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Discussion Starter · #1 ·
I have the cases split on my '71 right now and I'm thinking of doing the front breather mod. I've researched around an found some info about it. From what I understand you drill holes in the top and bottom of the front triangle/Motor mount. Fill the area with plastic mesh. Then tap a fitting through the case. I was wondering if I have to run a PVC valve or can I just run it under to dump out? I'm running 66 frame, so, I can't just run it to the frame and I don't want tubes all over my bike. The whole reason I want to do this is to separate the oils.
 

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I've never heard of that, guess I'll do a search cuz it sounds interesting.

I used the stock breather but added a PCV valve to try inducing negative pressure in the crankcase. I think it worked as I had very little leakage.
 

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Tat,I did this 20 years ago on my Hot Rod Triumph and it can work great. A few tips. First, since your crank is spinning and throwing oil,drill the holes at a 45 degree angle down so you avoid as much oil in the cavity as possible.Two, I drilled about (10) 1/8 th inch holes in each side of crankcase(at 45 degree angle), and (2) 1/4 inch holes in the bottom corner corners of the cavity to drain any oil that may accumulate. Three, run a one-way valve, I run a spyke krankvent,but I have since used Mike's XS one way vent/valve with good results on other motors. In case you don't know,this is an old flat track motor trick. Jack
 

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we do the front vent all the time when doing a belt drive on a T140, we use a PCV valve and then run the vent tube right up to the OIF tank and braze a 3/8" tube into the oil tank and point the tube towards the back of the bike. there is a factory vent right near the neck that will vent the engine just fine.
 

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With the OIF frame, I've found that under hard braking, oil will slosh to the front of the top tube, and exit the breather for the tank. I put a T in the line from the crankcase breather that you and Jack are refering to so any oil that comes out of the frame will drain back to the crankcase. Install your krankvent to the atmosphere side of the arrangement so it won't prevent the oil from draining back to the crankcase.
 

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Discussion Starter · #10 ·
I drilled the holes. I'm getting ready to tap for the fitting. I was wondering about the valve. Tony are you using a regular automotive pcv valve? I like that it's in line.
 

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yes I use the regular old automotive type PCV's on the front mount type, never had any trouble with the auto type as long as they are mounted vertical. and I've used the Yamaha reed style too. the reed style is a better valve but they are huge and ugly,
Map Cycle has a $50 kit with a reed valve, it works pretty well for a timing plug breather, don't try the timing plug breather without one it makes a holy mess out of things.
 

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Discussion Starter · #12 ·
I plan on running it down under the motor and venting it into the air. Do you think I even need a valve? The hose would probably be 2 feet long so I don't know any contaminates would make it that far. Ifit would be better I can just pick up a reed valve.
 

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a vent line going down will work but the whole thing with a PCV valve is all about keeping the crank case in a vacuum and all the benefits it brings, like no leaks.
 

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Tony, I found this old thread and I am currently fitting a belt primary drive and I will need to run a crankcase breather. If I have a pre OIF model where would I run the breather tube to? Could I just fit a K&N type right on the PCV valve?

Thanks, Dan.

Edit:

As I am not planning on dismantling the engine I cannot run a breather from the front triangle as you example above. I see that people have run a breather from the timing port at the back of the cylinder block. Any thoughts on this?
 

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Tony, I found this old thread and I am currently fitting a belt primary drive and I will need to run a crankcase breather. If I have a pre OIF model where would I run the breather tube to? Could I just fit a K&N type right on the PCV valve?

Thanks, Dan.

Edit:

As I am not planning on dismantling the engine I cannot run a breather from the front triangle as you example above. I see that people have run a breather from the timing port at the back of the cylinder block. Any thoughts on this?
this was covered above , if you vent from the timing hole you MUST use a PCV and it is advisable to run a catch can !!
 

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pre oil in frame maybe not needed
problem is 71(and other years?) bikes that vented into primary.
 

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Thanks RichBob, mine is a '71 and does breath into the primary, I can run into a catch can and use a pcv. I will have to plug the breather holes.

Is this, using the timing port the best option, I mean can I maybe breath from the tacho port or the oil pressure port on the timing cover? Just a thought. Don't shoot me.

Gearhead, I am sorry if I missed something on this thread, I'm dyslexic so I don't read too well.
 

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yea your on right track
bunn breather
guy, got in uk just got to check invoices .
 

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yea your on right track
bunn breather
guy, got in uk just got to check invoices .
Yes, the Bunn breather system is fine, I've installed several and it's a good kit.

you need to block off the 3 little oil level holes .... ( I use the same 3 little rivets that hold the Triumph patent plate on )

...and.... put a crankshaft seal around the belt drive pulley , ( the 1970 and up motors don't have that seal ).
 
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