Dt 125re 2005 no power, feels flat

Ballsdeep69 · L Plate Warrior Joined: 29 Jun 2020 Karma :

Hi everyone I am Andrew and I have a dt 125 re 2005 which feels really flat. I have just put a new piston and rings in, done the crank seals etc. It ticks over smooth and drives through all the gears but is really lagging in power in ever gear. I have pinned the power valve open half way to try that but it is still flat. You open it up we're it starts to get going but just bottoms out on the revs change gear bottoms out again. When you put full throttle out and max it to the top it starts to miss like it's not sparking right or not getting enough fuel to give it that extra power. does not have that power valve type feeling on it. I can ride it about round the doors but it is so flat. Only Doing about 40 mph top end

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Have you given it a dose of caustic soda down the exhaust at all?
maybe it's all gummed/coked up.
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Easy-X · Super Spammer Joined: 08 Mar 2019 Karma :

Ballsdeep69 · L Plate Warrior Joined: 29 Jun 2020 Karma :

[quote="Easy-X"][quote="WD Forte"]Have you given it a dose of caustic soda down the exhaust at all?
maybe it's all gummed/coked up.[/quote]

And of course, at the other end how's the air filter?

Nice nickname. I'm guessing you're a youngster :)[/quote]
Tried a new one mate.

Ballsdeep69 · L Plate Warrior Joined: 29 Jun 2020 Karma :

[quote="WD Forte"]Have you given it a dose of caustic soda down the exhaust at all?
maybe it's all gummed/coked up.[/quote]

Yes tried another exhaust also.

A100man · World Chat Champion Joined: 19 Aug 2013 Karma :

Cable routing, throttle slide opening fully?
Carb clean and check jet sizes ?
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redeem ouzzer · World Chat Champion Joined: 06 Oct 2015 Karma :

Piston Clearance?
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Fizzer Thou · World Chat Champion Joined: 06 Aug 2011 Karma :

Is the gasket between the reed valve block and the barrel in good condition?

Is the reed valve in good condition?

Have you tried a new plug cap?
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jeffyjeff · World Chat Champion Joined: 02 May 2020 Karma :

Besides checking the reed valve and carburetor slide, you might also consider some additional possible causes of your low power condition:
1. Fuel flow to the carburetor could be restricted.
2. Tank vent could be clogged, resulting in low fuel flow to the carburetor.
3. Carburetor main jet could be obstructed or gummed up (especially true if the bike has been sitting for an extended period)
4. Carburetor float could be set improperly, or the float valve could be stuck or obstructed.
5. Weak spark or problems with ignition timing advance might also affect your high end performance.

Good luck with your troubleshooting. Let us know what you find.
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Robby · Dirty Old Man Joined: 16 May 2002 Karma :

Drain the carb and see what comes out, I have symptoms like this from water in the carb before. Its works OK on the pilot jet which is pickup up fuel from the top of the float bowl, but when you get on to the main jet it's picking up a mixture of fuel and water from the bottom of the bowl.

Lots of simple things that it could be. Lots of more complex things as well - this is a recently rebuilt 125, I have no idea about your mechanical competence, so I have to assume you may have cocked up something on the rebuild.

As mentioned, a new spark plug and cap never hurts. I'm assuming the two-stroke oil system is working properly and it has oil in the bottle.