P92 Breather

Here we can talk about the P92

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minetymenace
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P92 Breather

Post by minetymenace » Mon Dec 13, 2004 1:46 am

See Thread P92.

The breather is above the final drive sprocket, what are the pro's and con's?

Any ideas? Shielded by the clutch etc.... About to close the bottom end, but if this is any benefit or detriment to moving it to a less obtrousive position, now would be a good time to know....

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Breather

Post by Bill » Mon Dec 13, 2004 2:17 am

Similar position to a 1974 oil in the frame T140 Bonnie, also the TR5T, If I recall right you can remove those breather adapters which are in the same in position, so maybe you could get hold of a bonnie one and adapt it to fit.

T140 one also had a pipe, which connected up to the frame oil tank breather at the headstock. They removed the crankcase seal, which was on earlier bonnies and allowed the chain case oil to self-level

By the way don’t do this to a b25, as it has a crankshaft seal and will not breath the motor.

Bill.

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Post by minetymenace » Mon Dec 13, 2004 3:07 am

Thanks Bill, I'll check out the Bonnie breather, I think it is best to breath into a non-return valve as per HPStans advice on the B50.

The position looks like it is in the way of the clutch though....

Don't they sleep in Scotland, you replied at 01:17 GMT, nearly as sad as me!!!!

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Post by Andrew » Mon Dec 13, 2004 10:47 am

there is room just behind the clutch. the only risk would be breaking a chain and then clouting the breather pipe stub. worst case is that you might crack the chaincase if the broken chain catches on the stub...

mine breathes out the top of the chaincase cover. not quite as neat, but at least its out of harm's way...

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breather

Post by ghislain » Mon Dec 13, 2004 1:07 pm

On mine, did replace the piece of tube by a connecting part from a 750 H*nda (oil), same colour, same diameter, so you can reuse the marvellous grey/green hose, easy to fit to primary chaincase, no leaks (o ring )just drill two fixings on primary...

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Photo

Post by b50root » Mon Dec 13, 2004 2:31 pm

Hi Ghislain. any photo ?

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Post by JB » Mon Dec 13, 2004 7:14 pm

I have owned a 75 T140 and a 75 T160 and both of these had the breather coming out from behind the primary chain rather than above it. Both of these bikes had a sort of labyrinth chamber that acted as a froth tower to seperate the air from the oil and if memory serves me right the T140 piped the collected oil onto inside run of the primary chain.

On a B50 I think fitting the breather behind the chaincase looks better, but I can't see how it can work any better than the original set-up? Probably even worse!!

JB

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Post by minetymenace » Tue Dec 14, 2004 1:56 am

Thankyou all, I like the asthetics of having it hidden but want to keep the breathing sweet. My Beesa triple seems to breath straight into the centre of the air filter with only minor baffles, but with a constant volume crank case on the tripple we are talking chalk and cheese. Anything that inhibits breathing seems to be bad............unless you know otherwise 8)

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Post by JB » Tue Dec 14, 2004 9:42 am

Good point about the triples.

650/750 Bonnie's from a breathing point of view, could be considered as a large crankcased singles, because both its pistons rise and fall as one.

JB

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Post by Mark Cook » Tue Dec 14, 2004 6:00 pm

Been running one for years with no problems, but I would never install a none return valve. Just a good qaulity filter!

Image
Last edited by Mark Cook on Fri Jun 23, 2006 10:09 am, edited 1 time in total.

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Post by minetymenace » Tue Dec 14, 2004 8:35 pm

Thanks Mark, remind me of this when I bring my head round next year!!

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Post by JB » Wed Dec 15, 2004 2:27 pm

I wonder if the P92's breather had an oil seperating chamber? If it had been launched, I would have thought it would have to have the breather fed to the air box to comply with new laws just like the LH gear lever. :roll:

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Post by kommando » Wed Dec 15, 2004 9:44 pm

I fitted a Triumph 90 degree breather union to the back of the crankcase above the Gearbox sprocket by tapping the case for 2 2BA allen screws must have been 8 years ago on a C15 and have done same on 2 B44 crankcases since. Works realy well.

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Post by minetymenace » Thu Dec 16, 2004 5:02 am

JB, was the LH gearchange legislation or marketing (copying the Japs)?

kommando, In the crankcase?! The ideal place for it, but what about the stresses on a tuned B50 engine, and the mist spray and general gasseous nature of anything thrashing aroung the crankshaft at x thousand revs. Where would it breath to? I think you would need a container the size of a minor gulf oil state? At least if you breath through the primary drive there is some still(ish) air for most of the oil to settle out. Do you have a picture of the Trumpet breather?

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Who's moved me gearlever!!

Post by JB » Thu Dec 16, 2004 10:27 am

In America Mr H*#@das advertising campaign that "you meet the nicest people on a H#@%da" had reawakened the declining motorcycle market there in a big way. As a result there where thousands of youngsters in the USA who had learned to ride on small cc bikes with left foot gearlevers.

Virtually all big bikes at the time had right foot change ( Harley, Ducati, Triumph etc.) I guess a lot of accidents must have been blamed on this large group of young riders when they moved up to a bigger bike with its right foot lever. As a result a law in America was passed that meant every road bike had to have a left foot shift which must have come into effect around 75 as all the remaining Brit bikes by then (only three left anyway T140, T160 & Commando) had been changed over to left shifting. The new law would have obviously been known well in advance to allow time to change which is why the 350 Bandit/Fury for 71/72 launch had a left foot shift straight from the drawing board, interestingly to make the 350 left shift they mirrored the whole bottom end so the clutch(B50 clutch!!!)/primary drive was on the right and the final drive also.

So the P92’s gearlever was on the left for a good reason.

JB

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Post by Mark Cook » Thu Dec 16, 2004 11:09 am

Me thinks an accountant must have been in charge of that design!! :?

Sorry to any of you that might be one, all in jest :)

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Post by kommando » Thu Dec 16, 2004 12:01 pm

Sorry did not explain, mine breathes from the Primary too in much the same postion as Mark's but it is a 90 degree elbow on a flange which is retained by 2 allen screws.

Just making up a B40F and I have drilled into the redundant distributor shaft hole on the timing side above the bronze bush from the camshaft chamber, breather will be simply a tube screwed into where the distributor went.

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Crankcase Breather

Post by Canberra » Thu Dec 16, 2004 1:09 pm

As I have just sealed off the primary case I made up a fitting to move the breather to where the tacho drive is fitted as suggested on the forum. I am of the feeling that when the bike stops accelerating then change up (I love that quote from another string) so I was not using it anyway. I will let you know if I manage to fill a small container with oil from it.

The original tube through the top of the primary case leaked like a sieve after a while so I had to manfacture a fitting to suit that sealed it. Another poor original design point that needed attention so I am not surprised the last B50 design changed it.

John

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Post by Mark Cook » Thu Dec 16, 2004 3:20 pm

Just one thing that would worry me, is that by venting the crankcase on the right hand side, is that the cam uses that pressure to cool and lubricate it. Will be interesting to hear if it has any adverse affect with you high milage boys?

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