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Oil from breather pipe

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Geoff Hastings
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Joined: Wed Feb 22, 2017 2:59 pm
Location: Epsom, Surrey

Oil from breather pipe

Post by Geoff Hastings » Wed May 24, 2017 7:32 am

Hi there,
I've just fired up my CA77 for the first time. The bike was bought at an auto jumble and I did strip the engine and examine it. Despite the speedo reading 14,000 it was on 1mm oversize Pistons so has done quite a few miles. The bores were OK, you could still see the honing marks and ring gaps were correct so they were left. I just changed the cam chain and reassembled the engine, after a short run there was a fair amount of oily vapour dripping out the cylinder head breather pipe. I'm kind of hoping that it's not excessive blow by causing this, can anyone advise please.

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G-Man
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Post by G-Man » Wed May 24, 2017 3:43 pm

One thing to check is that you assembled the plate on top of the head the right way around as it forms a labyrinth to separate oil from any air being pumped out.

https://www.cmsnl.com/honda-cl72-scramb ... SXwOcm1vpg

Did you hone the bore at all to break up any glaze?

New rings or old?

Fit of valves in guides?


G
'60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160
'66 Matchless 350 '67 CL77
'67 S90 '77 CB400F

Geoff Hastings
honda305.com Member
Posts: 363
Joined: Wed Feb 22, 2017 2:59 pm
Location: Epsom, Surrey

Post by Geoff Hastings » Wed May 24, 2017 4:16 pm

G-Man wrote:One thing to check is that you assembled the plate on top of the head the right way around as it forms a labyrinth to separate oil from any air being pumped out.

https://www.cmsnl.com/honda-cl72-scramb ... SXwOcm1vpg

Did you hone the bore at all to break up any glaze?

New rings or old?

Fit of valves in guides?

The bores were not glazed, honing marks still visible, I did reuse the rings as the gaps were within limits. Valves were OK in their guides but I was a bit puzzled by the lack of stem seals. I must admit that I reassembled the plate the way it came out but that's not say it was put together properly the last time. I did find a crack in the cases as they had not aligned the main bearing pins with the holes correctly and then tightened the case bolts. Looks like I'll have to pull the top end apart again.
G

Nick
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Post by Nick » Wed May 24, 2017 11:56 pm

If the breather effluent is being caused by blow-by from the rings not seating, you may as well run the bike for a while to see if they bed in. Put a little catch bottle at the end of the breather tube and see how much is actually being spit out - a little mist is nothing to worry about.

Didn't over-fill the crankcase with oil by any chance?

Valve guide seals not needed.
Do what you've always done and you'll get what you've always had.

Geoff Hastings
honda305.com Member
Posts: 363
Joined: Wed Feb 22, 2017 2:59 pm
Location: Epsom, Surrey

Post by Geoff Hastings » Thu May 25, 2017 2:52 am

Nick wrote:If the breather effluent is being caused by blow-by from the rings not seating, you may as well run the bike for a while to see if they bed in. Put a little catch bottle at the end of the breather tube and see how much is actually being spit out - a little mist is nothing to worry about.

Didn't over-fill the crankcase with oil by any chance?

Valve guide seals not needed.
Thanks Nick and G man, I'll probably run it as suggested with a catch bottle for a few days. There was no smoke in the exhaust and I did only run it for about 10 minutes.
I found another problem at start up, the fuel tap bowl had a pin hole in it and this leaked fuel all over the freshly painted engine, which I then found out was not fuel resistant so most of the paint ended up on the drive. Oh well.

Geoff Hastings
honda305.com Member
Posts: 363
Joined: Wed Feb 22, 2017 2:59 pm
Location: Epsom, Surrey

Oil from breather pipe

Post by Geoff Hastings » Wed Jun 07, 2017 6:30 am

G-Man wrote:One thing to check is that you assembled the plate on top of the head the right way around as it forms a labyrinth to separate oil from any air being pumped out.

https://www.cmsnl.com/honda-cl72-scramb ... SXwOcm1vpg

Did you hone the bore at all to break up any glaze?

New rings or old?

Fit of valves in guides?

Hi G-Man. As I have a bit of time before I can get the bike uk registered I decided to pull the top plate off the engine and check whether I had put the baffle plate on the right way round as suggested. There was no baffle plate fitted! I did wonder at the time why the gasket kit had two gaskets and looking at an exploded view it's obvious but I re-built the engine as I found it without a manual. Strange why someone would leave out part of the engine, it's not as if it wears out. Anyway, I've ordered a new one. Thanks for the info.


G

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