Honda CG125 smoking exhaust

pb399 · L Plate Warrior Joined: 03 Aug 2004 Karma :

Hi,
Just inherited a 1991 CG125, 16k miles and pretty good condition except the exhaust smokes alot when I rev it.

I've got a Haynes manual which says it could be the valve guides or piston rings - does anyone have any idea of how much it costs to get a new set of piston rings and the cylinder rebored? What the hell are valve guides? Would it be cheaper to try and get an old CG and swap the engine?

Also, how hard would it be to fix myself - I have access to lots of tools and a bit of mechanical experience, but not huge amounts of time. The bike runs ok, but it's a bit anti-social to leave clouds of smoke behind every time I pull off Embarassed

Any tips? Anyone out there fixed a CG before - any help much appreciated Very Happy

mr jamez · World Chat Champion Joined: 04 Aug 2003 Karma :

Well if the rings or valve guides have gone, it will involve a lot of stripping down. It would be much easier just to get a whole new engine, they are not that expensive either as far as I know.

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Give it a service, give it a few good runs, and if it still smokes, ignore it until it gets terminal.

CG engines are tough. They sound like a bag of nails from day one, and the clearances are fairly loose so they can smoke a bit, but they go on and on.

badlydamaged · Spanner Monkey Joined: 29 Apr 2004 Karma :

Big Pete · Spanner Monkey Joined: 18 Jul 2004 Karma :

if you google David Silver Spares (Honda specialist), you can check the price of parts online. If it need a rebore you will need a full piston kit (piston, rings, gudgeon pin and clips) and a top end gasket set. Rebores tend to be around £10-15 per cylinder. If you have a manual and a few tools its not that bad a job, and its a good learning experience. Valve guides are a bit more of a pain, but still not a massive job (all tho you will need to get a special drift made). Its only a single cylinder bike after all. Thinking about it is far worse than actually doing it. Thumbs Up

However, if the engine has stood for while, as has been said before, give it a service and then just ride it for a while.

Last but not least, I wouldnt buy another engine from the breakers, there is a good likelihood that the motor is no better, and for the same money you could rebuild yours.
____________________
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pb399 · L Plate Warrior Joined: 03 Aug 2004 Karma :

It's been run pretty consitently for the past year - my brother had it before me, so it is likely it's been thrashed pretty hard! 16k does seem a little low to be needing a rebore though. I'll give it a service and see how things go - maybe have a closer look at the manual.

pb399 · L Plate Warrior Joined: 03 Aug 2004 Karma :

Right, the rvice didn't really help so I've decided to bite the bullet and fix it myself! Found all the parts on david silver spares (thanks Big Pete) and had a chat with a guy who's done the same job on his CG.

He reckons the bore should be ok with this many miles and I just need a deglaze. I've heard that you can deglaze the cylinder by hand with a scotchbrite pad - anyone know if this is ok or do I need to buy a cylinder hone? Also if I need a hone then what's better, a ball or shoe hone?

pb399 · L Plate Warrior Joined: 03 Aug 2004 Karma :

emm that should be the service didn't help much Confused

ts50x0 · Spanner Monkey Joined: 16 May 2004 Karma :

if your thinking of getting a new engine anyway then just ignore it and keep an eye on the oil level. if it goes bang(practicaly unheard of for a cg) then just put a new engine in then.

surly it cant smoke as much as an nsr anyway???????? Razz

TheShaggyDA · Repost Police Joined: 14 Jun 2004 Karma :

pb399 · L Plate Warrior Joined: 03 Aug 2004 Karma :

Finally bit the bullet and replaced the rings last weekend - job went ok except for a few tricky to remove gaskets and one sheared nut that somehow I was able to get out with a pliers Laughing

! The piston and cylinder had a small amount of vertical scoring but I ignored it for the minute and put it back together anyway.

First few kicks, nothing happened...then I remembered to reconnect the spark plug Rolling Eyes

Another 10 or so kicks before I noticed the fuel tap was still turned off...

Then it started on the third go!! No smoke, quiteter running and feels like it's got a bit more power, though I'm still running it in. Broke the kickstart lever off this morning but besides that there's been no trouble - it's easy to bump start anyway.

Thanks everyone for the help and encouragement Thumbs Up

Frost · World Chat Champion Joined: 26 May 2004 Karma :

If it wasnt for bad luck, you'd have no luck at all! Wink

palmer · Fiddled Kiddy Joined: 21 Jul 2004 Karma :

haha, had fun reading this topic

ZRX61 · Victor Meldrew Joined: 05 Nov 2003 Karma :

mchaggis · World Chat Champion Joined: 10 May 2004 Karma :

RooRoo · Anal Intruder Joined: 04 May 2004 Karma :