in my case, but I have very little, if any, of the kind of seepage problems this fix will address. Both of my engines have been rebuilt from the crank-up, so I'm not expecting much leakage, especially with fresh top-ends. My son (the machinist) just did the tach drive seal mod for me on both bikes. That seems to be the biggest culprit of leaks in my case. Another sore spot for me on the Combat is getting a good seal on the rocker feed banjos. Think I need to take those off and face the round part of the banjos. Even with a fresh copper gasket, they like to dribble a little. I do think this is worthwhile on your end to try the booster valve. Very cheap project!

Don W.

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

andersonSun Feb-27-05 10:14 PM

  
#3. "RE: Breather valves solve oil leaks?"
In response to Reply # 2


  

          

Hi
For the benefit of those outside the US, and therefore unable to sight one at a local supplier, could someone please describe the action of these valves.

I use a one way breather flapper valve from a 1980s BMW Boxer breather system on my Dommie. I imagine this does the same thing but would like to know for sure.

John

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

dynodaveyMon Feb-28-05 07:16 AM

  
#4. "RE: Breather valves solve oil leaks?"
In response to Reply # 3


  

          

Hi John
Done any racing this season?
The first technical points of this valve is that it is a check valve with a very low "cracking pressure".
The second point is that these have a very low mass to the valve device for quick response time. A high mass ball bearing in a pcv valve will not respond fast enough....

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

andersonMon Feb-28-05 05:57 PM

  
#5. "RE: Breather valves solve oil leaks?"
In response to Reply # 4


  

          

Hi Dave,

Good to hear from you. From your description the BMW breather valve will do the same thing. It is a one way valve with a piece of light weight spring steel as a flapper. I imagine it would vibrate at high frequency and has low mass.

On the racing side. Im still limping a bit from my off a year ago but more frustratingly I have found I bent a lot of things but just a little so it is hard to spot. Frame, front forks, yokes, front axle !!

Im having a really difficult time getting the front supension working well. I have had it apart maybe five times now. Stantions are perfectly parallel in both planes, I rebored the axle holes perfectly square to the sliders, the slider is faced off square to the brake plate, the axle is straight, each slider moves perfectly on the stantion, dummied up with no dampers or springs the wheel moves perfectly on the forks with no stiction - but put the whole lot together and the suspension is almost solid. Every measurement seems to be perfect but together it binds up. Next step is to make a dummy spacer to put in instead of the wheel and reassemble step by step to find the cause.

To make matters worse my Commando front end is perfect and I just threw it together. Perhaps Im trying too hard and I should "British engineer" in a few sloppy clearances !

John

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

750roadsterTue May-27-08 05:40 PM
Member since Mar 18th 2009
1 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#6. "RE: Breather valves solve oil leaks?"
In response to Reply # 0


  

          

Tis true! I use them and swear by them. I put my first on one a 71 Combat Commando that was WORN OUT (read heavy blow-by, excessive positive crankcase pressure)-leaking oil from everywhere. I cleaned the bike with Gunk after putting the valve on and the motor was leaking almost NO oil after 1,000 miles. When the Combat finally bit the dust, I put one on my new 850 motor and after 3,000 miles, the underside is dry as a bone.

The one they recommended is smaller than the one I used-go to a NAPA or other parts store on a slow day and get them to look up a model with 3/4" inlet/outlet....

Good Luck

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

seaguySun Sep-06-09 09:45 AM
Member since Jun 23rd 2009
2 posts
Click to send private message to this authorClick to view this author's profileClick to add this author to your buddy list
#7. "RE: Breather valves solve oil leaks?"
In response to Reply # 6


          

>Tis true! I use them and swear by them. I put my first on
>one a 71 Combat Commando that was WORN OUT (read heavy
>blow-by, excessive positive crankcase pressure)-leaking oil
>from everywhere. I cleaned the bike with Gunk after putting
>the valve on and the motor was leaking almost NO oil after
>1,000 miles. When the Combat finally bit the dust, I put one
>on my new 850 motor and after 3,000 miles, the underside is
>dry as a bone.
>
>The one they recommended is smaller than the one I used-go to
>a NAPA or other parts store on a slow day and get them to look
>up a model with 3/4" inlet/outlet....
>
>Good Luck
750roadster if you are still around I would like to know where you installed the breather on your 71 commando engine. I am in the middle of a rebuild on a 71 engine and am trying to find where the best place to install an xs650 reed valve mod. It would be nice to do what needs to be done to the case while it is apart and on the bench. Everything I read about is 72 and newer.
regards, Rich

  

Alert Printer-friendly copy | Reply | Reply with quote | Top

Top Norton Motorcycle Tech Talk Forum Topic #491 Previous topic | Next topic





Norton Commando Oil Change