little bit more speed?

[speedjunkie20...]

Just got the hole in the exhaust sorted, full comprestion in the exhaust, my top end is 65mph, was just wondering if there any way of getting a little bit more out of it. Its a dt125r 1996 model btw, with a big one exhaust fitted and powervalve fitted.

[Irn-Bru]

Removed the restrictor from the exhaust?

[speedjunkie20...]

im not sure where the restrictor is on this exhaust? none of the parts have been fitted by myself it was all like this when i bought it

[st3v3]

[speedjunkie20...]

Yeah, got the reciepts from the garage having fitted it, and you can feel it kick in at 8k revs

[binge]

Should be doing 75mph easily then. Probably more like 80mph on a DT125 I'd of thought.



Ben

[speedjunkie20...]

yeah tis what i thought, it gets to 65 f*****g quick, but then just seems when you go into sixth, the revs drop and it stops accelerating at all?

[binge]

Sounds like its dropping out of the powerband when you hit 6th gear.

A quick fix would be fit a smaller front sprocket.
This will make it accelerate faster, But it will also increase the torque, helping it rev out in 6th gear.


I dont really understand 2t tuning myself, But I know that different expansion chambers affect the way the powerband is delivered.

Some spanny chambers give you a really long but subtle power band. And some spanny chambers (Like the one on my pit bike), Give you a really short, But fucking punchy power band.


If you've changed the pipe from standard, It could be that the powerband period has moved up the rev range. In which case a smaller front sprocket will sort it right out.




Ben

[tonyts50]

bigger carb
and sproket it ! i would say just 2 extra teeth on the front
____________________
tony ts50 gone from off road to on road to back off road cat c write off

why am i such a prick !!!! im such a fucking soppy bollocks

[Blau Zedong]

[MarJay]

Just fit a bigger carb, bigger exhaust, adjust the oil pump so it doesn't pump so much oil, and then pour TNT into the fuel tank as this will make your bike fasterer.

Kids don't seem to realise that engine tuning is not about bolting on performance parts, its about carefully measuring and seeing how you can improve an engine from the factory. If bike manufacturers could get more speed just by bolting on a bigger carb etc, then we'd all be riding CB750's with vaaast carburettors wouldn't we?

This, however, is not a case of engine tuning. The bike should have a reasonable performance to begin with so we're into fault finding rather than tuning. In this case, I'd say that changing the carb is about the last thing you want to do. I'd say start by making sure the air filter is clean and free from holes. Then I'd check that the powervalve moves freely and is adjusted correctly. Then I'd check stuff like tyre pressures, chain tension etc. I might even change the spark plug to a new standard spark plug. (NOT iridium). I would also try a plug chop to see if the bike is running rich or lean.

Then, I'd remove the exhaust and have a look up the exhaust port. I'd put my fingers on the piston skirt to see if it moves backward and forward in the bore. If it does, the bike needs a rebore. I'd then move the piston down with the kickstarter (keeping fingers clear of the exhaust port) and shine a light into the bore to try to determine the state of the liner, and to see if there is any other damage.

After that, I'd consider stripping the top end of the engine to see if it needs a rebore or new rings etc. Whilst its stripped, It may as well have a new piston and rings, and a new little end bearing unless the bike has been recently rebuilt.

To be honest, I'd be tempted to give the bike a damn good service, and then possibly try Binge's suggestion of a 1 tooth smaller front sprocket before I started taking stuff off the bike. But then, I am a lazy sod.
____________________
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.