why has my exhaust got louder and ive lost overall power , dtr 125 ?

[dtr1252001]

So I was driving along like an idiot had a lil off the line race with another dtr, I got too near my house when the exhaust made a deep grunt , next thing I look and there is a hole in the exhaust next to the manifold ( I think that's what its called ) ( the bit near to the piston ) so my dad took the thing to work , welded it back as a temporary fix until I get a new expansion chamber , now before the bike was quiet and had more power , now its loud , the power valve is defonetely functional , I know they're generally louder when pinned open , the valve still works its just lost overall grunt and isn't as quiet ? Any ideas ? Has my dad restricted it somehow , or is it just because he's welded it and its probably weaker resulting in some sort of minor hole / power loss ?

[Cynic]

Any air leak will mess with a 2stroke. The exhaust is one of the most important parts.

If you have the stock chamber its double skinned which is prob messing the gas flow.

[dtr1252001]

So am I right in thinking that what you mean is , because my dad has welded a small area of the chamber , its not all the same thickness now and so there's probably some sort of leak causing the more sound and loss of power? Alternatively. , because one part is now weakened it vibrates more making more sound and probably messing with the back force that the chamber provides ? Sorry not sure what u mean u weren't really specific , you just said that the standard chamber is dual layered , but obviously before the hole it as alright so I've taken my own assumptions based on that its a dual layered chamber ?

[gizmo666]

now its loud

that tells you right away the exhaust is not suppressing the sound therefore not suppressing the exhaust gases

reason 1 baffle faulty

2 hole in the exhaust

method of repair 1 replace the baffle or baffle material

2 replace the exhaust or find and plug the hole

[Noise]

May find that "if" your exhaust is double skinned your dad may have welded the outer metal but not the inner skin, thus making a void between the two layers for the exhaust to fill.

DO NOT DO THE FOLLOWING WITH A HOT EXHAUST

Start up your bike.

Stick your hand over the end of the exhaust to block the gas coming out

Make sure your pushing hard enough to stop the exhaust gas coming out

Now listen to see if you can here a pulsing hiss like exhaust gas is coming out of either the header / hole

If its plowing out of your hand then assuming you are pushing enough to block it coming out then you have no holes in your exhaust therefor no leaks

PS you can use this trick to see if you have a blow in your exhaust one all engines.

Just don't block it for too long

[Cynic]

The welding will play havoc with the gas flow too causing all sorts of bad reflections.

Replacement is best. If its bad enough to blow out there will be other leaks. With a 2 stroke you have to be sure there are no air leaks so air can get IN either or it ruins the mix and goes lean. Which also makes the engine louder wierdly.

[Alexengongong]

It has lost performance as 2 strokes rely on the exhaust back pressure to 'suck' the exhaust gas out of the combustion chamber as they dont have valves and a 'forth stroke' to force any gases out like a 4T engine. The best thing to do like Cynic said is to replace it as the damage might be worse than just a hole on the outside, but actual damage to the inside... Thus making it louder and perform worse than normal.