honda305 Home honda305 Auctions honda305 Gallery honda305 Forum


honda305.com Forum

Login
□ Search
□ FAQ 
□ 
Vintage Honda Owners,
Restorers, Riders and
Admirers

RIght side smoking??

pete lloyd
honda305.com Member
Posts: 8
Joined: Sun Aug 23, 2009 9:30 am
Location: coventry england

right side smoking

Post by pete lloyd » Sun Sep 27, 2009 6:43 pm

First place i looked was valve guide size . Machined a go/no go plug gauge to factory sizes and the bores in the head are spot on sized the valves and they are the same . Checked the rings they are fine and the bores are spot on . I've lapped the valve seats and new gaskets are in the post . Its just with all the bikes i've rebuilt i've never had anything like this .

I have 2 Ariel square fours , 3 Scotts , a Silk , Douglas Dragonfly (now half rebuilt) , a Triumph T120

and a Velocette 250 Mov

But this is my first Honda

e3steve
h305 Moderator
Posts: 2601
Joined: Fri Oct 31, 2003 1:38 pm
Location: Mallorca, Spain & Warsash, UK

Post by e3steve » Mon Sep 28, 2009 4:55 am

Pete, of all those classics that you own, the Honda is the one I'd least expect to be smokey! I'd be inclined to follow G's idea of the problem lying with the O-rings within the corners of the head gasket; the only shortcoming in such a suggestion is that the gasket usually bursts outward, thus creating a visible leak. Now, I'm no mechanical expert, but I guess it's possible for the gasket to fail in any direction. Follow this topic http://www.honda305.com/forums/viewtopic.php?t=4520 for more detailed info and make up your own mind; you'd think any failure would progress in the weakest area.

Probably a dumb Q, but have you closely, I mean, microscopically, inspected the head / barrel faces for signs of hairline cracks or other imperfections that would allow oil to seep on one side? A compression test should reveal something along those lines.

The valve guides would need to be noticeably worn to make the motor a smokey-Joe.

User avatar
G-Man
honda305.com Member
Posts: 5678
Joined: Wed Mar 25, 2009 5:17 pm
Location: Derby, UK
Contact:

Post by G-Man » Mon Sep 28, 2009 6:58 am

Pete

Just 'remembered' a potential problem with these engines. That is the cast iron 'skull' losing adhesion in the aluminium head, allowing oil seepage (usually out via the spark plug threads. A distant possibility but if you search this forum you might just find something. Or did I dream it?.........

I wouldl take Steve's route initially and look for hairline cracks or marks in the joint face.

Regards

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

e3steve
h305 Moderator
Posts: 2601
Joined: Fri Oct 31, 2003 1:38 pm
Location: Mallorca, Spain & Warsash, UK

Post by e3steve » Mon Sep 28, 2009 7:11 am

I, too, forgot about the skulls! But, I should add, I've never read -- in Bill's books or on the forum -- about skull separation causing a smokey exhaust; just about the oil leaks around the spark plugs.

Good call, though!

pete lloyd
honda305.com Member
Posts: 8
Joined: Sun Aug 23, 2009 9:30 am
Location: coventry england

right side smoking

Post by pete lloyd » Mon Sep 28, 2009 5:50 pm

Going to have another look at the state of the gaskets and seals as i can't think its anything else . The new gaskets should be here in a couple of days so before they get here i'm going to lap the head and barrel together so they are dead flat. Good idea about getting the head crack tested . I'm lucky enough to have that at work so its going to x-ray , NDT and UV dye .

Just forgot its only done 15,500 from new if thats any help .

User avatar
G-Man
honda305.com Member
Posts: 5678
Joined: Wed Mar 25, 2009 5:17 pm
Location: Derby, UK
Contact:

Post by G-Man » Tue Sep 29, 2009 12:46 am

Pete

Just one or two more trivial thoughts.

Rings in the right way up?
Ring gaps spaced nicely around the piston?
Valve guides loose in head?
Residual oil in exhaust? - I sometime squirt oil in my silencers to 'preserve' them.

I realise these are a bit desperate but when you've checked everything it's going to be something daft.....

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

pete lloyd
honda305.com Member
Posts: 8
Joined: Sun Aug 23, 2009 9:30 am
Location: coventry england

right side smoking

Post by pete lloyd » Tue Sep 29, 2009 4:11 pm

Get the head back tomorrow from crack test so we will see if there anything there . If not it just going to be a bloody good clean and a vey careful rebuild when the gaskets come.Trust the post to go strike just when i need something !

Post Reply




 

CB-77 | CYP-77 | Road Test | Riding Log | Literature | Zen | Marketplace | VJ Survey | Links | Home