Exhaust problem

[Alexio]

Hi. I own a Honda cg 125cc which recently started to sound terrible and lose power so my friend did a compression test on it. It got just 55psi so I was assuming it was a piston ring problem or valve problem etc.

However, I've just discovered two small holes in the exhaust where it connects to the engine, which would explain why it's a bit louder and sounding worse, and even why some power is lost, but would this explain a loss of compression in my cylinder? I'm still concerned there's something wrong with the engine as well, and yes it does have enough oil in it.

Thanks.

[Jeansy001]

well fix the exhaust and run another test. a hole in the exhaust will make the engine lose pressure, hense the reason it loses power. all your going to need is a set of downpipes
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CBR 400RR,cant get much more fun than that on the road

[Alexio]

You're right, I should endeavour to fix my exhaust first as this is the best diagnostic course of action.

If you happen to be curious though, this is what really happened: It was stolen, ridden around a field for a day before being dumped, recovered and finally returned to me. I've fixed what cosmetic damage there was but the engine was definitely abused (ragged to hell probably) by who ever stole it. I'm curious as to how abusing my engine could create those holes in the exhaust though, except for excess heat applied to an already weak part of a joint.

I'm just really hoping once the exhaust is fixed it'll all be ok, but it wouldn't hurt to look inside then engine and inspect I suppose?

[Jeansy001]

well a small bike like the honda CG shouldnt have too much engine damage, their built to be reliable and withstand idiots. just sort the exhaust out first and the take it to the garage for a routine service. they will check to make sure everything is totally fine, if not they will give a proffesional diagnosis and opinion on what you should do
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CBR 400RR,cant get much more fun than that on the road

[Alexio]

Thanks for the advice It's weirdly hard to be objective sometimes when just wanting your bike working how it used to.

[Jeansy001]

yea, best thing is dont rush it. take your time and make sure its fully recovered from its kidnapping othewrise it could end up poorly again. i thin the new pipes will sort her out just fine though
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CBR 400RR,cant get much more fun than that on the road

[Odie]

[Alexio]

Thank you Odie, this is what I was afraid of. I'll get it checked out as soon as I can.

[Noxious89123]

What Odie said
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'06 Honda CBR125RW-6 ~ '00 Honda CBR600F-Y ~ '07 Honda CBR600RR-7 ~ Bikeless
'53 Ford Ka 1.3 ~ '03 Vauxhall Astra SRi 1.8 ~ '52 Vauxhall Astra SRi 2.2 ~ '53 Vauxhall Astra GSi

[Alexio]

Well, I still haven't gotten around to diagnosing it further yet seeming as it's still just about hanging on to life. The small exhaust holes are on the manifold and apparently just £10 to fix.

But I hope I'm not potentially doing any further damage to it as I really don't have any more money to fix my piston and or valves when this turns out to inevitably be the problem

Still CG's are tough things, it'll pull through.

[Alexio]

Right so this is what I've done today;

squirted oil through the spark plug hole and did another compression test. Got closer to 90psi this time instead of 55. I also removed the top of the engine to peek at the valves and it looks clean in there (no carbon or anything) so my assumption at this point is definitely something wrong with my piston rings and not the valves.

A piston kit for my bike is about £35 - £40. However, what if my bore or head is damaged? I could also use this opportunity to have my engine re-bored anyway?

My friend tells me that he has a scrap bike with a (probably) identical engine that he could transplant parts from. Does this sound like a good idea?! We checked the engine model numbers and they are the exactly the same except the last number by it's self (5 instead of 4) and the main part of the engine block does look exactly the same.

[Alexio]

Just a bump on this thread to say my bike is all fixed now

After having my exhaust fixed, everything is suddenly and magically fine. The person that welded my exhaust back to health did another compression test for me and got near 150PSI and told me that when I was doing it I probably wasn't holding the throttle open and therefore doing it completely wrong would have been nice if anyone else I had talked to could have told me that

What I'm the most surprised about is that my bike definitely has more power now. I'll have to wait until I fix the last thing broken on my bike, my speedo, until I know for sure if it's the same as it ever was. Anyway, I'm very, very happy

Now where to find a speedo cable...
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will never give up his CG. I look at my fuel gauge more as a progress bar than a fuel gauge.
G: With my GSXR I do often effectively use it as a scooter with a clutch in town.
ms51ves3: why does it need 500 miles? Are you teaching it how to be a piston?