'97 KTM lc2/sting

[rraleks]

Thanks for all the input! The jetting required for derestricting (supposedly) is Mainjet from size 132 to 152 and raise the needle one step. my Mainjet is now 168, the needle raised one step, and I've also increased idle jet from 50 to 60 or so.

Carburettors are complicated devices it seems.It is clean as a whistle, and the thermostat is tested with most of all the other issues sorted out, I will raise the needle further one step to see what happens. Then it is necessary to get a new atomiser/ needle combo if I want more fuel in the main circuit.
The Aprilia rs125 use a smaller mainjet combined with a atomiser/needle that delivers more fuel for the high output versions.

[MadGyver]

@rraleks Forget what RS125 has,different engine.Even two 125's with same carb settings,same engine but different porting have different behavior,one may be lean and the other too rich.

[HOTSHOT III]

@MadGyver Agreed. Maybe see if the TDR125 or TZR125R Belgarda models have the same Dell'Orto carb as the LC2 and get an idea of the jetting from there

[markus.w]

@rraleks but yours is a DT125r engine. Nothing at all like a rs125 engine, albeit with a different carb so you can't compare it to either of them.

[markus.w]

@HOTSHOT-III good call, I think some of them models do.

[SpookDog]

@rraleks

Jetting in no way affects restriction. Carb size yes, but not jetting. It’s the oldest boy racer miss information that I know of...

You can’t even compare jetting to the same bike as different year models have different jetting. Even though the carbs are all Mikuni 28mm’s!...

Return your bikes carb to standard jetting for its year before you go any further. Please!...

Then check your cooling, radiator coolant level, thermostat, ect...

[rraleks]

@SpookDog Well that is a recipe for disaster I'm afraid. It would lead to two holes in my piston if anything. If the engine is running lean it would sure not help to lean it even more? Smaller jets and a tighter fit for fuel in the atomiser sure would do so, would you disagree?

[Calum]

@rraleks I think the point being, it doesn't sound rignt.

Are you modified or bog standard?

If it's standard then you should be running stock jetting.

[rraleks]

@Calum Oh no, it is not standard. The restrictions are gone and my crank seems to have longer stroke. 56 from standard 50,68 i think. This is where the problems started my brother said. Now I have also some holes in the airbox, a set of Boyesen reed-flaps and a pipe without a cat. The athena kit have 56mm bore, so that's pretty standard.

[Calum]

@rraleks probably running waaaayy too much compression then if the strokes increased.

Have you got a compression tester?

[SpookDog]

@rraleks

Who says it’s running lean? Overheating is caused by different things, lean is one possibility only. Check your radiator coolant level please mate...

No way the crank has a 5.5mm longer throw! It’d of locked solid against the head...

Please check your radiator coolant level!...

I ran my bike well lean for 1000’s of miles without damaging the piston. It was only when my head gasket blew and emptied my radiator that it ran it hot enough to eat the piston, in the same way as yours...