Crankcase breather outer diameter - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 10 (permalink) Old 11-02-2012, 02:49 AM Thread Starter
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Crankcase breather outer diameter

What outer diameter crankcase breather do I need for the stock crankcase breather hose?

I read through 11 pages of Forchetto's "free horsepower" thread and couldn't find this info.

Thanks!
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post #2 of 10 (permalink) Old 11-02-2012, 01:48 PM Thread Starter
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Any help on this one?
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post #3 of 10 (permalink) Old 11-02-2012, 02:13 PM
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12 - 13 mm
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post #4 of 10 (permalink) Old 11-02-2012, 02:59 PM
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Bonnies up to 2005 or 2006 had 6 mm (around 1/4") outlet breathers, from then on they have 13mm (1/2").
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post #5 of 10 (permalink) Old 11-02-2012, 03:23 PM Thread Starter
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Wow that's a large difference in the I/D of the housing. I wonder if it's worth it to upgrade the hose on my '01 from 6mm to 12mm. I'd imagine that I'd need to use some sort of reducer on the outlet from the crankcase.
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post #6 of 10 (permalink) Old 11-02-2012, 03:38 PM
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1/2" at the end of the stock breather hose.

/M

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post #7 of 10 (permalink) Old 11-02-2012, 03:42 PM
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Bob Farnham tuning in the UK removes the clutch to re-drill the crankcase to accept the newer 13mm (1/2") outlet.

The increase in outlet diameter might not seem much but you have to consider the area, not just the diameter. Doubling the Diameter increases area by four times.

6mm diameter breather pipe area = 28.27mm2

13mm breather area = 132.73mm2

Earlier bikes, up to VIN number 221608, had their breather hose outlet spigot attached to the inner pipe/seal assembly, like this:



Later ones don't have that pipe and the spigot is just a push-in fitting I believe. Not sure how it's held in the crankcase.

Last edited by Forchetto; 11-03-2012 at 07:04 AM.
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post #8 of 10 (permalink) Old 11-03-2012, 12:24 PM
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I use a UNI UP-123 on my 2008 Bonnie, using the original breather hose. It's a 1/2"

Bike Bandit lists the same breather hose for the 2001 as for the 2008. I'm a bit confused the the picture above and the reference to 1/4", so I hope I'm not answering the wrong question.
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post #9 of 10 (permalink) Old 11-03-2012, 02:51 PM
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Quote:
Originally Posted by BonnieBlack View Post
Bike Bandit lists the same breather hose for the 2001 as for the 2008. I'm a bit confused the the picture above and the reference to 1/4", so I hope I'm not answering the wrong question.
There are two different breather hoses listed in World of Triumph:

Up to VIN 221608 plus numbers 229407 to 230164 the breather outlet hose is part number T2201705

Newer engines use hose T2200189


Source:

http://www.worldoftriumph.com/triump...&block_03=3130
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post #10 of 10 (permalink) Old 11-09-2012, 06:01 PM Thread Starter
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Ok so I measure my breather hose inner diameter with a pair of calipers and its .05 inches or about 12mm. So I guess I have a newer breather system on my 2001 bonnie?
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