CG125 gone POP!!!

[Johnster]

Hi All,

When i set off from Work yesterday eve to go home i noticed my little CG was underpowered (Well, more than usual anyway) Putting this down to a headwind whilst traveling down the motorway i thrashed the knackers off the poor thing.

About 1 mile from home i noticed the engine seemed louder than normal and as i reached the exit slip road off the motorway all power was lost and the bike ground to a halt.

The engine will not start and when i kick there does not seem to be as much resistence as there was before.

Looking at the engine there is a small amount of oil that has seeped out of where the bottom gasket is. Otherwise nothing out of the ordinary.

Sounds like a blown bottom gasket leading to loss of compression to me but i was just wondering if anyone has any other ideas before i strip down.

Cheers again guys

John

[stinkwheel]

There's definately oil in it? Running out of oil is about the only way I can think of killing a CG.

Having a look at the plug electrode may give you a clue as to what has happened. If it's down on compression you may have dropped a valve or holed the piston. If you've holed the piston the sparkplug will be looking decidedly the worse for wear.

A CG being so inherantly unbreakable, it is also possible one of the tappets has tightened up on you and is holding a valve open (which would take a matter of minutes to fix). This would explain the earlier lack of power too.

So check the plug, then whip the inspection covers off and have a look at the tappets for signs of them closing up or a dropped valve.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Johnster]

Cheers for the reply.

Definatley oil in, i check regulary.

I will be stripping down over the weekend and will check the tappets, I wouldnt have thought this would account for oil leaking from the bottom gasket though?

As i say, when i kick slowly its as if most of the resistance has gone so definatley a loss of compression.

[0ddball]

It will be interesting to see what went wrong.

But at least you can sling in another engine for £50.
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ZXR750L

[stinkwheel]

Oil leaking out of the base gasket is unlikely to be what's caused the problem unless it's got to such an extent as to cause a drop in oil levels/pressure. Would be an issue on a 2-stroke but not on a CG.

I've seen the barrels on an old push-rod BSA so loose that you could literally see them moving up and down as the engine ticked over.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[MarJay]

Is it a genuine Honda CG, and not a copy?
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F; Cheap project: CBR900RR FireBlade
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Wafer_Thin_Ham]

Honda CG's don't go pop. It's a fake I tell thee!
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[Johnster]

Engine for £50! Bargain! Where would i get one of those then?!? Cheapest i've seen on Ebay are about £100

Its a geniune Honda Brazil engine but has covered 60k so its getting a little tired im guessing.

Would it just be easier to buy another engine and stick it in do you think?

[Wafer_Thin_Ham]

Depends what's gone. It's only a CG engine so it can't be THAT complex.
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[Johnster]

Actualy, I forgot to mention. The oil around the bottom gasket was not present before the engine died therefore this must have something to do with what has gone wrong with the engine!

[Johnster]

Hi Guys,

Just thought i'd give you an update as to the root of the CG's problems.

I stripped the top end down and discovered to my horror the extent of the damage!

Both the barrel and the piston are scratched to hell and one of the piston rings had snapped. This would account for poor performance before the engine blew and lack of compression when the piston ring snapped i am guessing???

I'll post some photos so you can see the damage!!!

Anyway, bought myself a piston kit, head with barrel and gaskets and am going to put back together this weekend.

before i do this i need to clear the coke from the valves and the roof of the cylinder Can anyone suggest a better way of doing this than using a screwdriver to chip it off? lol

Cheers,

john

[lukamon]

lots of wd - 40 and a lolly stick, like in a magnum.
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killa wrote: Im an ass man myself

[Johnster]

Thanks. I guess it has the added bonus of eating the magnum beforehand!

[SilvaRizla]

CG125 + Motorway.....



Are you mental man?!?!?!
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I'm Ivan Dobski the Meatsafe Murderer only I never done it, I only said that I done it so they'd take the truncheon out of my bottom

[stinkwheel]

Or you can saw a split along one side of the last 1/2" of a short piece of copper pipe. Bend the split bit open like a spoon and hammer it flat. Hey-presto, one scraper.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[SilvaRizla]

hehe, where you thinking of that for a while Stink?
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I'm Ivan Dobski the Meatsafe Murderer only I never done it, I only said that I done it so they'd take the truncheon out of my bottom

[Johnster]

lol Whats wrong with a CG on the motorway?

[Johnster]

Heres a couple of pics showing each side of the piston. As you can see it is in quite a state.

As the pic was taken with my camera phone its poor quality and the photo dosent show the deep indents carved in the supposedly smooth surface!!!!

[Johnster]

View from the other side!!

[Rockhopper]

Before you waste your money on those shiny new parts you need to find out why the thing went bang in the first place or it'll just happen again! Bits of piston missing might hint at detonation so you may have a mixture or ignition timing problem.

[Johnster]

I think the engine has just become tired as it has done about 62k miles and has never been rebuilt.

WHilst running it burned oil quite badly and the power seemed restricted. Im assuming this was because of the damage to the side of the piston, possibly caused by low oil levels..

WHen it went POP traveling down the motorway, Im pretty sure this was the piston rings breaking up causing severe loss of compression.

The engine did start after the incident by bumping it but the engine didnt produce much power i.e. not enough to move the bike without stalling!

Im gonna fir the new piston etc and see how it goes!

Wish me luck!

[Lone-Wolf]

[speedster]

I used to use a 2p coin to decoke, same idea as the copper pipe mentioned, Fast solution for small jobs.

[bladerunner]

62K miles and its never had a rebuild!! Fair do's..I never did manage to blow my old jap CG just bust 3rd gear and wear out 2 genny coils!!

[SilvaRizla]