100% Biker & Trike Magazine Forums

Go Back   100% Biker & Trike Magazine Forums > 100% Biker > Biker Chat

Notices

Reply
 
Thread Tools Display Modes
  #1  
Old 20-03-2011, 05:22 PM
Billy Balthorpe Billy Balthorpe is offline
Chatter Box
 
Join Date: Jun 2005
Location: In a rusty Capri on bricks in the midlands
Posts: 220
Default Air cooled Honda DOHC woes

My CB 750 Nighthawk which i was going to use for a base for a Bobber is blowing smoke and has low compression on all cylinders, i was hoping against hope that it was the valves slightly propped but no, a squirt of some oil down the bore and the compression shot up to over 200 psi. Conclusion, bores are knackered. Its a shame coz the engine runs very sweet with no rattles, clunks or tapping. I've priced up the replacement pistons for a rebore from David silver and gave up when the total got above 500 for parts alone. So im thinking of putting a CBX750 motor in it. Has anyone had any experience of this or could anyone point me in the direction of a Honda forum which would give me some advice??

Anyway i'm off to put my head in the gas oven, i'm gutted, i MOT'd the thing a week ago as well!
__________________
Team Rejects MCC. Sucesfully taking the piss since 1996.
Reply With Quote
  #2  
Old 20-03-2011, 06:35 PM
mick2's Avatar
mick2 mick2 is offline
Type like a Twat Me...
 
Join Date: Oct 2007
Location: carnoustie, scotland
Posts: 822
Default

do wiseco or similar not do a kit?
i went that route with my gsx1100 because the oversize genuine suzuki pistons were way too much
Reply With Quote
  #3  
Old 20-03-2011, 08:41 PM
Billy Balthorpe Billy Balthorpe is offline
Chatter Box
 
Join Date: Jun 2005
Location: In a rusty Capri on bricks in the midlands
Posts: 220
Default

Quote:
Originally Posted by mick2 View Post
do wiseco or similar not do a kit?
i went that route with my gsx1100 because the oversize genuine suzuki pistons were way too much
I doubt if they would do a kit for my Nighthawk, they would probably do one for the CBX750, but that has a different compression ratio. As they probably use the same heads they probably have messed about with the Gudgeon Pin to piston crown sizes. As i dont fancy finding out it wont work after ive paid for the kit i think ill give it a miss and try to fit a complete CBX750 engine and loom/CDI.
__________________
Team Rejects MCC. Sucesfully taking the piss since 1996.
Reply With Quote
  #4  
Old 20-03-2011, 09:21 PM
John Hopkins's Avatar
John Hopkins John Hopkins is offline
Super Moderator
 
Join Date: May 2006
Location: Tredegar, South Wales
Posts: 16,062
Default

I think I can help..

A flip lid bin bag should fit nicely over your head, tie it round your neck with a scarf and you can do it in the comfort of your armchair.

hope that helps..

John.
__________________
Beauty is skin deep; ugly goes right to the bone
Reply With Quote
  #5  
Old 20-03-2011, 09:56 PM
Billy Balthorpe Billy Balthorpe is offline
Chatter Box
 
Join Date: Jun 2005
Location: In a rusty Capri on bricks in the midlands
Posts: 220
Default

Thanks John, Just the bike to sort out now then!
__________________
Team Rejects MCC. Sucesfully taking the piss since 1996.
Reply With Quote
  #6  
Old 20-03-2011, 11:20 PM
hacky hacky is offline
Self opinionated twat
 
Join Date: Apr 2004
Location: devon
Posts: 2,252
Send a message via Yahoo to hacky
Default

you mention new pistons..why? a rebore and oversize rings would be far cheaper...
__________________
Reply With Quote
  #7  
Old 20-03-2011, 07:09 PM
Fungus's Avatar
Fungus Fungus is offline
Chat Pimp
 
Join Date: Sep 2010
Location: Nr Dover
Posts: 151
Default

Quote:
Originally Posted by Billy Balthorpe View Post
Anyway i'm off to put my head in the gas oven, i'm gutted, i MOT'd the thing a week ago as well!
Not much point in that these days. We use natural gas now which is only lethal after its burnt! You'de roast yer face off before you keeled over from the fumes!

Fungus the Gas (Safe) man
__________________
LIVE NOW PAY LATER!
Can't wait for the weekend. I mean, come on, after Monday and Tuesday, even the calendar says W T F!
Reply With Quote
  #8  
Old 20-03-2011, 08:34 PM
Billy Balthorpe Billy Balthorpe is offline
Chatter Box
 
Join Date: Jun 2005
Location: In a rusty Capri on bricks in the midlands
Posts: 220
Default

Quote:
Originally Posted by Fungus View Post
Not much point in that these days. We use natural gas now which is only lethal after its burnt! You'de roast yer face off before you keeled over from the fumes!

Fungus the Gas (Safe) man
I was waiting for some sad person to point that out.

But i had cunningly sorted a seal from around the open door of the oven over my head and around my neck, so, although i wouldnt die from Town Gas poisoning, i would however die from asphyxiation. Well, i would have done, but i realised that we now have a lovely Smeg dual fuel cooker which replaced the all gas jobby we had before, i actually realised this just after my hair set on fire.
__________________
Team Rejects MCC. Sucesfully taking the piss since 1996.
Reply With Quote
  #9  
Old 21-03-2011, 02:17 AM
Creature's Avatar
Creature Creature is offline
Talk, Type, Breath, Talk, Type, Breath....
 
Join Date: Jun 2004
Location: In a rally field :)
Posts: 7,073
Send a message via MSN to Creature
Default

here ya go - get them to mark it as birthday present

http://cgi.ebay.com/ebaymotors/Honda...Q5fAccessories

also found this

http://cgi.ebay.co.uk/CB750-DOHC-Com...item33662c1987

set of exhaust caskets of ebay around 6.00

So with postage should be back on the road for 300.00 or so !
__________________
...I've been down many a road in my lifetime, but the one I am on now suits me best...at least for the present!
Reply With Quote
  #10  
Old 21-03-2011, 08:22 AM
mick2's Avatar
mick2 mick2 is offline
Type like a Twat Me...
 
Join Date: Oct 2007
Location: carnoustie, scotland
Posts: 822
Default

you cant rebore and use standard pistons so forget that idea.
there is a proper tolerance for piston clearance.
Reply With Quote
  #11  
Old 21-03-2011, 03:15 PM
Billy Balthorpe Billy Balthorpe is offline
Chatter Box
 
Join Date: Jun 2005
Location: In a rusty Capri on bricks in the midlands
Posts: 220
Default

Quote:
Originally Posted by Creature View Post
here ya go - get them to mark it as birthday present

http://cgi.ebay.com/ebaymotors/Honda...Q5fAccessories

also found this

http://cgi.ebay.co.uk/CB750-DOHC-Com...item33662c1987

set of exhaust caskets of ebay around 6.00

So with postage should be back on the road for 300.00 or so !
Yeah, ive seen the first one, i dont want to go and buy it if im going to get problems with the new pistons having a different pin to crown distance as mine has a lower compression ratio than a standard DOHC. Also it may have different pin sizes than mine, its a lot of money for a risk dont you think?

The second one looks good tho.
__________________
Team Rejects MCC. Sucesfully taking the piss since 1996.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 01:02 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.